ASTM F1281-24

Standard Specification for Crosslinked Polyethylene/Aluminum/Crosslinked Polyethylene (PEX-AL-PEX) Pressure Pipe

ABSTRACT
This specification covers coextruded cross linked polyethylene composite pressure pipe with welded aluminum tube reinforcement between the inner and outer layers. The inner and outer cross linked polyethylene layers are bonded to the aluminum tube by a melt adhesive. Included is a system of nomenclature for the cross linked polyethylene-aluminum cross linked polyethylene (PEX-AL-PEX) pipes, the requirements and test methods for materials, the dimensions of the component layers and finished pipe, adhesion tests, and the burst and sustained pressure performance. Also given are the requirements and methods of marking. The pipe covered by this specification is intended for use in potable water distribution systems for residential and commercial applications, water service, underground irrigation systems, and radiant panel heating systems, baseboard, snow- and ice-melt systems, and gases that are compatible with the composite pipe and fittings. It covers only composite pipes incorporating a welded aluminum tube. The PEX-AL-PEX pipes are classified by the outside diameter. The pipe shall be free of visible cracks, holes, foreign inclusions, blisters, and other known injurious defects. The pipe shall be as uniform as practicable in color, opacity, density, and other physical properties.
SCOPE
1.1 This specification covers a coextruded crosslinked polyethylene composite pressure pipe with a welded aluminum tube reinforcement between the inner and outer layers. The inner and outer crosslinked polyethylene layers are bonded to the aluminum tube by a melt adhesive. Included is a system of nomenclature for the crosslinked polyethylene-aluminum-crosslinked polyethylene (PEX-AL-PEX) pipes, the requirements and test methods for materials, the dimensions of the component layers and finished pipe, adhesion tests, and the burst and sustained pressure performance. Also given are the requirements and methods of marking. The pipe covered by this specification is intended for use in potable water distribution systems for residential and commercial applications, water service, building supply lines, underground irrigation systems, and radient panel heating systems, baseboard, snow- and ice-melt systems, and gases that are compatible with the composite pipe and fittings.
Note 1: Piping covered by this specification is not recommended for use in indoor flammable gas applications.  
1.2 This specification covers only composite pipes incorporating a welded aluminum tube. Pipes consisting of metallic layers not welded together are outside the scope of this specification.  
1.3 Specifications for connectors for use with pipe meeting the requirements of this specification are given in Annex A1.  
1.4 This specification excludes polyethylene-aluminum-polyethylene pipes (see Specification F1282).  
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.6 The following precautionary caveat pertains only to the test methods portion, Section 9, of this specification: This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2024
• ICS: 23.040.20 - Plastics pipes
• Technical Committee: F17 - Plastic Piping Systems
• Drafting Committee: F17.11 - Composite

Relations

• Replaces: ASTM F1281-23a - Standard Specification for Crosslinked Polyethylene/Aluminum/Crosslinked Polyethylene (PEX-AL-PEX) Pressure Pipe
• Effective Date: 01-Feb-2024
• Refers: ASTM D2765-16(2024) - Standard Test Methods for Determination of Gel Content and Swell Ratio of Crosslinked Ethylene Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM E8/E8M-24 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 01-Jan-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM E8/E8M-22 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 01-May-2022
• Refers: ASTM D2765-16 - Standard Test Methods for Determination of Gel Content and Swell Ratio of Crosslinked Ethylene Plastics
• Effective Date: 01-Sep-2016
• Referred By: ASTM F2165-19 - Standard Specification for Flexible Pre-Insulated Plastic Piping
• Effective Date: 01-Feb-2024
• Referred By: ASTM F876-24 - Standard Specification for Crosslinked Polyethylene (PEX) Tubing
• Effective Date: 01-Feb-2024
• Referred By: ASTM F412-23 - Standard Terminology Relating to Plastic Piping Systems
• Effective Date: 01-Feb-2024
• Referred By: ASTM F2623-24 - Standard Specification for Polyethylene of Raised Temperature (PE-RT) Systems for Non-Potable Water Applications
• Effective Date: 01-Feb-2024
• Referred By: ASTM F1282-23a - Standard Specification for Polyethylene/Aluminum/Polyethylene (PE-AL-PE) Composite Pressure Pipe
• Effective Date: 01-Feb-2024
• Referred By: ASTM F3253-24 - Standard Specification for Crosslinked Polyethylene (PEX) Tubing with Oxygen Barrier for Hot- and Cold-Water Hydronic Distribution Systems
• Effective Date: 01-Feb-2024
• Referred By: ASTM F1974-23 - Standard Specification for Metal Insert Fittings for Polyethylene/Aluminum/Polyethylene and Crosslinked Polyethylene/Aluminum/Crosslinked Polyethylene Composite Pressure Pipe
• Effective Date: 01-Feb-2024
• Referred By: ASTM F2929-17(2021) - Standard Specification for Crosslinked Polyethylene (PEX) Tubing of 0.070 in. Wall and Fittings for Radiant Heating Systems up to 75 psig
• Effective Date: 01-Feb-2024

Overview

ASTM F1281-24 is the internationally recognized standard specification for Crosslinked Polyethylene/Aluminum/Crosslinked Polyethylene (PEX-AL-PEX) Pressure Pipe, developed by ASTM International. This specification covers the requirements, test methods, and classification system for PEX-AL-PEX composite pressure pipes comprising coextruded layers of crosslinked polyethylene and a welded aluminum tube reinforcement. The inner and outer PEX layers are bonded to the aluminum core using a melt adhesive. These pipes are designed primarily for use in potable water distribution systems, building supply lines, underground irrigation, radiant heating, baseboard, and snow- and ice-melt systems, as well as compatible gas applications.

Key Topics

• Material Composition:

  • PEX-AL-PEX pipe consists of two crosslinked polyethylene layers, a welded aluminum core, and layers of melt adhesive bonding the PEX to the aluminum.
  • Only pipes with welded aluminum layers are covered under this standard.

• Performance Requirements:

  • Requirements for material properties, including minimum elongation and tensile strength for aluminum.
  • Specifications for crosslinking and gel content for inner and outer PEX layers.
  • Dimensional standards for component layers and overall pipe dimensions.
  • Strict criteria for wall thickness, diameter, and out-of-roundness.

• Testing Methods:

  • Adhesion tests for PEX and aluminum layers.
  • Burst and sustained hydrostatic pressure performance tests.
  • Apparent tensile strength, ring strength, and gel content evaluations.
  • Special tests for chlorine resistance when used in disinfected water systems.

• Marking and Quality Assurance:

  • Pipes must be clearly marked with manufacturer information, standard designation, size, pressure and temperature ratings, and suitability for potable water.
  • Legibility of markings after installation is required for compliance.
  • Comprehensive quality assurance protocols include sampling and conditioning guidelines.

Applications

PEX-AL-PEX pressure pipes are utilized in a variety of environments due to their flexibility, durability, and resistance to corrosion and scaling. Primary applications include:

• Potable Water Distribution:
  Certified for residential and commercial plumbing, providing long-lasting, clean water transport while resisting leaching and corrosion.

• Heating and Cooling Systems:
  Widely used in radiant floor heating, baseboard heating, and snow- and ice-melt systems because of high temperature and pressure resistance.

