New PEX passed an air test, then dozens of crimps wept: why street pressure over 80 psi matters
A new-home owner on Reddit's r/Plumbing says the house's PEX held a 70 psi air test, yet dozens of crimp joints wept once the water came on at more than 80 psi. A pressure-reducing valve set to 55 psi stopped the leaks. The International Residential Code caps static pressure in a house at 80 psi.
The owner described small weeps at many crimp rings soon after the system was filled, and a street pressure reading above 80 psi. Once a pressure-reducing valve set to 55 psi went in, the weeping stopped, according to the post.
The pressure limit is in IRC Section P2903.3.1: static water pressure in the house may not exceed 80 psi, and where the main runs higher, an approved pressure-reducing valve meeting ASSE 1003 or CSA B356 goes on the line at the water service connection. The IRC also calls for a device to control thermal expansion when a check valve or similar device traps pressure from a storage water heater.
Testing is the second issue. IRC Section P2503.7 requires a new water system to be proved tight with water at no less than the system's working pressure, held for at least 15 minutes. Air or other gas may be used on PEX only where the pipe and fitting makers' instructions specifically allow it. In this house the air test ran at 70 psi, below the street pressure the joints had to hold once water was on.
The crimps themselves are the third check. Makers of ASTM F1807 crimp tools, such as IWISS, say every ring should be checked with a go/no-go gauge, which confirms both the crimp and the tool's calibration. Before closing walls, ask the plumber for the static pressure reading at a hose bib, the test method and pressure used, and whether every ring was gauged.
Why it matters: Put a gauge on a hose bib before rough-in and again at final. If static pressure tops 80 psi, the IRC requires a pressure-reducing valve; then check whether the water heater now needs expansion control. On crimp jobs, gauge every ring and test with water at working pressure unless the maker allows air.
Sources
- P2503.7 Water-supply system testingInternational Code Council, Oct 29
- P2903.3.1 Maximum pressureInternational Code Council, Oct 29
- CL 1" ASTM F1807 PEX Pipe Crimping Tool, for 1-inch Copper Pex Crimps Rings, with Go/No-Go Gauge, Angled HeadIWISS Tools, Oct 29
- Can high water pressure cause small weeping leaks in Pex??Reddit r/Plumbing, Oct 29