Problem started with water coming out of the water heater discharge tube. Water heater (GE) is 5 years old. The plumber replaced the PRV. Water still discharges from tube. Discovered that the water pressure was up to over 100psi at times. It was assumed the town water pressure coming into the house was too high, so installed pressure reducer in system. Pressure still over 100 at times with pressure reducer. Then the hot water tank was isolated from the plumbing system with shut-off valves for purposes of testing water pressure of system without hot water tank - the water pressure measured 50 psi without HW tank connected. So problem must be with water heater, right? When the breaker to the HW heater is off, pressure of system is 50 psi. When the tank is on, it fluctuates between 50 and 120psi. What is the problem with the tank? can it be repaired? Any help would be greatly appreciated. Thanks.

The "problem" is that he installed a presssure regulating valve, WITHOUT also installing a hot water expansion tank. The PRV created a "closed system" so when the water is heated it expands. Because water is basically "non compressible" ANY expansion will create an increase in pressure> The amount of increase will depend on how much it has to be heated, and how many gallons of water is heated. Install an expansion tank and it will minimize, but NEVER stop, the pressure increase when the water is heated.

Thanks for responding. Water released from the discharge tube and the water pressure measured very high before the reducer was installed. The first 3 years after the tank was installed there was never a problem with water coming out of the discharge tube. Was it a "closed system" before the reducer was installed?

Hj, ( not to hijack the post ) I have an 80 gallon electric wh and I dont have an expansion tank and never had an issue...are you saying ALL electric wh's SHOULD have an expansion tank ?

no, all houses with a pressure reducing valve should have an expansion tank.
why the sudden increase in pressure, ??????

To the OP....hj's answer was based on your own testing (current). When the water is not heated, your pressure is normal. What "was" is no longer relevant. If there is a potable water expansion tank, already, it has failed. If there isn't one, you need one.

Paul48, Thanks for responding. HJ said the problem is a result of the pressure reducer being installed without an expansion tank. But the high pressure and water being released from the discharge tube were there before the pressure reducer was installed. Additionally the HW tank never released water through the discharge tube during its first few years..... so it seems like something must have changed with the HW tank after the first few years and we may be masking the problem with the installation of the expansion tank. No? (system has never has an expansion tank).

If could be if there was a check valve somewhere, such as in the meter. But, by definition, the pressure could NOT increase in an "open system" unless the city pressure also went up.

ANY TIME water is heated, it expands. If there is no where for it to expand into, such as an open system or an "expansion tank", the pressure HAS to increase. ONe of the laws of physics, which is the basis for hydraulics, is that a liquid, such as water, is not compressible. But, we do NOT know if you have a closed system or not.



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The ONLY way pressure can increase is if "something" increases it. And, that "something" requires additional energy, such as a pump, it does NOT 'Just happen'.

HJ, Since the pressure did increase when tested (over 100 psi) before the reducer was installed are you saying it MUST be a closed system? There is a water meter in the basement - do they typically prevent water flow from flowing backwards? The water meters were added by the town about 6 years ago and they did have problems with a few - but mine was checked at the time and given the OK.

Is there any new housing developments in your neighborhood ? Some towns have been known to increase the pressure when new developments are built instead of have to replace and increase the size of the water mains in the street.

Either the city pressure increased or you had a closed system. There are no other possibilities.

Does a water meter create a closed system ?

some water meters have built in check valves and some don't.
call your local DPW and ask. they will know.

They CAN. It depends on the water meter model.



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I will have the expansion tank installed. I understand there will be a rise in pressure when the HW tank is heating, but is it in the "normal" range for pressure to go from 50psi to over 120psi in less than 1/2 hour? The pressure eventually gets to over 150psi because that is the relief point of T&P valve and water does come out of the discharge tube. My plumber believes the expansion tank will not get the pressure down below 80psi which is the recommended max pressure for the plumbing system. Thanks for all the help.

The expansion tank will modulate the pressure rise, regardless of what that is even if it is over 80 psi, which is unlikely. IMMEDIATELY, after you open a faucet the pressure will drop to the setting of the PRV.

Charge the expansion tank air at whatever pressure you set the PRV to.