prEN 1488

• Abstract:

  This document specifies, dimensions, materials and performance requirements (including methods of test) for expansion groups, of nominal sizes from DN 15 to DN 25, having working pressures from 0,1 MPa (1 bar) to 1,0 MPa (10 bar).; Expansion groups are fitted to the cold potable water supply only for expansion purposes, e.g. of storage water heaters, having a maximum distribution temperature of 95 °C.; Expansion groups limit pressure in the water heater to which they are fitted, that is produced by thermal expansion of the water, prevent the backflow of water into the supply pipe and prevent the discharged water to get into contact with the water in the water heater.; Expansion groups do not control temperature and alone do not constitute the protection required for storage water heaters.; NOTE The use of the device specified in this document does not override the need to use controls (e.g. thermostats and thermal cut-outs) which act directly on the power sources of water heaters (for more information see Annex A).

• Status: Not Published
• Publication Date: 19-Jul-2027
• ICS: 91.140.60 - Water supply systems
• Technical Committee: CEN/TC 164 - Water supply
• Drafting Committee: CEN/TC 164/WG 14 - Valves and fitting for buildings and devices to prevent pollution by backflow
• Current Stage: 4020 - Submission to enquiry - Enquiry
• Start Date: 10-Sep-2026
• Due Date: 07-Apr-2026
• Completion Date: 10-Sep-2026
• Directive: 98/83/EC - Quality of water intended for human consumption
• Ref Project: oSIST prEN 1488:2026 - Building valves - Expansion groups - Tests and requirements

• Referred By: EN ISO 15614-9:2025 - Specification and qualification of welding procedures for metallic materials - Welding procedure test - Part 9: Underwater hyperbaric wet welding (ISO 15614-9:2025)
• Effective Date: 28-Jan-2026
• Referred By: EN ISO 11970:2025 - Specification and qualification of welding procedures for production welding of steel and nickel-base castings (ISO 11970:2025)
• Effective Date: 28-Jan-2026
• Referred By: EN 14025:2023 - Tanks for the transport of dangerous goods - Metallic pressure tanks - Design and construction
• Effective Date: 28-Jan-2026
• Revises: EN 1488:2021 - Building valves - Expansion groups - Tests and requirements
• Effective Date: 18-Dec-2024

prEN 1488 is a CEN draft European Standard for building valves called expansion groups. It specifies dimensions, materials, performance requirements and test methods for DN 15 to DN 25 devices used on the cold potable water supply of storage water heaters with a maximum distribution temperature of 95 °C. It is written for manufacturers, test laboratories, specifiers, quality teams and buyers who need to design, test, mark or select these devices.

What does prEN 1488 specify?

prEN 1488 sets the technical requirements for expansion groups that limit pressure rise from thermal expansion, prevent backflow into the supply pipe and keep discharged water separate from the water in the heater. It also makes clear that an expansion group does not control temperature and is not, by itself, the full protection required for storage water heaters.

The document is organized into 15 clauses covering scope, references, terms, materials, disinfection compatibility, design and dimensions, test apparatus, hydraulic tests, mechanical tests, component tests, acoustic tests, classification, designation, marking, and technical documents. It also has three informative annexes.

Annex	What it covers
Annex A	Test sequences for the different samples and clauses
Annex B	Classification of water heaters according to heating method
Annex C	Disinfection of the test rig

What are the key requirements of prEN 1488?

Materials and disinfection resistance

prEN 1488 requires the materials of the device to be corrosion resistant or protected against corrosion, and to avoid harmful interaction between different materials. Where dezincification-resistant materials are required in a country, brass materials must be verified to EN ISO 6509-1 and identified with DR where applicable.

The chapter on materials also covers coating, residual stress and corrosion testing. This matters in practice because the device must keep its function after exposure to water, cleaning, and long-term service conditions.

Clause 5 adds disinfection compatibility. The device must remain functional after shock disinfection testing using one of the listed disinfectant solutions. In practical terms, the product has to survive maintenance disinfection in drinking water installations without losing its performance.

Design and dimensional features

Clause 6 requires the expansion valve spring to be isolated from the water by a diaphragm or equivalent, and the moving parts must be designed to avoid seizure or sticking. The setting parts must not be reachable by the end user without damage, and the normal operation must not be altered by external forces.

The device body must provide flats for a spanner, and the expansion valve must have an easing gear for periodic functional checks. The document also sets rules for the test port, pressure measuring port, discharge connection to drain, replacement of a removable expansion valve, and the use of a check valve complying with EN 13959. For users, this affects installation, maintenance access and whether parts can be replaced without changing performance.

