Pressure testing PEX and PE-RT tubing systems with compressed air or inert gas
Follow the manufacturer’s instructions and ensure all testing is performed in accordance with local codes and regulations.
By Lance MacNevin
PE-RT tubing installed for a radiant heating system. Image courtesy of CB Supplies.
Pressure testing of a completed piping system is typically required by both local codes and pipe manufacturers to ensure pressure tightness. In the construction of piping systems such as hot- and cold-water plumbing distribution, fire protection, water service, hydronic heating and cooling and snow- and ice-melting systems, it is sometimes difficult to test systems using pressurized water because of freezing conditions, insufficient water supply or insufficient water pressure. In certain cases, pressure testing using compressed air or an inert gas such as helium or nitrogen may be a preferred solution.
However, some types of plastic pipe and fitting materials are not suitable and not permitted to be tested with compressed air or gas, due to the possibility of breakage with shards being discharged, potentially harming people or property.
Fortunately, crosslinked polyethylene (PEX) and polyethylene of raised temperature (PE-RT) are flexible tubing materials that are not subject to brittle failure and are typically safe for testing with compressed air or inert gas. These tubing materials are stronger than most would imagine, with a minimum short-term burst strength of 475 psi at 73° F, according to industry standards, yet remain flexible even at temperatures well below freezing.
Therefore, it is the recommendation of the Plastics Pipe Institute, Inc. (PPI) that PEX tubing systems produced in accordance with ASTM F876, ASTM F3253, AWWA C904 or CSA B137.5 be permitted to be tested with compressed air or inert gas, provided that the manufacturer’s instructions are followed and that all testing is performed in accordance with local codes and regulations. This recommendation also applies to PE-RT tubing systems produced in accordance with ASTM F2623, ASTM F2769, or CSA B137.18.
The Plastics Pipe Institute, Inc. (PPI) recommends that PEX tubing systems produced in accordance with ASTM F876, ASTM F3253, AWWA C904 or CSA B137.5 be permitted to be tested with compressed air or inert gas, provided that the manufacturer’s instructions are followed and that all testing is performed in accordance with local codes and regulations. Image courtesy of PPI.
From a review of the latest model codes, IAPMO’s UPC, UMC, and USHGC each permit PEX and PE-RT tubing to be pressure tested using air. Also, ICC’s IPC, IMC, and IRC permit PEX tubing to be pressure tested using air. The National Plumbing Code of Canada permits the use of air pressure tests unless “…a manufacturer states that an air pressure test is not recommended…”
Test pressures
PPI’s generic recommendation for plumbing and mechanical piping systems is for the test pressure to be at least equal to the expected working pressure of the system, not less than 50 psi (345 kPa), and not greater than 160 psi at 73° F (1,100 kPa at 23° C), or as recommended by the tubing manufacturer.
However, keep in mind that certain codes require different minimum pressures, and some codes require that piping is tested to withstand 1.5 times the system operating pressure. Be sure to follow local requirements.
Also, it is very important to not exceed the pressure rating of any tested component. For systems that incorporate plastic fittings, valves, or manifolds, air testing shall be in accordance with each component manufacturer’s instructions. If the manufacturer of any pressurized component does not recommend air pressure testing at the required pressure, then that component must be isolated or removed from the system prior to an air pressure test.
PEX tubing installed in a plumbing system. Image courtesy of Uponor.
Safety concerns
Compressed air or inert gas used for pressure testing has high potential (stored) energy. Any uncontrolled release of that energy can present serious safety hazards, such as an unsecured fitting being shot across a room at high speed like a projectile.
Therefore, here are several recommendations to ensure safety when testing PEX and PE-RT tubing systems with compressed air or gas:
- Only authorized people should be in the proximity of the tubing systems during the testing procedure and must be wearing the appropriate personal protective equipment;
- Any incomplete or unrestrained fitting could become a projectile during pressure testing. Therefore, all fittings and valves must be installed correctly and inspected before testing;
- Because of the flexible nature of PEX and PE-RT tubing, failure or separation of the tubing from a fitting or restraint may cause unrestrained tubing to whip or lash about as the energy of the suddenly decompressing air or gas escapes. Tubing must be properly restrained to prevent or limit whipping in these cases. All fastening and securing requirements of the PEX or PE-RT tubing manufacturer and local codes must be followed;
- Tubing systems which are being tested with air or gas should be labeled as being under pressure to indicate that air pressure testing is underway; and
- PEX and PE-RT tubing systems must be depressurized before any work is performed on any portion of the system, such as adjusting or inspecting a fitting or adding additional restraints to the tubing.