ISO 9853:2026

• Abstract:

  This document specifies a test method to determine if a fitting will fail in crushing mode under compression before a predefined percentage deformation of moulded fittings for thermoplastics piping systems and provides recommended percentage deformation for fittings (see Annex A). This document applies to fittings made from unplasticized poly(vinyl chloride) (PVC-U), high-impact poly(vinyl chloride) (PVC-HI), chlorinated poly(vinyl chloride) (PVC-C), polyethylene (PE), polypropylene (PP), acrylonitrile-butadiene-styrene (ABS), poly(vinylidene difluoride) (PVDF), poly(phenyl sulfone) (PPSU) and unplasticized polyamide (PA-U). This document can also be applied to moulded fittings made from other thermoplastics, in which case the test conditions can differ.

• Status: Published
• Publication Date: 17-Sep-2026
• ICS: 23.040.45 - Plastics fittings
• Technical Committee: ISO/TC 138/SC 5 - General properties of pipes, fittings and valves of plastic materials and their accessories -- Test methods and basic specifications
• Drafting Committee: ISO/TC 138/SC 5/WG 22 - Thermoplastics pipes for the transport of fluids
• Current Stage: 6060 - International Standard published
• Start Date: 18-Sep-2026
• Due Date: 03-May-2027
• Completion Date: 18-Sep-2026

• Revises: ISO 9853:1991 - Injection-moulded unplasticized poly(vinyl chloride) (PVC-U) fittings for pressure pipe systems — Crushing test
• Effective Date: 04-May-2024

ISO 9853:2026 is an International Standard published by ISO for thermoplastics piping systems. It specifies a crushing test for moulded fittings to check whether a fitting fractures under compression before a defined percentage deformation is reached, and Annex A gives the recommended deformation criteria for the listed material families. The document is used by manufacturers, laboratories and other parties that need a repeatable check on moulded fittings made from the covered thermoplastics.

What does ISO 9853:2026 specify?

ISO 9853:2026 covers a laboratory method for checking the crushing behaviour of moulded fittings under compression. It applies to fittings made from PVC-U, PVC-HI, PVC-C, PE, PP, ABS, PVDF, PPSU and PA-U, and it can also be applied to moulded fittings made from other thermoplastics when the test conditions are adjusted.

The document is organized into Clauses 1 to 9, followed by Annex A and a bibliography. Clauses 1 to 9 cover scope, normative references, terms and definitions, principle, apparatus, test pieces, conditioning, procedure and test report.

Annex	What it covers
A	Informative recommended percentage deformation for fittings, used with the pass/fail assessment in Clause 8.

What are the key requirements of ISO 9853:2026?

ISO 9853:2026 sets out a controlled compression test and then defines how to judge the fitting after loading. The main practical point is that the test is not just about applying force - it also controls specimen preparation, temperature, loading speed, orientation and reporting so that results can be compared.

• Clause 4 - Principle: place the fitting between parallel plates and compress it at a controlled rate until it fails or reaches the target deformation. In practice, the examiner looks for cracking, delamination or fracture along the weld line.
• Clause 5 - Apparatus: use a compression testing machine that complies with ISO 5893, rigid and smooth plates, any supports needed for grooved fittings, and measuring devices for plate spacing and force. In practice, the equipment must not flex or distort the test.
• Clause 6 - Test pieces: test fittings in the as-manufactured condition, remove rubber sealing rings before testing, and use enough specimens to represent the batch. In practice, the sample must reflect the product as supplied, not a modified assembly.
• Clause 7 - Conditioning: condition the test pieces at the specified room temperature for a time that depends on wall thickness. In practice, thicker fittings need longer stabilization before the test.
• Clause 8 - Procedure: measure the fitting dimensions, position the fitting correctly on the plates, and control the weld line position where relevant. In practice, the orientation of sockets, caps and reducers affects the result.
• Clause 8 - Loading rate and stop condition: use the compression speed specified for the material family, and stop when failure occurs or when the deformation level from Annex A is reached. For PE, PP and PA-U, the test stops when the inner surface touches or any failure occurs, whichever comes first.
• Annex A - Acceptance guidance: Annex A gives the recommended deformation level for the material families covered by the standard. In practice, this is the reference used to decide whether a fitting has passed for the listed materials.
• Clause 9 - Test report: record the sample identity, material, size, socket type, number of pieces tested, conditioning, supports used, weld line position, force if required, deformation values, result, deviations and date. In practice, the report provides the traceability needed for quality control or product assessment.

What terms does ISO 9853:2026 define?

