Posting this to help others and hopefully prevent major disaster/flooding.

In my 10 year old house, noticed very high water pressure.

Symptoms:
1. large gush of water when turning on faucets
2. toilet valves were not shutting off completely. I initially thought that the original American Standard valves(ball/float) were to blame, so I replaced them with Fluidmaster 400a. This symptom stopped, but the underlying high-pressure problem was not fixed.
3. sudden dripping of water from shower head, even though fixture had not been used in a few hours. This is a major red flag that the system is under very high pressure and the weakest point in the system is now leaking.

Measured water pressure at exterior hose bib using gauge from Home Depot. Found pressure over 210 psi. It was likely quite a bit higher at peak.

3 problems were found:
1. WATTS expansion tank had no air charge. 0 psi. Cause: air slowly leaks out.
2. WATTS PRV was not holding pressure due to debris(tiny rocks) in stuck in rubber valve seat. Cause: debris coming from city water main.
3. T&P valve failed to open at 150psi setting. Cause: T&P valve will stick/corrode shut due to hard water deposits, if valve is not cycled/tested often(ie: once per year).

These problems, combined with water expansion after using lots of hot water(ie: filling bathtub) caused a very high pressure situation.

Resolved by replacing: PRV, expansion tank, T&P valve.

Future plan:
1. Water pressure is tested monthly to ensure PRV is not starting to fail.
2. Expansion tank pressure is tested every 6 months to detect air pressure loss. Refill as needed.
3. Test T&P valve annually by lifting the lever.

Check your water pressure. I now believe that many random plumbing problems may have high water pressure as a root cause.

Note: the above problems are directly related to a "closed system" where high water pressure can not be forced back into the city water main due to a check valve.

Note: city water pressure at street is 75 psi

Let me know your thoughts on this. Have I covered all the bases? Would you have done anything differently?



Edited 2 times.

Why have a PRV, if street pressure is 75psi. Most(all?) codes allow 80psi before PRV is required. No PRV = no need for expansion tank or pressure checks.

Steve agrees with Steve. The high pressure readings were probably from hot water expansion. You could remove the PRV and any check valves and replace with permanently installed pressure gauge. And don't forget to replace the relief valve on the water heater.

[www.waterheaterblast.com]

the 'closed system' may be caused by a check in the meter itself (ain't the new stuff fun?)

however, if city main is 75 a PRV is NOT needed

TPRV at heater is ALWAYS required - will relieve at 150 psi OR 210 degrees

Expansion tank is required due to closed system

optional: Watts RV set for (imo) 100 psi (see: [www.watts.com] )

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Since this is fairly new construction (10 years old) by a large tract builder, I doubt the PRV would have been originally installed(at additional cost) unless required by the plumbing inspector. Also, the street pressure is at 75 today, but may increase during the night, or it may have been higher 10 years ago before a bunch of new houses were added to the development.

I am keeping the PRV for now. Also, I have it set to 50 psi which is sufficient for our needs. The PRV is really not a factor in any of this, but I am just mentioning for completeness. My Watts PRV does have a thermal bypass.

About the check valve, it is at the water meter and can't be removed.

The intention of my post is to raise awareness about what can happen if the T&P valve fails closed, and/or the expansion tank loses all air pressure and becomes ineffective. I'd like to see everyone start checking the health of things on a regular basis.