• Underground Irrigation:
  Suitable for subterranean applications, offering stable performance under variable soil and climate conditions.

• Building Supply Lines:
  Used for main water supply lines within buildings due to robust mechanical properties.

• Gas Distribution (when compatible):
  Applicable for certain gases, provided they are compatible with the composite structure and fittings.
  Note: ASTM F1281 PEX-AL-PEX piping is not recommended for indoor flammable gas applications.

Related Standards

Understanding the broader regulatory context is beneficial for proper implementation and compliance. Related standards include:

• ASTM F1282: Specification for Polyethylene/Aluminum/Polyethylene (PE-AL-PE) Composite Pressure Pipe-governing composite pipes without crosslinking.
• ASTM F1974: Specification for metal insert fittings compatible with PEX-AL-PEX and PE-AL-PE pipes.
• ASTM D3350: Specification for polyethylene materials used in pipe production.
• ASTM D1598 & D1599: Test methods for sustained and burst pressure evaluations of plastic pipes.
• NSF/ANSI Standard 61 & 14: Certifications for drinking water system components, ensuring health and safety compliance.
• Annexes and Supplemental Requirements:
  • Connector requirements for assemblies.
  • Additional provisions for federal or military procurement.
  • Chlorine resistance evaluation for pipes in disinfected water systems.

Practical Value

Adopting ASTM F1281-24 PEX-AL-PEX ensures high performance in demanding water and heating system environments. The multilayer construction offers a unique combination of strength, flexibility, and corrosion resistance, making it preferred for modern plumbing, radiant heating, and hydronic applications. Compliance with ASTM F1281-24 supports quality assurance, installation safety, long-term durability, and regulatory acceptance in both commercial and residential projects. This standard remains central to the reliable, sustainable use of composite piping in infrastructure and building systems.

Keywords: PEX-AL-PEX, ASTM F1281-24, crosslinked polyethylene, aluminum, composite pressure pipe, potable water piping, radiant heating pipe, plumbing standards

