Short answer
Screw a pressure gauge onto an outdoor hose bib with everything inside off. Readings over 80 psi are too high, and many plumbers aim for 50 to 70. High pressure usually means the pressure reducing valve (PRV) on your main line has failed, and replacing it protects every fixture in the house.
Signs of high pressure
- Banging pipes when valves close
- Toilets that run or refill on their own
- A dripping water heater relief valve
- Burst washer hoses or failed supply lines
How to test
Buy a hose-bib pressure gauge at a hardware store. Attach it to the hose bib closest to the main line, open the bib fully with everything inside off, and read it. For a fuller picture, use a gauge with a max-reading needle and leave it overnight, since pressure often rises at night when demand drops.
What a failing PRV looks like
PRVs wear out, commonly in 10 to 15 years in the Valley. A failed PRV may let full street pressure through or creep up over time. Adjusting a worn valve rarely holds, so replacement is the usual fix.
When to call a plumber
- Your reading is over 80 psi.
- The pressure creeps up overnight.
- The relief valve on the water heater is dripping.
What the plumber does: see pressure regulator (prv) replacement.
Common questions
Does high pressure cause slab leaks?
It adds stress to every pipe and joint. It isn't the only cause, but it can speed up failures in aging pipe.
Editorial note: this guide is general information for Phoenix-area homeowners, not a diagnosis. Conditions vary by home, so a licensed plumber should confirm the cause before any repair.