Hydraulic, mechanical and component performance

Clause 8 sets the hydraulic checks. The device is tested for minimum flow rate, and for tightness of the isolating valve and of the complete expansion group. No leakage is allowed in these tests, so the product has to seal reliably before it reaches service.

Clauses 9 and 10 cover mechanical strength and component endurance. These include pressure strength of the body, bending resistance, torsional strength, torque resistance of captive nuts or tail pieces, manual operation and endurance of the isolating valve, and check valve tightness at low and high pressure. The expansion valve itself is checked for opening, closing and discharge behavior, then cycled for endurance. In practice, these tests show whether the group can be installed, operated and maintained without damage or loss of function.

Acoustic classification, designation, marking and delivery

Clause 11 classifies the device by noise emission into acoustic groups at 0.3 MPa using EN ISO 3822-1 and EN ISO 3822-3. Clause 12 limits the use of each nominal size by heater inlet dimensions, heating power and water heater volume.

Clause 13 defines the designation using nominal size, nominal set pressure, acoustic group and EN 1488. Clause 14 requires permanent marking with the manufacturer identification, model or series, nominal size, nominal set pressure, flow direction, manufacture date or code, acoustic classification and, where applicable, DR. Clause 15 requires delivery information and installation instructions, including operating conditions, maintenance, spare parts and material information.

What terms does prEN 1488 define?

• Expansion group - A single unit that limits pressure rise from water heating, prevents backflow and contamination, and includes the main functional components in the order given by the standard.
• Isolating valve - The valve that separates the water heater from the potable water supply for maintenance or isolation.
• Check valve - The valve that lets water enter the heater but stops it returning to the water supply.
• Expansion valve - The valve that limits heater pressure by discharging water to drain.
• Air break to drain - The vertical separation or open break that keeps discharged water from reconnecting to the drain system.
• Pressure measuring port - The port used to connect pressure-measuring equipment.
• Nominal set pressure (Pnr) - The pressure set during production for the expansion valve.
• Water tightness pressure (Pe) - The pressure up to which the expansion valve remains closed.
• Opening pressure (Po) - The pressure at which the valve opens and water appears at the outlet.
• Rating pressure (Pdn) - The pressure at which the discharge flow rises above the specified limit.
• Closing pressure (Pf) - The pressure at which the valve closes again after reaching rating flow.

Who uses prEN 1488?

Manufacturers use prEN 1488 to design expansion groups, choose materials, set the nominal set pressure, and prepare product marking and installation instructions. Test laboratories use it for flow, leak tightness, mechanical strength, endurance, acoustic and disinfection testing.

Quality managers, certifiers and buyers use it to define acceptance criteria for potable-water devices. Installers and system designers use it when selecting devices for storage water heaters, backflow protection and service isolation in building water systems.

What changed in prEN 1488 from the previous edition?

prEN 1488 states that it will supersede EN 1488:2021. It also lists these technical changes compared with that edition:

• the materials chapter was completely revised
• disinfection testing was introduced
• the torque test was added
• testing for the safety valve was changed and optimized
• the coating test procedure was revised
• normative references were updated
• editorial changes were made throughout the document

Which standards are used with prEN 1488?

Standard	What it contributes
EN 806 (all parts)	Installation rules for water intended for human consumption inside buildings
EN 1254-2	Compression fittings for copper tubes
EN 1717	Backflow protection and discharge-to-drain requirements
EN 10226-1	Taper external and parallel internal pipe threads
EN 13959	Check valve functional requirements
EN ISO 228-1	Pipe threads not sealed on the threads
EN ISO 3822-1 and EN ISO 3822-3	Acoustic test method and mounting/operating conditions
EN ISO 9227	Salt-spray corrosion testing
EN ISO 6509-1	Dezincification resistance test for copper alloys with zinc
ISO 6957	Ammonia test for stress corrosion resistance
EN 1487, EN 1489, EN 1490, EN 1491, EN 1567, EN 13828, EN 14597	Related safety and control standards named for system selection in Annex B and the bibliography

What does the prEN 1488 document contain?

prEN 1488 contains tables for flow rates, discharge flow rates, torques, dimensions, acoustic groups and product classification. It also includes detailed test procedures for pressure, leakage, bending, torsion, endurance, disinfection and corrosion resistance.

The document uses a pressure diagram to define key valve pressures, an example for discharge behavior, and an example test rig for disinfection. Annex A then arranges the tests into sample sequences, so laboratories can see which specimens are used for each check.