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F1281 − 24 An American National Standard
Standard Specification for
Crosslinked Polyethylene/Aluminum/Crosslinked
Polyethylene (PEX-AL-PEX) Pressure Pipe
This standard is issued under the fixed designation F1281; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* if any, associated with its use. It is the responsibility of the user
of this standard to establish appropriate safety, health and
1.1 This specification covers a coextruded crosslinked poly-
environmental practices and determine the applicability of
ethylene composite pressure pipe with a welded aluminum tube
regulatory limitations prior to use.
reinforcement between the inner and outer layers. The inner
1.7 This international standard was developed in accor-
and outer crosslinked polyethylene layers are bonded to the
dance with internationally recognized principles on standard-
aluminum tube by a melt adhesive. Included is a system of
ization established in the Decision on Principles for the
nomenclature for the crosslinked polyethylene-aluminum-
Development of International Standards, Guides and Recom-
crosslinked polyethylene (PEX-AL-PEX) pipes, the require-
mendations issued by the World Trade Organization Technical
ments and test methods for materials, the dimensions of the
Barriers to Trade (TBT) Committee.
component layers and finished pipe, adhesion tests, and the
burst and sustained pressure performance. Also given are the
2. Referenced Documents
requirements and methods of marking. The pipe covered by
2.1 ASTM Standards:
this specification is intended for use in potable water distribu-
D618 Practice for Conditioning Plastics for Testing
tion systems for residential and commercial applications, water
D883 Terminology Relating to Plastics
service, building supply lines, underground irrigation systems,
D1598 Test Method for Time-to-Failure of Plastic Pipe
and radient panel heating systems, baseboard, snow- and
Under Constant Internal Pressure
ice-melt systems, and gases that are compatible with the
D1599 Test Method for Resistance to Short-Time Hydraulic
composite pipe and fittings.
Pressure of Plastic Pipe, Tubing, and Fittings
NOTE 1— Piping covered by this specification is not recommended for
D1600 Terminology for Abbreviated Terms Relating to Plas-
use in indoor flammable gas applications. 3
tics (Withdrawn 2024)
1.2 This specification covers only composite pipes incorpo-
D1898 Practice for Sampling of Plastics (Withdrawn 1998)
rating a welded aluminum tube. Pipes consisting of metallic
D2122 Test Method for Determining Dimensions of Ther-
layers not welded together are outside the scope of this
moplastic Pipe and Fittings
specification.
D2765 Test Methods for Determination of Gel Content and
Swell Ratio of Crosslinked Ethylene Plastics
1.3 Specifications for connectors for use with pipe meeting
D3350 Specification for Polyethylene Plastics Pipe and Fit-
the requirements of this specification are given in Annex A1.
tings Materials
1.4 This specification excludes polyethylene-aluminum-
E8/E8M Test Methods for Tension Testing of Metallic Ma-
polyethylene pipes (see Specification F1282).
terials
1.5 The values stated in SI units are to be regarded as
F412 Terminology Relating to Plastic Piping Systems
standard. The values given in parentheses after SI units are F1282 Specification for Polyethylene/Aluminum/
provided for information only and are not considered standard.
Polyethylene (PE-AL-PE) Composite Pressure Pipe
F1974 Specification for Metal Insert Fittings for
1.6 The following precautionary caveat pertains only to the
Polyethylene/Aluminum/Polyethylene and Crosslinked
test methods portion, Section 9, of this specification: This
Polyethylene/Aluminum/Crosslinked Polyethylene Com-
standard does not purport to address all of the safety concerns,
posite Pressure Pipe
1 2
This specification is under the jurisdiction of ASTM Committee F17 on Plastic For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Piping Systems and is the direct responsibility of Subcommittee F17.11 on contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Composite. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Feb. 1, 2024. Published February 2024. Originally the ASTM website.
approved in 1990. Last previous edition approved in 2023 as F1281 – 23a. DOI: The last approved version of this historical standard is referenced on
10.1520/F1281-24. www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1281 − 24
2.2 National Sanitation Foundation Standard: the thickness of the wall of the pipe. The PEX-AL-PEX pipes
Standard No. 61 Drinking Water System Components— have a hoop stress distribution that differs substantially from
Health Effects both the thick and thin walled pipe cases.
Standard No. 14 Plastics Piping System Components and
Related Materials
4. Pipe Classification
2.3 Federal Standard:
4.1 Pipe Diameter—The PEX-AL-PEX pipes are classified
Fed. Std. No. 123 Marking for Shipments (Civil Agencies)
by the outside diameter.
2.4 Military Standard:
4.2 Pipe Dimension Ratio—The concept of dimension ratio
MIL-STD-129 Marking for Shipment and Storage
is not relevant to PEX-AL-PEX composite pipes, and cannot
2.5 Uniform Classification Committee Standard:
6 be used to relate pressure rating with total wall thickness.
Uniform Freight Classification
2.6 National Motor Freight Traffıc Association Standard:
5. Materials
National Motor Freight Classification
5.1 General—The PEX-AL-PEX pipe is composed of one
3. Terminology
metallic layer, two layers of polymeric adhesive, and two
3.1 Definitions—Definitions are in accordance with Termi-
layers of crosslinked polyethylene. For pipe made to this
nology F412, and abbreviations are in accordance with Termi- specification the constituent materials must meet the following
nology D1600, unless otherwise specified. requirements:
3.2 Definitions of Terms Specific to This Standard: 5.2 Aluminum—The aluminum shall have a thickness as
3.2.1 assembly—the joint between a fitting and a length of
specified in Table 1. The material shall have minimum elon-
pipe. gations and ultimate tensile strengths of 20 % and 100 MPa
(14 600 psi), respectively. The tests shall be conducted accord-
3.2.2 PEX-AL-PEX pipe—composite pipe produced by co-
ing to Test Methods E8/E8M.
extrusion or extrusion of layers of polyethylene/aluminum/
polyethylene bonded together with a melt adhesive and cross-
5.3 Crosslinked Polyethylene:
linked by irradiation or chemical means in combination heat
5.3.1 The polyethylene shall be, in the final finished state in
and moisture.
the pipe, crosslinked as defined in Terminology D883.
5.3.2 Polyethylene plastics used to make pipe meeting the
3.2.3 pipe hoop stress—for simplicity the value of the hoop
requirements of this specification shall be virgin resin meeting
stress quoted assumes a homogeneous wall. Local values of
the requirements of either Grade PE20A, B, or C; Grade
stress will vary with the different layers (see 3.2.3.1).
PE23A, B, or C; Grade PE30A, B, or C; or Grade PE33A, B,
3.2.3.1 Discussion—Thick walled plastic pipes produced
or C in accordance with Specification D3350.
from one material have hoop stresses that vary through the
5.3.3 Class B compounds shall have sufficient ultraviolet
wall, and are usually described by the Lame Theory. The