• Percentage deformation - the change in fitting diameter relative to the initial diameter, determined from the crushing test.
• Moulded fittings - fittings tested in the as-manufactured condition, before any transformation or solvent jointing.
• Residual stresses - internal stresses left from moulding that can make a fitting fail under crushing load.
• Weld line - the line in some fittings whose position must be controlled during the test.
• PVC-U - unplasticized poly(vinyl chloride), one of the thermoplastics covered by the method.
• PE - polyethylene, a covered material family with a specific stop condition in the procedure.
• PP - polypropylene, another covered material family with the same general stop condition as PE.
• PVDF - poly(vinylidene difluoride), one of the listed fitting materials.

Who uses ISO 9853:2026?

ISO 9853:2026 is used by manufacturers of thermoplastics piping fittings, test laboratories, and quality or product certification teams that need to assess crush resistance and internal stress in moulded parts. It is also relevant to specifiers and buyers writing product requirements for thermoplastics piping systems, because the test procedure and report items define how results are generated and compared.

What changed in ISO 9853:2026 from the previous edition?

ISO 9853:2026 is the second edition and it replaces ISO 9853:1991. The changes stated in the document are:

• the title was revised;
• the scope was expanded with PVC-HI, PVC-C, PE, PP, ABS, PVDF, PPSU and PA-U;
• Clause 2 on normative references was added;
• the test parameters were modified to cover the added materials;
• the apparatus requirements were detailed.

Which standards are used with ISO 9853:2026?

• ISO 3126 - used for determining the dimensions of the plastics components before testing.
• ISO 5893 - sets the requirements for the compression testing machine used in the apparatus clause.

The bibliography also cites related standards for PVC-U fittings and valves, ABS/PVC-U/PVC-C component specifications, and preparation of tubular test pieces for hydrostatic strength work.

What does the ISO 9853:2026 document contain?

ISO 9853:2026 contains the test principle, apparatus requirements, specimen preparation, conditioning and the step-by-step crushing procedure. It also includes a conditioning-time table, a material-dependent compression-speed table, and formulas for calculating percentage deformation and the plate spacing used to stop the test. Clause 9 lists the reporting items needed to document the result, and Annex A gives the recommended deformation guidance for judging the fittings.

International
Standard
ISO 9853
Second edition
Thermoplastics piping systems —
2026-09
Crushing test for moulded fittings
Systèmes de canalisations en matières thermoplastiques — Essai
à l'écrasement pour les raccords moulés
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
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or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: [phone]
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Test pieces . 2
7 Conditioning . 2
8 Procedure . 3
9 Test report . 4
Annex A (informative) Recommended percentage deformation for fittings . 5
Bibliography . 6

iii
Foreword
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Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the
transport of fluids, Subcommittee SC 5, General properties of pipes, fittings and valves of plastic materials and
their accessories — Test methods and basic specifications.
This second edition cancels and replaces the first edition (ISO 9853:1991), which has been technically
revised.
The main changes are as follows:
— the title has been revised;
— in the Scope, the following materials have been added: PVC- HI, PVC-C, PE, PP, ABS, PVDF, PPSU and PA-U;
— Clause 2 on normative references have been added;
— the test parameters have been modified due to the addition of different materials;
— the requirements of test apparatus have been detailed.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Moulded fittings for thermoplastics piping systems can be crushed without their failing if they contain no
residual stresses as a result of the moulding process. However, if these residual stresses are excessively
high, the fitting will fail when a crushing force is applied.
The percentage deformation of a fitting, in relation to its initial diameter, constitutes a simple criterion for
the selection of fittings having an acceptable level of internal stress.
Meanwhile, when fittings are the initial moulds from injection moulding process, some potential defects
might also exist in these fittings. A crushing test can provide an effective acceptable level of internal stress
for fittings.
v
International Standard ISO 9853:2026(en)
Thermoplastics piping systems — Crushing test for moulded
fittings
1 Scope
This document specifies a test method to determine if a fitting will fail in crushing mode under compression
before a predefined percentage deformation of moulded fittings for thermoplastics piping systems and
provides recommended percentage deformation for fittings (see Annex A).
This document applies to fittings made from unplasticized poly(vinyl chloride) (PVC-U), high-impact
poly(vinyl chloride) (PVC-HI), chlorinated poly(vinyl chloride) (PVC-C), polyethylene (PE), polypropylene
(PP), acrylonitrile-butadiene-styrene (ABS), poly(vinylidene difluoride) (PVDF), poly(phenyl sulfone)
(PPSU) and unplasticized polyamide (PA-U).
This document can also be applied to moulded fittings made from other thermoplastics, in which case the
test conditions can differ.
2 Normative refe
...