OK... Now that Earth Control has re-established my orbit...
Yes, a PRV controls incoming water pressure from the municipal system. Depending on the PRV model/style, it may or may not allow excess house pressure to bypass it and return to the municipal system.
The OP stated that he has a PRV installed and adjusted to 45PSI max. but has tested water pressure to 90PSI at times with a test gauge. He did not say what the pressure was when the gauge was installed but over a time period just the max pressure @ 90PSI
he did say what the pressure was gauge was installed, it was 45 psi,
then, he noticed pressure creep to 90 psi,,,intermitenly
(actual supply pressure is not known).
According to the city, water pressure is 90 psi
with a need for expansion tank, the pressure would not stop at 90
it would rise
T&P valves are 150 psi not 125
So that would indicate to me...
... that a thermal expansion event is happening. The TPRV is calibrated (if functioning properly) to release pressure @ 125PSI. A TET is needed so as to absorb the excess pressure, not wait until the TPRV fully opens (not dribble) and release the excess pressure (at it's high setting damage in the system may all ready have occurred)
The TPRV is for emergency protection only, not to be allowed to dribble to hopefully control high pressure(s) in the system. It may lead to early valve failure.
incorrect, they do dribble, that is the first indication you have a problem
Before replacing anything, the OP has to diagnose the problem from square one. Regardless, code now calls for a TET install when a non-back flow PRV is installed.
I'm trying to figure out what is causing spikes in my water pressure in my home. i have my PRV set to 45 psi, no expansion tank, no back flow preventer or check valve.
Street pressure according to water company is around 90 psi.
I've installed a pressure gauge with the red pointer on an outside faucet that shows pressure max and have seen it as high as 90 psi. Just cracking a faucet sends it back to 45 psi. Could my water heater still be the problem? Could my three year old PRV intermittently be leaking by? Should I even worry about this?
Thanks, Curtis
Temperature and Pressure (T&P) relief valves
Temperature and pressure (T&P) relief valves used on residential water heaters are typically designed and manufactured to relieve on pressure at 150 psig and on temperature at 210 degrees F. These ASME, ANSI and CSA (AGA) approved relief valves protect the water heater from excess pressures and temperatures by discharging water.
In normal operation of the water heater and T&P valve, no water should be discharged from the valve. A T&P valve that discharges is an indication of an abnormal condition in the system and by discharging, the T&P valve is meeting its designed safety purpose. The causes of discharge can be thermal expansion, excess system pressure, low temperature relief, too high a setting on the water heater, or something in the water heater causing excess temperatures in the heater.
Thermal Expansion: When water is heated it expands. In a 40 gallon water heater, water being heated to its thermostat setting will end up expanding by approximately 1/2 gallon. The extra volume created by this expansion has to go somewhere or pressure will dramatically increase, such as when water is heated in a closed system.
A good indication of thermal expansion is when the T&P valve releases about one cup of water for each 10 gallons of heater capacity with each heating cycle. The T&P valve is functioning properly when it relieves pressure caused by thermal expansion, but frequent relief can build up natural mineral deposits on the valve seat, rendering the valve inoperative. This condition can be addressed by the installation of a Watts thermal expansion tank or other Watts thermal expansion device to protect your system from overpressure caused by thermal expansion. If there is no discharge from the valve, there is no need to replace the valve.
System Pressure: If installation of a thermal expansion device does not relieve
occasional dripping from the T&P valve, then the system pressure should be checked. If system pressure is excessive (typically more than 75 PSI), a Watts pressure regulator should be installed on the incoming water line.
Warning: The discharge from a T&P valve can be very hot. It is very important that all T&P valves be installed properly with a discharge line piped downward to an adequate drain to avoid property damage and to minimize possible human contact. Please read and follow the instructions on the warning tag attached to your T&P valve.
question, why, in your opinion, would a system that has been working
with out any problems, all of a sudden require a expansion tank ?
would it not be a logical conclusion, that a part of the system has failed ?
would it not be in the best interest of the client to find the part that has failed.?
I agree, the op needs to inspect the system to find the CAUSE
not mask the symptom by installing an expansion, and calling everything good. the original problem still exists,
time for school.
how would he diagnoses that it is the prv causing creep and not expansion ?
