Information on the most widely used ASTM standards within the materials testing industry
ISO 13255 Thermoplastics piping systems for soil and waste discharge inside buildings – Test method for airtightness of joints.
ISO 13255 specifies a standardized approach to evaluate the airtightness of joints in thermoplastics piping systems used for indoor soil and waste discharge, ensuring reliability in building drainage applications.
Test Principle
The core principle is to subject a joint assembly to a defined internal air pressure for a set duration while monitoring for leaks. The test validates whether the joint can maintain airtightness under static pressure and, optionally, angular deflection (simulating real-world stress). Leaktightness is confirmed by the absence of bubbles (from a soap solution), water escape, or component damage. The standard assumes reference standards will specify critical parameters (e.g., sampling rules, number of test pieces).
A test assembly of pipes and/or fittings is subjected to a given internal air pressure (0.1 ± 0.01 bar) for a specified time period (5 minutes) while the leaktightness of the joint is verified by inspection with soapy water solution. If applicable, the joint is also manually deflected to maximum angular deflection (as per manufacturer specifications) in four directions (0°, 90°, 180°, 270°), maintaining each position for 1 minute. The principle assumes that test parameters like sampling procedure and number of test pieces are set by the referring standard.
Test Methods of ISO 13255
ISO 13255 describes a pressure decay test method with angular deflection specifically designed for joints in thermoplastics soil and waste discharge piping systems. The method involves subjecting the joint assembly to internal air pressure while simultaneously checking for leaks using a soapy water solution, and applying angular deflection to simulate real-world installation conditions.
Test Equipment requirement of ISO 13255
Same like ISO 13259, ISO 13254, recommend UnitedTest Piping System Joints Leak Tightness Tester , Include:
End-sealing devices: Sized and sealed to match the joint type. They are restrained to avoid longitudinal forces on the assembly, prevent separation under pressure, and not influence angular deflection. Their mass must not alter the joint’s alignment.
Air pressure source: Connected via a shut-off valve to an end-sealing device, capable of maintaining the required pressure within ±10%.
Pressure-measuring device: Verifies compliance with the target test pressure.
Water supply/outlet devices: Each connected via a shut-off valve to an end-sealing device, used to fill the test piece to half the pipe’s internal bore.

Auxiliary parts include fixed points, sealing plugs (with water outlets/inlets and end restraints), loose bushes (for universal pipe sizing), and fixed components.
Test Specimen
One end of the assembly uses a pipe/fitting with a spigot mounted in two clamped blocks. The joint is assembled with a fixed component’s open end, then sealed with plugs—one of which has a central water outlet and shut-off valve. Assembly follows manufacturer instructions, using the smallest available spigot end and largest available socket/groove diameter.
Test Application (Industry Field)
ISO 13255 is specifically designed for thermoplastics piping systems used for soil and waste discharge inside buildings. This includes:
Residential buildings
Commercial buildings
Industrial facilities with internal soil and waste drainage systems
HVAC drainage systems
Applications where airtightness of joints is critical to prevent:
Odor leakage into occupied spaces
Contamination of building interiors
Reduced system performance due to air ingress/egress.
Step by Step Test Procedure of ISO 13255 Plastic pipe and joints airtightness test
| Mounting | Install the test piece horizontally in the apparatus. |
| Leak Monitoring | Record leaks (soap bubbles, water escape) throughout testing. Apply soapy water (or equivalent) to the spigot-socket annular space; wipe excess. |
| Valve Setup | Open the water outlet valve; close the air inlet valve. |
| Water Filling | Open the water inlet valve. When half-full (indicated by outlet flow), close the inlet valve first, then the outlet valve. |
| Pressurization | Open the air inlet valve; increase pressure to (0.1±0.01) bar (using air at 5.1 temperature; 1 bar = 0.1 MPa = 10⁵ Pa). |
| Pressure Hold & Deflection | Maintain pressure for 5 minutes. Then manually deflect the fitting/joint on the spigot end to the manufacturer-specified maximum angular deflection, applying this at 0°, 90°, 180°, and 270° for 1 minute each. |
| Post-Test Inspection | Depressurize, drain, and dismantle the test piece. Inspect and record any changes in component appearance. |
Related products and device
Related Standard
ISO 13259 Leak tightness test Thermoplastics piping for underground non-pressure stipulated determining method of the leak tightness of elastomeric sealing ring type joints buried thermoplastics piping. This standard specifies three basic test pressures for determining the leaktightness of elastomeric sealing ring type joints for buried thermoplastics non-pressure piping systems.
ISO 13259 Leakage tightness test machine.
Unless otherwise specified in the referring standard, the methods pressures used are the following:
- p1: internal negative air pressure (partial vacuum);
- p2: a low internal hydrostatic pressure;
- p3: a higher internal hydrostatic pressure.
ISO 13844 specifies a method for testing the leak tightness under negative pressure, angular deflection, and deformation of assembled joints between elastomeric-sealing-ring-type sockets made of plastic or metal and plastic pressure pipes.
ISO 13254 specifies a hydrostatic pressure test method for evaluating the watertightness of two categories of non-pressure thermoplastics components: (1) multi-piece fabricated products (e.g., custom-molded fittings) and (2) joints in thermoplastics piping systems.The test validates sealing performance under simulated service conditions for drainage, sewerage, and stormwater systems.
The standard aims to ensure consistent assessment of leak resistance, critical for applications like drainage, irrigation, and underground conduits where fluid ingress could compromise system integrity.
EN 1277 specifies test methods for assessing the leaktightness of elastomeric sealing ring type joints used in buried, non‑pressure thermoplastics piping systems, such as those for drainage and sewerage. The standard defines three test pressures (partial vacuum, low hydrostatic pressure, and higher hydrostatic pressure) and four test conditions (with or without diametric and/or angular deflection).
FAQs about ISO 13255 (Airtightness Test for Soil & Waste Pipe Joints)
Q1: What is ISO 13255 mainly about?
A: ISO 13255 specifies an airtightness test method for joints in thermoplastic piping systems used for soil and waste discharge inside buildings. It checks if joints prevent air/gas leakage under pressure and angular deflection.
Q2: Why is this test so important?
A:Stops foul air, odors, and harmful gases (H₂S, methane) from entering rooms.
Ensures drainage system pressure balance and proper function.
Meets building code and health/safety requirements.
Verifies joint quality under real installation misalignment (angular deflection).
Q3: What test pressure and duration are used?
A:Test pressure: 0.1 ± 0.01 bar
Holding time: 5 minutes
Each angular deflection position: held 1 minute
Q4: What equipment is mandatory?
A: Sealing plugs, air compressor, pressure gauge, deflection fixture, soapy water leak detector, clamping device.
Q5: How is leakage judged?
A: Continuous bubbles from the joint (soapy water) or water escape = FAIL. No bubbles = PASS.
Q6: Common reasons for test failure?
A: Improper assembly, damaged gaskets, out‑of‑tolerance pipe/fitting dimensions, insufficient insertion depth, weak joint design, excessive deflection.
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