composite nature of the PEX-AL-PEX pipe, composed of (UV) stabilizers to protect the pipe from deleterious effects due
to continuous outdoor exposure during storage and shipping.
materials with very different Young’s Modulus values, will, on
pressurization, not have a uniform stress distribution through Pipe produced from Class B compounds are not suitable for
exposed outdoor application. Class A, B, and C compounds
shall have sufficient antioxidants to meet the requirements in
Available from NSF International, P.O. Box 130140, 789 N. Dixboro Rd., Ann
Specification D3350.
Arbor, MI 48113-0140, http://www.nsf.org.
Available from DLA Document Services, Building 4/D, 700 Robbins Ave.,
5.4 Melt Adhesive—The material shall have a density cell of
Philadelphia, PA 19111-5094, http://quicksearch.dla.mil.
1, 2, or 3; a melt index cell of 1, 2, or 3; and a color code of
Available from the Uniform Classification Committee, Suite 1106, 222 South
A or B, in accordance with Specification D3350.
Riverside Plaza, Chicago, IL 60606.
Available from the National Motor Freight Traffic Association, Inc., National
5.5 Rework Material—The use of reclaimed, recycled, or
Motor Freight Classification, American Tracking Associations, Inc., Traffic Dept.,
rework plastics is not permitted.
1616 P St., NW, Washington, DC 20036.
TABLE 1 Outside Diameters, Aluminum Thickness, and Tolerances for PEX-AL-PEX
Diameter Nominal
Minimum Outside Tolerance on Minimum, Maximum Out-of- Minimum Aluminum Tolerance on Thickness,
Nominal Pipe Size
A
Diameter, mm (in.) mm (in.) Roundness, mm (in.) Thickness, mm (in.) mm (in.)
(DN) (NPS)
12 ⁄8 12.00 (0.472) +0.30 (0.012) 0.3 (0.012) 0.18 (0.007) +0.09 (+0.0035)
16 ⁄4 16.00 (0.630) +0.30 (0.012) 0.4 (0.016) 0.18 (0.007) +0.15 (+0.006)
20 ⁄8 20.00 (0.787) +0.30 (0.012) 0.5 (0.020) 0.23 (0.009) +0.23 (+0.009)
25 ⁄4 25.00 (0.984) +0.30 (0.012) 0.5 (0.020) 0.23 (0.009) +0.09 (+0.0035)
26 ⁄8 26.00 (1.022) +0.30 (0.012) 0.5 (0.020) 0.53 (0.021) +0.10 (+0.004)
32 1 32.00 (1.260) +0.30 (0.012) 0.5 (0.020) 0.28 (0.011) +0.09 (+0.0035)
40 1 ⁄4 39.95 (1.573) +0.30 (0.012) 0.5 (0.020) 0.33 (0.013) .
50 1 ⁄2 49.90 (1.964) +0.30 (0.012) 0.5 (0.020) 0.47 (0.018) .
63 2 62.90 (2.484) +0.40 (0.016) 0.5 (0.020) 0.57 (0.022) .
75 2 ⁄4 75.10 (2.957) +0.60 (0.024) 1.0 (0.039) 0.67 (0.026) .
A
The out-of-roundness specification applies only to tubing prior to coiling.
F1281 − 24
6. Requirements 6.6 Sustained Pressure—The PEX-AL-PEX pipe shall not
fail, balloon, burst, or weep, as defined in Test Method D1598,
6.1 General—The requirements and test methods in this
when tested for 10 h at the test at the test pressure given in
specification cover PEX-AL-PEX pipes. Tests on the indi-
Table 5 at a temperature of 82 °C (180 °F) in accordance with
vidual layers that comprise this composite pipe are outside the
9.6.
scope of this specification. The raw materials used, however,
must conform to the requirements as set out in Section 5. 6.7 Gel Content—When tested in accordance with 9.7, the
gel content of the inner and outer tubes of crosslinked
6.2 Dimensions and Tolerances of Pipe:
polyethylene shall have minimum values of either 65 % for the
6.2.1 Pipe Diameter—The minimum outside diameter and
fully crosslinked silane material or 60 % for radiation cross-
tolerances of the pipe shall meet the requirements given in
linked polyethylene. Test Methods D2765 defines gel content
Table 1, when measured in accordance with 9.1 and 9.1.2.
(see Note 3).
Maximum and minimum (out-of-roundness) tolerances apply
only to measurements made on pipe prior to coiling.
NOTE 2—The gel test is one of several methods capable of indicating
6.2.2 Pipe Wall Thickness—The total pipe wall thickness the degree of crosslinking. The different methods for assessing degree of
crosslinking do not necessarily agree, so conformity to this specification
shall meet the requirements given in Table 2, when measured
requires degree of crosslinking to be determined in accordance with 9.7
in accordance with 9.1 and 9.1.3. The minimum wall thickness
only.
at any point of measurement of the pipe shall not be less than
the value specified in Table 2.
7. Workmanship
6.2.3 Inner and Outer Crosslinked Polyethylene Layer
7.1 The pipe shall be free of visible cracks, holes, foreign
Thicknesses—The thicknesses of the inner and outer layers of
inclusions, blisters, and other known injurious defects. The
crosslinked polyethylene in the PEX-AL-PEX pipe shall have
pipe shall be as uniform as practicable in color, opacity,
minimum values and tolerance as specified in Table 2, except
density, and other physical properties.
for the polyethylene material in the outer PEX layer overlaying
the weld, which shall have a minimum thickness of half those
8. Sampling and Conditioning
specified in Table 2. The polyethylene thicknesses shall be
measured in accordance with 9.2.
8.1 Sampling—Take a sample of the PEX-AL-PEX pipe
6.2.4 Pipe Length—The pipe shall be supplied coiled or in
sufficient to determine conformance with this specification.
straight lengths as agreed upon with the purchaser and with an
The number of specimens designated for each test shall be
allowable tolerance of −0 mm (−0 in.).
taken from pipe selected at random in accordance with the
random sampling plan of Practice D1898.
6.3 Adhesion Test:
6.3.1 For Sizes 0912 ( ⁄8) to 2532 (1) there shall be no
NOTE 3—Sample size and testing frequency of lots for quality control
delamination of the PEX and AL, either on the bore side or the
must be established by the manufacturer to ensure conformance to the
outside (see Fig. 1). The test shall be conducted in accordance
specification. Sampling and frequency will vary with the specific circum-
stances.
with 9.3.1.
6.3.2 The adhesion test of the PEX-layer to the aluminum
8.2 Test Specimens—Not less than 50 % of the test speci-
1 1
for Sizes 3240 (1 ⁄4) to 6075 (2 ⁄2) is carried out by a separation
mens required for any pressure test shall have at least part of
test. The minimum adhesive force is specified in Table 3. The
the marking in their central sections. The central section is that
adhesive force shall not fall below these levels. The test shall
portion of the pipe that is at least one pipe diameter away from
be conducted in accordance with 9.3.2.
an end closure.
6.4 Apparent Tensile Strength of Pipe—The pipe rings,
8.3 Conditioning—Condition the specimens at 23 °C 6
when tested in accordance with 9.4, shall meet the minimum
2 °C (73.4 °F 6 3.6 °F) and 50 % 6 5 % relative humidity for
strength specifications defined in Table 4.
not less than 40 h prior to test in accordance with Procedure A
6.5 Burst Pressure—The minimum burst pressure for PEX- of Practice D618, for those tests where conditioning is re-
AL-PEX pipe shall be as given in Table 4, when determined in quired. In cases of disagreement, the tolerances shall be 61 °C
accordance with 9.5. (61.8 °F) and 62 % relative humidity.
TABLE 2 Wall Thickness for PEX-AL-PEX Composite Pipe
Total Wall Wall Outer PEX Inner PEX
Diameter Nominal Nominal Pipe Size
Thickness, min, Tolerance Layer Thickness, Layer Thickness,
(DN) (NPS)
mm (in.) (+) mm (in.) min, mm (in.) min, mm (in.)
12 ⁄8 1.60 (0.063) 0.40 (0.016) 0.40 (0.016) 0.70 (0.028)
16 ⁄4 1.65 (0.065) 0.65 (0.022) 0.40 (0.016) 0.90 (0.035)
20 ⁄8 1.90 (0.075) 0.40 (0.016) 0.40 (0.016) 0.96 (0.038)