SLOVENSKI STANDARD
01-november-2026
Ventili v stavbah - Ekspanzijski bloki - Preskusi in zahteve
Building valves - Expansion groups - Tests and requirements
Gebäudearmaturen - Sicherheitsgruppen für Expansionswasser - Prüfungen und
Anforderungen
Robinetterie de bâtiment - Groupes d'expansion - Essais et exigences
Ta slovenski standard je istoveten z: prEN 1488
ICS:
23.060.01 Ventili na splošno Valves in general
91.140.60 Sistemi za oskrbo z vodo Water supply systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2026
ICS 91.140.60 Will supersede EN 1488:2021
English Version
Building valves - Expansion groups - Tests and
requirements
Robinetterie de bâtiment - Groupes d'expansion - Gebäudearmaturen - Sicherheitsgruppen für
Essais et exigences Expansionswasser - Prüfungen und Anforderungen
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 164.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1488:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Materials . 9
4.1 General. 9
4.2 Dezincification resistant copper alloy . 9
4.3 Surface coating . 9
4.4 Corrosion . 9
4.4.1 General. 9
4.4.2 Corrosion resistance test . 10
4.5 Detection of residual stress . 10
4.5.1 General. 10
4.5.2 Principle . 10
4.5.3 Procedure . 10
4.5.4 Requirements . 11
5 Compatibility of the expansion group with disinfection . 11
5.1 General. 11
5.2 Requirements . 11
5.3 Procedure . 11
6 Design and dimensional characteristics . 12
6.1 General. 12
6.2 Dimensional characteristics . 12
6.3 Test port and pressure measuring port. 12
6.4 Expansion valve outlet connection to air break to drain . 13
6.5 Expansion valve discharge connection to drain device . 13
6.6 Connections . 13
6.7 Replacing of the expansion valve . 13
6.8 Check valve . 13
7 Apparatus . 14
7.1 General. 14
7.2 Tolerances of parameters and accuracy of measure instruments . 14
7.2.1 Tolerances on set parameters . 14
7.2.2 Accuracy of measuring instruments . 14
7.2.3 Test media . 14
8 Hydraulic tests . 14
8.1 Flow rate test . 14
8.1.1 Procedure . 14
8.1.2 Requirements . 14
8.2 Tightness test . 15
8.2.1 General. 15
8.2.2 Tightness test for the isolating valve at a pressure of 1,6 MPa (16 bar) . 15
8.2.3 Tightness test for the expansion group . 15
9 Mechanical tests . 15
9.1 Mechanical strength tests . 15
9.1.1 Pressure test of the body of the expansion group . 15
9.1.2 Bending moment test . 16
9.2 Mechanical strength test of the operating control of the expansion valve . 16
9.2.1 Procedure . 16
9.2.2 Requirements . 17
9.3 Torsional strength test of the expansion group’s body . 17
9.3.1 General . 17
9.3.2 Procedure . 17
9.3.3 Requirements . 17
9.4 Torque test of the captive rotating nuts/tail pieces . 17
9.4.1 General . 17
9.4.2 Procedure . 17
9.4.3 Requirements . 18
10 Expansion group component tests . 18
10.1 Isolating valve . 18
10.1.1 General . 18
10.1.2 Manual operation test . 18
10.1.3 Endurance test . 19
10.2 Tightness between check valve and group’s body . 19
10.2.1 General . 19
10.2.2 Leak tightness between the group’s body and the check valve at low pressure . 19
10.2.3 Leak tightness between the group’s body and the check valve under high pressure. 19
10.3 Expansion valve . 19
10.3.1 Pressures . 19
10.3.2 Cold water pressure tests . 20
10.3.3 Repeat tests . 21
10.4 Endurance test . 21
10.4.1 Procedure . 21
10.4.2 Requirements . 22
10.5 Operating control tests . 22
10.5.1 Operation test . 22
10.5.2 Endurance test . 22
10.6 Air break to drain . 22
11 Acoustic tests . 22
12 Classification . 23
13 Designation . 23
14 Marking . 23
15 Technical documents and presentation at delivery . 24
Annex A (informative) Test sequences . 26
Annex B (informative) Classification of water heaters according to heating method . 28
Annex C (informative) Disinfection of test rig . 30
Bibliography . 31

