Faucet surges and leaking T&P valve

[maitiu]

I'll try to keep this as short as possible while giving all relevant info.

About a month ago we started getting random high pressure surges in our water faucets, and at the same time our 20 year old water heater started leaking from the T&P valve. We decided to replace the water heater since it was so old anyways. Upon getting the new Rheem tank installed, same size as the previous, it immediately started leaking from the TP valve as well.

Rheem sent a new TP valve but advised that it probably wouldn't matter, they think it's doing what it is supposed to. I have not installed the new valve yet because I tend to agree that the problem is somewhere else. We still have random surges in our faucets, and the TP valve leaks if the temp gets turned up to anything past the lowest setting.

Rheem suggested installing an expansion tank, but we haven't had one for the six years we have been in the house and have never had a problem until now. We do have a pressure reducing valve on our incoming water line. My only other thought is, could that be going bad?
Our faucets might surge for 1 or 2 seconds when you first turn them on but are fine after that.

Any other thoughts or suggestions would be greatly appreciated.

Thanks!

 

[gr8rcfan]

I am also looking for a similar answer. My home is 20 yrs old. I have a 2.5 gal mini tank that is 6 yrs old under the kitchen sink because the kitchen is so far away from the main water heater. A couple of weeks ago, we started getting water in the cabinet from the T&P valve. (it does not exit to a drain). We replaced the valve - no help. There's no constant leak, but it would seem it expels about a pint of water, sometime during each 24hr period. Is this due to a surge? Our main water heater seems OK. No leaks from it's T&P valve. Why has everything been fine for 20 yrs, then just start happening on it's own? Just like Maitiu, any thoughts or suggestions would be greatly appreciated.

Thanks!

 

[KULTULZ]

I have a 2.5 gal mini tank that is 6 yrs old under the kitchen sink because the kitchen is so far away from the main water heater. A couple of weeks ago, we started getting water in the cabinet from the T&P valve. (it does not exit to a drain). We replaced the valve - no help. There's no constant leak, but it would seem it expels about a pint of water, sometime during each 24hr period. Is this due to a surge?

Our main water heater seems OK. No leaks from it's T&P valve. Why has everything been fine for 20 yrs, then just start happening on it's own? Just like Maitiu, any thoughts or suggestions would be greatly appreciated.

Thanks!

By any chance, did the manufacturer of the tank heater recommend a TET (Thermal Expansion Tank) on the circuit?

Also, the TPR valve needs to be plumbed to drain safely.

Shown is a BOSCH install-

 

[KULTULZ]

The pressure surge(s) can only come from two sources, municipal water with no PRV or bad/misadjusted PRV, or thermal expansion from a tank water heater.

The water pressure has to be gauged to find either (or both).

 

[KULTULZ]

thermal expansion-

one of the more common question regarding t&p relief valves is why they drip. In most cases, dripping is caused by thermal expansion. When water is heated in a closed plumbing system, it expands,causing an increase in pressure. This increase in system pressure over that regulated by the pressure reducing valve is called thermal expansion pressure. The t&p valve (tprv) is a safety device and is not intended for continuous operation to relieve thermal expansion.

continuous dripping can cause the build up of mineral deposits on the valve and may render it useless. A simple way to detect whether or not
thermal expansion is the cause of a dripping relief valve is to open a fixture during the expansion period. Opening a fixture opens the system, and immediately the pressure will drop back to normal. A second method that is used to determine the maximum pressure of the system is to install a pressure test gauge with a telltale on a hose bibb connection. As the pressure increases, the gauge moves the telltale.

By leaving the gauge on the system for 24 hours, the telltale will remain at the
highest pressure registered on the system.

- watts tech info -

 

[maitiu]

I did put one of those gauges outisde on the hose connection and checked it every couple of hours. Every time I looked at it, it had peaked at around 130 psi. Without any water running it was sitting at around 40 psi though. Is this more indicative of needing an expansion tank instead of having a bad pressure reducing valve? If so, what would be the cause of needing an expansion tank all of the sudden when I haven't had one before?

 

[frodo]

A PRV, If installed correctly, and in working order will not allow pressure surges with a full swing that you are describing

IF, you have a prv, the first thing you do, is check the PSI on BOTH sides of the prv.

This will tell you if the PRV is working

example. 120 psi on both sides. not working
120 on street side, set at 60 psi, but 80 on house side, prv not working

after, you have determined the prv is good, THEN move to an expansion tank.

but to be honest, if you are experiencing 130 psi peaks, prv is bad or you need one