25 ⁄4 2.25 (0.089) 0.50 (0.020) 0.40 (0.016) 1.10 (0.043)
26 ⁄8 3.00 (0.118) 0.33 (0.013) 0.40 (0.016) 1.32 (0.052)
32 1 2.90 (0.114) 0.60 (0.024) 0.40 (0.016) 1.34 (0.053)
40 1 ⁄4 3.40 (0.134) 0.60 (0.024) 0.40 (0.016) 1.45 (0.057)
50 1 ⁄2 4.00 (0.157) 0.60 (0.024) 0.40 (0.016) 1.75 (0.069)
63 2 4.60 (0.181) 0.60 (0.024) 0.40 (0.016) 1.75 (0.069)
75 2 ⁄4 7.25 (0.285) 0.60 (0.024) 0.40 (0.016) 2.80 (0.110)
F1281 − 24
NOTE 1—(a) Good pipe showing no delamination, (b) Delamination between the inner layer and the aluminum, and (c) Delamination between the outer
layer and the aluminum.
FIG. 1 Detection of Delamination
TABLE 3 Minimum Adhesive Force for PEX-Al-PEX Composite TABLE 5 Minimum Sustained Pressure for PEX-AL-PEX
Pipe Composite Pipe
Minimum Adhesive Force per Diameter Nominal Pipe
Diameter Nominal Nominal Pipe Size Minimum Sustained Pressure PEX-AL-
10 mm (0.394 in.) Pipe Strip, Nominal Size
(DN) (NPS) PEX, kPa (psi)
N (lbf) (DN) (NPS)
1 3
40 1 ⁄4 40 (9.0) 12 ⁄8 2720 (395)
1 1
50 1 ⁄2 50 (11.2) 16 ⁄4 2720 (395)
63 2 60 (13.5) 20 ⁄8 2720 (395)
1 3
75 2 ⁄4 70 (15.7) 25 ⁄4 2720 (395)
26 ⁄8 2720 (395)
32 1 2720 (395)
40 1 ⁄4 2000 (295)
TABLE 4 Minimum Pipe Ring Strengths and 23 °C (73.4 °F) Burst 1
50 1 ⁄2 2000 (295)
Pressure of PEX-AL-PEX Composite Pipe
63 2 2000 (295)
75 2 ⁄4 2000 (295)
Minimum Pipe Minimum Pipe Minimum 23 °C
Diameter
Nominal Pipe Size Ring Strength, Ring Strength, (73.4 °F) Burst
Nominal
(NPS) Type II PE, Type III PE, Pressure, kPa
(DN)
N(lb) N(lb) (psi)
12 ⁄8 2000 (448) 2100 (470) 7000 (1020)
16 ⁄4 2100 (470) 2300 (515) 6000 (880)
the test methods or in this specification. In cases of
20 ⁄8 2400 (538) 2500 (560) 5000 (730)
25 ⁄4 2400 (538) 2500 (560) 4000 (580)
disagreement, the tolerances shall be 61 °C (1.8 °F) and 62 %
26 ⁄8 2400 (538) 2500 (560) 4000 (580)
relative humidity.
32 1 2650 (598) 2500 (560) 4000 (580)
40 1 ⁄4 3200 (719) 3500 (789) 4000 (580)
50 1 ⁄2 3500 (789) 3700 (832) 3800 (554)
9. Test Methods
63 2 5200 (1169) 5500 (1236) 3800 (554)
75 2 ⁄4 6000 (1349) 6000 (1349) 3800 (554)
9.1 Dimensions and Tolerances:
9.1.1 Pipe—Any length of the PEX-AL-PEX composite
pipe may be used to determine dimensions.
8.4 Test Conditions—Conduct the test in the standard labo- 9.1.2 Outside Diameter—Measure the outside diameter of
ratory atmosphere of 23 °C 6 2 °C (73.4 °F 6 3.6 °F) and the PEX-AL-PEX pipe in accordance with Test Method
50 % 6 5 % relative humidity, unless otherwise specified in D2122.
F1281 − 24
9.1.3 Wall Thickness—Make micrometre measurements of (outer PEX-layer together with the aluminum) are separated
the wall thickness in accordance with Test Method D2122 to mechanically from the inner PEX-layer with an appropriate
determine the maximum and minimum values. Measure the device on the opposite side to the welding seam. The outer
wall thickness at both ends of the pipe to the nearest 0.01 mm layers are separated on one side to about 5 mm from the pipe
(0.0004 in.). in order to allow clamping. The adhesion for the outer
PEX-layer to the aluminum is then visually examined for
9.2 Inner and Outer Crosslinked Polyethylene Layer Thick-
delamination at the corresponding test sample.
nesses:
9.3.2.2 Test Equipment:
9.2.1 Sample Preparation—Cut the pipe with a sharp knife
(1) Tension Testing Device, with suitable pull-off device
or other suitable cutter, ensuring that the pipe after cutting is
(see Fig. 3).
not more than 10 % out-of-round.
(2) D = 95 % of the required pipe inner diameter.
roller
9.2.2 Thickness Determination—Use a hand-held magnify-
(3) d = pipe inner diameter.
i
ing glass equipped with graduated reticule, or a laboratory
9.3.2.3 Test Procedure—Remove the outer layers from the
microscope with graduated reticule. The reticule should mea-
pipe at 23 °C 6 2 °C (73.4 °F 6 3.6 °F) with a linear speed of
sure to the nearest to 0.1 mm (0.004 in.). Determine the
50 mm/min (≈2 in./min). Record the force diagram.
thickness of the inner and outer layers of crosslinked polyeth-
ylene (exclusive of the adhesive layer) at six points around the 9.4 Ring Test:
circumference. One of the points only should be at the 9.4.1 Sample Size and Shape—Cut rings of the PEX-AL-
aluminum weld. PEX pipe so that the two sides are parallel and at 90 6 2° to
the pipe axis. The width of each ring shall be 25 mm 6 1 mm
9.3 Adhesion Tests:
(1 in. 6 0.04 in.). Cut a minimum of 15 samples consecutively
9.3.1 Visual Test:
along the axis of the pipe.
9.3.1.1 Cutting the Spiral—Mount a Stanley 1991 or simi-
9.4.2 Ring Tests—Test the 15 consecutively cut samples
larly sharp but rigid razor-like blade within a protective
using a tensile testing machine. Arrange the rings so that the
housing and angle to cut a 45 6 5° spiral in the pipe (see Fig.
aluminum weld is at 90° to the tensile axis as shown in Fig. 4.
2). Choose a PEX-AL-PEX pipe at random and insert into the
The crosshead speed shall be 50 mm/min 6 2.5 mm/min (2
housing and rotate to form the spiral cut. The cut goes through
in./min 6 0.1 in./min). Mount the rings of pipe on two steel
the complete wall on one side of the pipe only. Run the spiral
rods of minimum diameter of 4 mm (0.16 in.). Record the peak
along the pipe for a minimum distance along the pipe axis
force.
equal to five times the outside diameter.
9.3.1.2 Examining for Delamination—Firmly hold the pipe 9.5 Burst Pressure:
with the spiral cut firm at the uncut end and create a ribbon of 9.5.1 Pipe Sample—Select a length of PEX-AL-PEX pipe at
pipe material by opening out the spiral-cut pipe. Pliers can be random and prepare five consecutive lengths of 300 mm 6 5
used to grip the spiral-cut pipe. Examine the wall of the pipe mm (12 in. 6 0.2 in.). Seal samples at the ends with the
visually side-on for evidence of delamination between the appropriate fittings and test either free- or fixed-end.
metal and plastic layers (see Fig. 1). 9.5.2 Temperature Control—Test samples at a temperature
9.3.2 Separation Test: of 23 °C 6 2 °C (73.4 °F 6 3.6 °F). Contain samples either in
9.3.2.1 Specimen—Five pipe sections of 10 mm (0.394 in.) a temperature controlled water bath or in air (at standard
length are cut at random intervals. The outer layers of the pipe laboratory atmosphere). For samples contained in a water bath,
1 h conditioning is required. For samples tested in air, a 16 h
conditioning period is required.
9.5.3 Burst Pressure—Determine the burst pressure in ac-
cordance with the procedure in Test Method D1599.
FIG. 2 Spiral Cutter for the Delamination Test FIG. 3 Setup for Separation Test
F1281 − 24
evaluation, put pipe in an air-circulating oven at 120 °C
(248 °F) for 20 min. Using a lathe, remove 0.1 mm (0.004 in.)
thick strands from the outside layer, and 0.2 mm (0.008 in.)
thick strands from the inside layer, long enough to obtain a
0.3 g sample for testing. Care should be taken not to cut into
the adhesive layer, as it will effect the test results. (See Note 4.)
9.7.2 Test Method—Test the sample from the inner and outer
surface separately and in accordance with Sections 12 and 13
of Test Methods D2765, Test Method A.
NOTE 4—Including the adhesive in the test specimen will lower the gel
content resulting in a false reading.
10. Quality Assurance
10.1 Quality Assurance—When the product is marked with
this designation, ASTM F1281, the manufacturer affirms that
the product was manufactured, inspected, sampled, and tested
