Thread: Pex pressure test

'Converstion with a plumber yesterday - he mentioned that he tests pex with 120 psi. Sounded high to me, but, I don't know. Anyone??

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I dont see a problem with that..A few specs below.


PEX tubing can be used up to 200° Fahrenheit for heating applications. For plumbing, PEX is limited to 180° F. Temperature limitations are always noted on the print line of the PEX tubing.. PEX systems are tested to and can be used with standard T and P relief valves that operate at 210” F and 150 psi.

Higher than he needed to, but that's a good thing. Sounds like a good plumber who wants any failures to happen when he is still there, so he tests if higher than required.

From the 2006 IRC. (underlining and bold are mine)
- P2503.6 Water-supply system testing. Upon completion of the water-supply system or a section of it, the system or portion completed shall be tested and proved tight under a water pressure of not less than the working pressure of the system or, for piping systems other than plastic, by an air test of not less than 50 psi (345 kPa). This pressure shall be held for not less than 15 minutes. The water used for tests shall be obtained from a potable water source.

All plastic supply piping systems are to be tested to the working pressure of the system by a hydrostatic test, not an air pressure test.

- P2903.3 Minimum pressure. Minimum static pressure (as determined by the local water authority) at the building entrance for either public or private water service shall be 40 psi (276 kPa).
- - P2903.3.1 Maximum pressure. Maximum static pressure shall be 80 psi (551 kPa). When main pressure exceeds 80 psi (551 kPa), an approved pressure-reducing valve conforming to ASSE 1003 shall be installed on the domestic water branch main or riser at the connection to the water-service pipe.

Thus, the "working pressure of the system" can reasonably be taken to mean "80 psi".

When I was inspecting two 26 story high-rise buildings plumbed with copper, the plumber would test to anywhere between 150 psi (minimum) to 200 psi. If there was going to be a failure or a leak, he wanted to know while everything was open and accessible. More than once, the plumber's men 'forgot to solder' one or more fittings, and when the system was pumped up, it would blow apart at those fittings - what a mess it made.

Instead of leaving the pressure on for 15 minutes, he would leave it on overnight, are even over several days.

Thanks, Jerry, Ted.

Originally Posted by Fritz Kelly

I don't see that as excessive, it should be able to withstand that. HOWEVER, alot of the pex I see has 100 PSI stamped on it.

No it doesn't. Show me a photo.

Well, no, I take that back. It DOES have 100psi stamped on it, but that's a somewhat incomplete quote. It'll say something like 180psi at 70*F, 150psi at 100*f, ... 100psi at 200*F, meaning that as the temperature goes up, the pressure rating goes down. But that's not the same as saying pex can't handle over 100psi.