European foreword
This document (prEN 1488:2026) has been prepared by Technical Committee CEN/TC 164 “Water
supply”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 1488:2021.
— chapter on materials was completely revised;
— testing with disinfectant was introduced;
— torque test was added;
— testing for safety valve was changed and optimized;
— coating test procedure was revised;
— normative references were updated;
— editorial changes have been made throughout the entire document.
Introduction
With regards to potential adverse effect on the quality of water intended for human consumption, caused
by the product covered by this document:
a) This document provides no information as to whether the product may be used without restriction
in any of the Member States of the EU or EFTA.
b) It should be noted that, whilst awaiting the adoption of verifiable European criteria, existing national
regulations concerning the use or the characteristics of this product remain in force.
1 Scope
This document specifies, dimensions, materials and performance requirements (including methods of
test) for expansion groups, of nominal sizes from DN 15 to DN 25, having working pressures from
0,1 MPa (1 bar) to 1,0 MPa (10 bar).
Expansion groups are fitted to the cold potable water supply only for expansion purposes, e.g. of storage
water heaters, having a maximum distribution temperature of 95 °C.
Expansion groups limit pressure in the water heater to which they are fitted, that is produced by thermal
expansion of the water, prevent the backflow of water into the supply pipe and prevent the discharged
water to get into contact with the water in the water heater.
Expansion groups do not control temperature and alone do not constitute the protection required for
storage water heaters.
NOTE The use of the device specified in this document does not override the need to use controls (e.g.
thermostats and thermal cut-outs) which act directly on the power sources of water heaters (for more information
see Annex A).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 806 (all parts), Specifications for installations inside buildings conveying water for human consumption
EN 1254-2, Copper and copper alloys - Plumbing fittings - Part 2: Compression fittings for use with copper
tubes
EN 1717, Protection against pollution of water intended for human consumption in potable water
installations and general requirements for devices to prevent pollution by backflow
EN 10226-1, Pipe threads where pressure tight joints are made on the threads - Part 1: Taper external
threads and parallel internal threads - Dimensions, tolerances and designation
EN 13959, Anti-pollution check valves - DN 6 to DN 250 inclusive family E, type A, B, C and D
EN ISO 228-1, Pipe threads where pressure-tight joints are not made on the threads - Part 1: Dimensions,
tolerances and designation (ISO 228-1)
EN ISO 3822-1, Acoustics - Laboratory tests on noise emission from appliances and equipment used in water
supply installations - Part 1: Method of measurement (ISO 3822-1:1999)
EN ISO 3822-3, Acoustics - Laboratory tests on noise emission from appliances and equipment used in water
supply installations - Part 3: Mounting and operating conditions for in-line valves and appliances (ISO 3822-
3:2018)
EN ISO 9227, Corrosion tests in artificial atmospheres - Salt spray tests (ISO 9227)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