in accordance with this specification and has been found to
FIG. 4 Schematic Presentation of the Pipe Ring Test Showing meet the requirements of this specification. When specified in
the Aluminum Weld at 90° to the Tensile Axis
the purchase order or contract, a report of the test results shall
be furnished.
9.6 Sustained
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F1281 − 23a F1281 − 24 An American National Standard
Standard Specification for
Crosslinked Polyethylene/Aluminum/Crosslinked
Polyethylene (PEX-AL-PEX) Pressure Pipe
This standard is issued under the fixed designation F1281; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This specification covers a coextruded crosslinked polyethylene composite pressure pipe with a welded aluminum tube
reinforcement between the inner and outer layers. The inner and outer crosslinked polyethylene layers are bonded to the aluminum
tube by a melt adhesive. Included is a system of nomenclature for the crosslinked polyethylene-aluminum-crosslinked polyethylene
(PEX-AL-PEX) pipes, the requirements and test methods for materials, the dimensions of the component layers and finished pipe,
adhesion tests, and the burst and sustained pressure performance. Also given are the requirements and methods of marking. The
pipe covered by this specification is intended for use in potable water distribution systems for residential and commercial
applications, water service, building supply lines, underground irrigation systems, and radient panel heating systems, baseboard,
snow- and ice-melt systems, and gases that are compatible with the composite pipe and fittings.
NOTE 1— Piping covered by this specification is not recommended for use in indoor flammable gas applications.
1.2 This specification covers only composite pipes incorporating a welded aluminum tube. Pipes consisting of metallic layers not
welded together are outside the scope of this specification.
1.3 Specifications for connectors for use with pipe meeting the requirements of this specification are given in Annex A1.
1.4 This specification excludes polyethylene-aluminum-polyethylene pipes (see Specification F1282).
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for
information only and are not considered standard.
1.6 The following precautionary caveat pertains only to the test methods portion, Section 9, of this specification: This standard
does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this
standard to establish appropriate safety, health and environmental practices and determine the applicability of regulatory
limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This specification is under the jurisdiction of ASTM Committee F17 on Plastic Piping Systems and is the direct responsibility of Subcommittee F17.11 on Composite.
Current edition approved July 1, 2023Feb. 1, 2024. Published July 2023February 2024. Originally approved in 1990. Last previous edition approved in 2023 as
F1281 – 23.F1281 – 23a. DOI: 10.1520/F1281-23A.10.1520/F1281-24.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1281 − 24
2. Referenced Documents
2.1 ASTM Standards:
D618 Practice for Conditioning Plastics for Testing
D883 Terminology Relating to Plastics
D1598 Test Method for Time-to-Failure of Plastic Pipe Under Constant Internal Pressure
D1599 Test Method for Resistance to Short-Time Hydraulic Pressure of Plastic Pipe, Tubing, and Fittings
D1600 Terminology for Abbreviated Terms Relating to Plastics (Withdrawn 2024)
D1898 Practice for Sampling of Plastics (Withdrawn 1998)
D2122 Test Method for Determining Dimensions of Thermoplastic Pipe and Fittings
D2765 Test Methods for Determination of Gel Content and Swell Ratio of Crosslinked Ethylene Plastics
D3350 Specification for Polyethylene Plastics Pipe and Fittings Materials
E8/E8M Test Methods for Tension Testing of Metallic Materials
F412 Terminology Relating to Plastic Piping Systems
F1282 Specification for Polyethylene/Aluminum/Polyethylene (PE-AL-PE) Composite Pressure Pipe
F1974 Specification for Metal Insert Fittings for Polyethylene/Aluminum/Polyethylene and Crosslinked Polyethylene/
Aluminum/Crosslinked Polyethylene Composite Pressure Pipe
2.2 National Sanitation Foundation Standard:
Standard No. 61 Drinking Water System Components—Health Effects
Standard No. 14 Plastics Piping System Components and Related Materials
2.3 Federal Standard:
Fed. Std. No. 123 Marking for Shipments (Civil Agencies)
2.4 Military Standard:
MIL-STD-129 Marking for Shipment and Storage
2.5 Uniform Classification Committee Standard:
Uniform Freight Classification
2.6 National Motor Freight Traffıc Association Standard:
National Motor Freight Classification
3. Terminology
3.1 Definitions—Definitions are in accordance with Terminology F412, and abbreviations are in accordance with Terminology
D1600, unless otherwise specified.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 assembly—the joint between a fitting and a length of pipe.
3.2.2 PEX-AL-PEX pipe—composite pipe produced by coextrusion or extrusion of layers of polyethylene/aluminum/polyethylene
bonded together with a melt adhesive and crosslinked by irradiation or chemical means in combination heat and moisture.
3.2.3 pipe hoop stress—for simplicity the value of the hoop stress quoted assumes a homogeneous wall. Local values of stress will
vary with the different layers (see 3.2.3.1).
3.2.3.1 Discussion—
Thick walled plastic pipes produced from one material have hoop stresses that vary through the wall, and are usually described
by the Lame Theory. The composite nature of the PEX-AL-PEX pipe, composed of materials with very different Young’s Modulus
values, will, on pressurization, not have a uniform stress distribution through the thickness of the wall of the pipe. The
PEX-AL-PEX pipes have a hoop stress distribution that differs substantially from both the thick and thin walled pipe cases.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Available from NSF International, P.O. Box 130140, 789 N. Dixboro Rd., Ann Arbor, MI 48113-0140, http://www.nsf.org.
Available from DLA Document Services, Building 4/D, 700 Robbins Ave., Philadelphia, PA 19111-5094, http://quicksearch.dla.mil.
Available from the Uniform Classification Committee, Suite 1106, 222 South Riverside Plaza, Chicago, IL 60606.
Available from the National Motor Freight Traffic Association, Inc., National Motor Freight Classification, American Tracking Associations, Inc., Traffic Dept., 1616 P
St., NW, Washington, DC 20036.
F1281 − 24
4. Pipe Classification
4.1 Pipe Diameter—The PEX-AL-PEX pipes are classified by the outside diameter.
4.2 Pipe Dimension Ratio—The concept of dimension ratio is not relevant to PEX-AL-PEX composite pipes, and cannot be used
to relate pressure rating with total wall thickness.
5. Materials
5.1 General—The PEX-AL-PEX pipe is composed of one metallic layer, two layers of polymeric adhesive, and two layers of
crosslinked polyethylene. For pipe made to this specification the constituent materials must meet the following requirements:
5.2 Aluminum—The aluminum shall have a thickness as specified in Table 1. The material shall have minimum elongations and
ultimate tensile strengths of 20 % and 100 MPa (14 600 psi), respectively. The tests shall be conducted according to Test Methods
E8/E8M.
5.3 Crosslinked Polyethylene:
5.3.1 The polyethylene shall be, in the final finished state in the pipe, crosslinked as defined in Terminology D883.
5.3.2 Polyethylene plastics used to make pipe meeting the requirements of this specification shall be virgin resin meeting the
requirements of either Grade PE20A, B, or C; Grade PE23A, B, or C; Grade PE30A, B, or C; or Grade PE33A, B, or C in
accordance with Specification D3350.
5.3.3 Class B compounds shall have sufficient ultraviolet (UV) stabilizers to protect the pipe from deleterious effects due to
continuous outdoor exposure during storage and shipping. Pipe produced from Class B compounds are not suitable for exposed
outdoor application. Class A, B, and C compounds shall have sufficient antioxidants to meet the requirements in Specification
D3350.
5.4 Melt Adhesive—The material shall have a density cell of 1, 2, or 3; a melt index cell of 1, 2, or 3; and a color code of A or
B, in accordance with Specification D3350.
5.5 Rework Material—The use of reclaimed, recycled, or rework plastics is not permitted.
6. Requirements
6.1 General—The requirements and test methods in this specification cover PEX-AL-PEX pipes. Tests on the individual layers
that comprise this composite pipe are outside the scope of this specification. The raw materials used, however, must conform to
the requirements as set out in Section 5.
6.2 Dimensions and Tolerances of Pipe:
TABLE 1 Outside Diameters, Aluminum Thickness, and Tolerances for PEX-AL-PEX
Diameter Nominal
Minimum Outside Tolerance on Minimum, Maximum Out-of- Minimum Aluminum Tolerance on Thickness,
Nominal Pipe Size
A
Diameter, mm (in.) mm (in.) Roundness, mm (in.) Thickness, mm (in.) mm (in.)
(DN) (NPS)
12 ⁄8 12.00 (0.472) +0.30 (0.012) 0.3 (0.012) 0.18 (0.007) +0.09 (+0.0035)
16 ⁄4 16.00 (0.630) +0.30 (0.012) 0.4 (0.016) 0.18 (0.007) +0.15 (+0.006)
20 ⁄8 20.00 (0.787) +0.30 (0.012) 0.5 (0.020) 0.23 (0.009) +0.23 (+0.009)
25 ⁄4 25.00 (0.984) +0.30 (0.012) 0.5 (0.020) 0.23 (0.009) +0.09 (+0.0035)
26 ⁄8 26.00 (1.022) +0.30 (0.012) 0.5 (0.020) 0.53 (0.021) +0.10 (+0.004)
32 1 32.00 (1.260) +0.30 (0.012) 0.5 (0.020) 0.28 (0.011) +0.09 (+0.0035)
40 1 ⁄4 39.95 (1.573) +0.30 (0.012) 0.5 (0.020) 0.33 (0.013) .
50 1 ⁄2 49.90 (1.964) +0.30 (0.012) 0.5 (0.020) 0.47 (0.018) .
63 2 62.90 (2.484) +0.40 (0.016) 0.5 (0.020) 0.57 (0.022) .
75 2 ⁄4 75.10 (2.957) +0.60 (0.024) 1.0 (0.039) 0.67 (0.026) .
A
The out-of-roundness specification applies only to tubing prior to coiling.
F1281 − 24
6.2.1 Pipe Diameter—The minimum outside diameter and tolerances of the pipe shall meet the requirements given in Table 1,
when measured in accordance with 9.1 and 9.1.2. Maximum and minimum (out-of-roundness) tolerances apply only to
measurements made on pipe prior to coiling.
6.2.2 Pipe Wall Thickness—The total pipe wall thickness shall meet the requirements given in Table 2, when measured in
accordance with 9.1 and 9.1.3. The minimum wall thickness at any point of measurement of the pipe shall not be less than the value
specified in Table 2.
6.2.3 Inner and Outer Crosslinked Polyethylene Layer Thicknesses—The thicknesses of the inner and outer layers of crosslinked
polyethylene in the PEX-AL-PEX pipe shall have minimum values and tolerance as specified in Table 2, except for the
polyethylene material in the outer PEX layer overlaying the weld, which shall have a minimum thickness of half those specified
in Table 2. The polyethylene thicknesses shall be measured in accordance with 9.2.
6.2.4 Pipe Length—The pipe shall be supplied coiled or in straight lengths as agreed upon with the purchaser and with an
allowable tolerance of −0 mm (−0 in.).
6.3 Adhesion Test:
6.3.1 For Sizes 0912 ( ⁄8) to 2532 (1) there shall be no delamination of the PEX and AL, either on the bore side or the outside
(see Fig. 1). The test shall be conducted in accordance with 9.3.1.
1 1
6.3.2 The adhesion test of the PEX-layer to the aluminum for Sizes 3240 (1 ⁄4) to 6075 (2 ⁄2) is carried out by a separation test.
The minimum adhesive force is specified in Table 3. The adhesive force shall not fall below these levels. The test shall be
conducted in accordance with 9.3.2.
6.4 Apparent Tensile Strength of Pipe—The pipe rings, when tested in accordance with 9.4, shall meet the minimum strength
specifications defined in Table 4.
6.5 Burst Pressure—The minimum burst pressure for PEX-AL-PEX pipe shall be as given in Table 4, when determined in
accordance with 9.5.
6.6 Sustained Pressure—The PEX-AL-PEX pipe shall not fail, balloon, burst, or weep, as defined in Test Method D1598, when
tested for 10 h at the test at the test pressure given in Table 5 at a temperature of 82 °C (180 °F) in accordance with 9.6.
6.7 Gel Content—When tested in accordance with 9.7, the gel content of the inner and outer tubes of crosslinked polyethylene
shall have minimum values of either 65 % for the fully crosslinked silane material or 60 % for radiation crosslinked polyethylene.
Test Methods D2765 defines gel content (see Note 23).
NOTE 2—The gel test is one of several methods capable of indicating the degree of crosslinking. The different methods for assessing degree of crosslinking
do not necessarily agree, so conformity to this specification requires degree of crosslinking to be determined in accordance with 9.7 only.
TABLE 2 Wall Thickness for PEX-AL-PEX Composite Pipe
Total Wall Wall Outer PEX Inner PEX
Diameter Nominal Nominal Pipe Size
Thickness, min, Tolerance Layer Thickness, Layer Thickness,
(DN) (NPS)
mm (in.) (+) mm (in.) min, mm (in.) min, mm (in.)
12 ⁄8 1.60 (0.063) 0.40 (0.016) 0.40 (0.016) 0.70 (0.028)
16 ⁄4 1.65 (0.065) 0.65 (0.022) 0.40 (0.016) 0.90 (0.035)
20 ⁄8 1.90 (0.075) 0.40 (0.016) 0.40 (0.016) 0.96 (0.038)
25 ⁄4 2.25 (0.089) 0.50 (0.020) 0.40 (0.016) 1.10 (0.043)
26 ⁄8 3.00 (0.118) 0.33 (0.013) 0.40 (0.016) 1.32 (0.052)
32 1 2.90 (0.114) 0.60 (0.024) 0.40 (0.016) 1.34 (0.053)
40 1 ⁄4 3.40 (0.134) 0.60 (0.024) 0.40 (0.016) 1.45 (0.057)
50 1 ⁄2 4.00 (0.157) 0.60 (0.024) 0.40 (0.016) 1.75 (0.069)
63 2 4.60 (0.181) 0.60 (0.024) 0.40 (0.016) 1.75 (0.069)
75 2 ⁄4 7.25 (0.285) 0.60 (0.024) 0.40 (0.016) 2.80 (0.110)
F1281 − 24
NOTE 1—(a) Good pipe showing no delamination, (b) Delamination between the inner layer and the aluminum, and (c) Delamination between the outer
layer and the aluminum.
FIG. 1 Detection of Delamination
TABLE 3 Minimum Adhesive Force for PEX-Al-PEX Composite
Pipe
Minimum Adhesive Force per
Diameter Nominal Nominal Pipe Size
10 mm (0.394 in.) Pipe Strip,
(DN) (NPS)
N (lbf)
40 1 ⁄4 40 (9.0)
50 1 ⁄2 50 (11.2)
63 2 60 (13.5)
75 2 ⁄4 70 (15.7)
TABLE 4 Minimum Pipe Ring Strengths and 23 °C (73.4 °F) Burst
Pressure of PEX-AL-PEX Composite Pipe
Minimum Pipe Minimum Pipe Minimum 23 °C
Diameter
Nominal Pipe Size Ring Strength, Ring Strength, (73.4 °F) Burst
Nominal
(NPS) Type II PE, Type III PE, Pressure, kPa
(DN)
N(lb) N(lb) (psi)
12 ⁄8 2000 (448) 2100 (470) 7000 (1020)
16 ⁄4 2100 (470) 2300 (515) 6000 (880)
20 ⁄8 2400 (538) 2500 (560) 5000 (730)
25 ⁄4 2400 (538) 2500 (560) 4000 (580)
26 ⁄8 2400 (538) 2500 (560) 4000 (580)
32 1 2650 (598) 2500 (560) 4000 (580)
40 1 ⁄4 3200 (719) 3500 (789) 4000 (580)
50 1 ⁄2 3500 (789) 3700 (832) 3800 (554)
63 2 5200 (1169) 5500 (1236) 3800 (554)
75 2 ⁄4 6000 (1349) 6000 (1349) 3800 (554)
F1281 − 24
TABLE 5 Minimum Sustained Pressure for PEX-AL-PEX
Composite Pipe
Diameter Nominal Pipe
Minimum Sustained Pressure PEX-AL-