All pressures are gauge unless otherwise stated.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
expansion group
group that limits the pressure increase due to the volume expansion when water is heated, prevents the
backflow of the water into the main circuit and the contamination of water contained in the water heater
with discharged water, allows to control the function of the backflow prevention and isolates the water
heater for maintenance services
Note 1 to entry: An expansion group comprises of the following components in a single unit, in an upstream to
downstream order as shown in Table 1.
Note 2 to entry: For the purpose of this standard the expansion group is hereafter referred as the “device”.
Table 1 — Components of the expansion group
Component Quantity
an isolating valve 1
a test port for monitoring the check valve 1
a check valve 1
a
an isolating valve 1
a
an additional outlet connection 1
an expansion valve 1
an air break to drain 1
a
a pressure measuring port 1
a
Optional
3.2
isolating valve
valve that isolates the water heater from the potable water supply
3.3
check valve
valve that allows water to flow into a water heater, and automatically prevents water returning to the
water supply
3.4
additional outlet connection
connection to supply cold potable water to be supplied to an additional device, e.g. inline hot water supply
tempering valves, etc
3.5
expansion valve
valve that limits the pressure of the water in the water heater to a predetermined value by discharging
water to drain
3.6
air break to drain
vertical distance realised by air inlets or full disconnection between the lowest point of the outlet and
spill over level of the atmospheric over flow
3.7
pressure measuring port
measuring port that allows pressure measuring equipment to be connected
3.8
nominal set pressure
P
nr
pressure of the expansion valve which is set on production
Note 1 to entry: The “nominal set pressure” (P ) is often called “set pressure”.
nr
3.9
water tightness pressure
P
e
pressure up to which the expansion valve is closed
Note 1 to entry: See Figure 1.
3.10
initial opening pressure
P
dc
pressure at which the expansion valve opens for the first time, as indicated by the first droplet of water
at the outlet of the expansion group, after a period of storage
Note 1 to entry: See Figure 1.
3.11
opening pressure
P
o
pressure at which the expansion valve open as indicated by the appearance of water at the outlet of the
expansion group
Note 1 to entry: See Figure 1.
3.12
rating pressure
Pdn
pressure at which the discharged flow is above the limit
Note 1 to entry: See Figure 1 and Table 8.
3.13
closing pressure
P
f
pressure at which the expansion valve closes after having reached the rating pressure
Note 1 to entry: See Figure 1.
Key
Y pressure
X time
Figure 1 — Pressures
4 Materials
4.1 General
NOTE Health and quality requirements in accordance with European and national legislation for final materials
in contact with water intended for human consumption are not covered by this document.
4.2 Dezincification resistant copper alloy
Copper-zinc alloys containing more than 15 % zinc are subject to dezincification when submitted to
water capable of dezincification. In the countries where the use of products made of dezincification
resistant materials is required, the materials used shall guarantee a dezincification depth less than
200 μm in any direction. For this purpose, materials shall be tested in accordance with EN ISO 6509-1
and the product shall be marked in compliance with the indications according to Clause 14.
4.3 Surface coating
The outside and inside surfaces of the device can contain a coating. Such coating shall not impair the
functional characteristics of the device.
Only for materials with inadequate corrosion resistance (e.g. iron steel) the corrosion resistance test in
4.4.2 shall be determined.
4.4 Corrosion
4.4.1 General
The applied materials shall be corrosion resistant or protected against corrosion. The materials used shall
not have an adverse effect on each other.
Only for materials with inadequate corrosion resistance (e.g. iron steel) the corrosion resistance test in
4.4.2 shall be determined.
4.4.2 Corrosion resistance test
4.4.2.1 General
The purpose of the corrosion resistance test is to qualify all used materials of the external part of the
product. The whole device shall be tested, not only the parts in contact with potable water.
4.4.2.2 Procedure
Samples shall be prepared for the corrosion resistance test as described as follows.
Carry out the test in accordance with the neutral saline-spray test of EN ISO 9227 and the following:
a) Subject the device to spraying for at least 100 h, interrupt the spraying treatment for (48 ± 1) h while
maintaining the heat in the tank and resume the spraying treatment for another (100 ± 1) h.
b) For the duration of the tests, the tank should only be opened to check and maintain the conditions,
the maximum rest period in spraying being 30 min per day. The heating should not be interrupted;
samples under test should not be handled, washed or checked.
c) After treatment and before visual examination, rinse the test samples in water to remove any salt
residue.
4.4.2.3 Requirements
The device shall comply with the requirements as included in cold water pressure test (10.3.2). The
results shall not deviate by more than 10 % from the original values.
4.5 Detection of residual stress
4.5.1 General
This test shall be performed for devices which have bodies made out of brass materials and with female
threads according to EN 10226-1 and compression ends according to EN 1254-2.
4.5.2 Principle
This test is based on ISO 6957. Its purpose is to verify the resistance to cracking under stress corrosion
in ammonia medium (as described in 4.5.3 b)).
The test entails exposing test specimens consisting of the assembled device in an atmosphere loaded with
ammonia vapour.
4.5.3 Procedure
This subclause integrates elements of ISO 6957.
Test solution:
a) Use solutions of analysis quality and of distilled water.
b) Solution of ammonia at 20 % (in weight).
c) The pH of the test solution is to be adjusted to 9,5 by using hydrochloric acid.
d) The test temperature is to be (23 ± 2) °C with a measurement uncertainty of ± 1 °C.
Test specimen:
a) The test specimen consists of three samples of a single assembled product. The test specimen is
inserted into the test enclosure under no stress.
Instructions:
a) Rinse the test specimens with a clean non-chlorinated solvent (for example, ethanol).
b) Let it dry in the air.
c) Insert the test specimens into the test enclosure along with the ammonia solution. The volume of the
container made of glass (e.g. desiccator) is to be minimum (10 ± 1) l.
d) The volume of the solution inserted is to be (200 ± 10) ml per 3 l of total volume of the container (e.g.
for a 10 l container it means (667 ± 33) ml.
e) Place the test specimens in the container in such a way that they will not touch each other and that
they will not be in contact with the solution.
+2
f) After an exposure of ( 24 ) h, remove the test specimens and rinse them.
4.5.4 Requirements
After the test, the body of the device shall be inspected visually for stress corrosion cracking. No cracking
shall occur.
At least two samples shall be in accordance with the test in 10.3.2.
5 Compatibility of the expansion group with disinfection
5.1 General
The disinfection test is carried out to ensure that a device can continue to fulfil its function after several
curative disinfection measures (shock disinfection) in a drinking water installation (see Table 2).
NOTE See Annex C.
5.2 Requirements
The entire device shall remain functional after carrying out the disinfection test with one of the three
disinfectant solutions (Table 2).
The device shall comply with th
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