Nominal Size
PEX, kPa (psi)
(DN) (NPS)
12 ⁄8 2720 (395)
16 ⁄4 2720 (395)
20 ⁄8 2720 (395)
25 ⁄4 2720 (395)
26 ⁄8 2720 (395)
32 1 2720 (395)
40 1 ⁄4 2000 (295)
50 1 ⁄2 2000 (295)
63 2 2000 (295)
75 2 ⁄4 2000 (295)
7. Workmanship
7.1 The pipe shall be free of visible cracks, holes, foreign inclusions, blisters, and other known injurious defects. The pipe shall
be as uniform as practicable in color, opacity, density, and other physical properties.
8. Sampling and Conditioning
8.1 Sampling—Take a sample of the PEX-AL-PEX pipe sufficient to determine conformance with this specification. The number
of specimens designated for each test shall be taken from pipe selected at random in accordance with the random sampling plan
of Practice D1898.
NOTE 3—Sample size and testing frequency of lots for quality control must be established by the manufacturer to ensure conformance to the specification.
Sampling and frequency will vary with the specific circumstances.
8.2 Test Specimens—Not less than 50 % of the test specimens required for any pressure test shall have at least part of the marking
in their central sections. The central section is that portion of the pipe that is at least one pipe diameter away from an end closure.
8.3 Conditioning—Condition the specimens at 23 °C 6 2 °C (73.4 °F 6 3.6 °F) and 50 % 6 5 % relative humidity for not less
than 40 h prior to test in accordance with Procedure A of Practice D618, for those tests where conditioning is required. In cases
of disagreement, the tolerances shall be 61 °C (61.8 °F) and 62 % relative humidity.
8.4 Test Conditions—Conduct the test in the standard laboratory atmosphere of 23 °C 6 2 °C (73.4 °F 6 3.6 °F) and 50 % 6 5 %
relative humidity, unless otherwise specified in the test methods or in this specification. In cases of disagreement, the tolerances
shall be 61 °C (1.8 °F) and 62 % relative humidity.
9. Test Methods
9.1 Dimensions and Tolerances:
9.1.1 Pipe—Any length of the PEX-AL-PEX composite pipe may be used to determine dimensions.
9.1.2 Outside Diameter—Measure the outside diameter of the PEX-AL-PEX pipe in accordance with Test Method D2122.
9.1.3 Wall Thickness—Make micrometre measurements of the wall thickness in accordance with Test Method D2122 to determine
the maximum and minimum values. Measure the wall thickness at both ends of the pipe to the nearest 0.01 mm (0.0004 in.).
9.2 Inner and Outer Crosslinked Polyethylene Layer Thicknesses:
9.2.1 Sample Preparation—Cut the pipe with a sharp knife or other suitable cutter, ensuring that the pipe after cutting is not more
than 10 % out-of-round.
9.2.2 Thickness Determination—Use a hand-held magnifying glass equipped with graduated reticule, or a laboratory microscope
F1281 − 24
with graduated reticule. The reticule should measure to the nearest to 0.1 mm (0.004 in.). Determine the thickness of the inner and
outer layers of crosslinked polyethylene (exclusive of the adhesive layer) at six points around the circumference. One of the points
only should be at the aluminum weld.
9.3 Adhesion Tests:
9.3.1 Visual Test:
9.3.1.1 Cutting the Spiral—Mount a Stanley 1991 or similarly sharp but rigid razor-like blade within a protective housing and
angle to cut a 45 6 5° spiral in the pipe (see Fig. 2). Choose a PEX-AL-PEX pipe at random and insert into the housing and rotate
to form the spiral cut. The cut goes through the complete wall on one side of the pipe only. Run the spiral along the pipe for a
minimum distance along the pipe axis equal to five times the outside diameter.
9.3.1.2 Examining for Delamination—Firmly hold the pipe with the spiral cut firm at the uncut end and create a ribbon of pipe
material by opening out the spiral-cut pipe. Pliers can be used to grip the spiral-cut pipe. Examine the wall of the pipe visually
side-on for evidence of delamination between the metal and plastic layers (see Fig. 1).
9.3.2 Separation Test:
9.3.2.1 Specimen—Five pipe sections of 10 mm (0.394 in.) length are cut at random intervals. The outer layers of the pipe (outer
PEX-layer together with the aluminum) are separated mechanically from the inner PEX-layer with an appropriate device on the
opposite side to the welding seam. The outer layers are separated on one side to about 5 mm from the pipe in order to allow
clamping. The adhesion for the outer PEX-layer to the aluminum is then visually examined for delamination at the corresponding
test sample.
9.3.2.2 Test Equipment:
(1) Tension Testing Device, with suitable pull-off device (see Fig. 3).
(2) D = 95 % of the required pipe inner diameter.
roller
(3) d = pipe inner diameter.
i
9.3.2.3 Test Procedure—Remove the outer layers from the pipe at 23 °C 6 2 °C (73.4 °F 6 3.6 °F) with a linear speed of 50
mm/min (≈2 in./min). Record the force diagram.
9.4 Ring Test:
FIG. 2 Spiral Cutter for the Delamination Test
F1281 − 24
FIG. 3 Setup for Separation Test
9.4.1 Sample Size and Shape—Cut rings of the PEX-AL-PEX pipe so that the two sides are parallel and at 90 6 2° to the pipe
axis. The width of each ring shall be 25 mm 6 1 mm (1 in. 6 0.04 in.). Cut a minimum of 15 samples consecutively along the
axis of the pipe.
9.4.2 Ring Tests—Test the 15 consecutively cut samples using a tensile testing machine. Arrange the rings so that the aluminum
weld is at 90° to the tensile axis as shown in Fig. 4. The crosshead speed shall be 50 mm/min 6 2.5 mm/min (2 in./min 6 0.1
in./min). Mount the rings of pipe on two steel rods of minimum diameter of 4 mm (0.16 in.). Record the peak force.
9.5 Burst Pressure:
9.5.1 Pipe Sample—Select a length of PEX-AL-PEX pipe at random and prepare five consecutive lengths of 300 mm 6 5 mm
(12 in. 6 0.2 in.). Seal samples at the ends with the appropriate fittings and test either free- or fixed-end.
9.5.2 Temperature Control—Test samples at a temperature of 23 °C 6 2 °C (73.4 °F 6 3.6 °F). Contain samples either in a
temperature controlled water bath or in air (at standard laboratory atmosphere). For samples contained in a water bath, 1 h
conditioning is required. For samples tested in air, a 16 h conditioning period is required.
9.5.3 Burst Pressure—Determine the burst pressure in accordance with the procedure in Test Method D1599.
9.6 Sustained Pressure Test:
FIG. 4 Schematic Presentation of the Pipe Ring Test Showing the Aluminum Weld at 90° to the Tensile Axis
F1281 − 24
9.6.1 Samples—Each test sample of PEX-AL-PEX pipe shall have a minimum length between end closures of at least ten times
the average outside diameter, but not less than 250 mm (10 in.). Seal specimens at both ends with the appropriate fittings and fill
the samples for testing with water.
9.6.2 Test Procedures—Test the samples in a temperature controlled water bath or in air, in accordance with Test Method D1598.
A test temperature of 82 °C 6 2 °C (180 °F 6 3.6 °F) is specified. For each pipe size test six samples. For testing in a water bath,
condition the test samples for at least 2 h in the water bath at the test temperature prior to pressurization For testing in air, condition
the samples for at least 4 h in air at the test temperature prior to pressurization. Maintain the pressure at the pressure given in Table
5 for the duration of the test.
9.6.3 Failure—Any continuous loss of pressure of the test sample shall constitute failure of the test. Failure of one of the six is
caus
...