I have a 3 year old gas water heater with an expansion tank. The water temp is set to 120 degrees. For the last couple weeks, the discharge line has been leaking water out of the overflow pipe. I've been told that simply replacing my T&P valve will not solve this problem. I had my water heater inspected and the person said the water pressure regulator (Pressure Reducing Valve on main line) is not controlling the flow into the system when static. With no water flowing the pressure tested at the tank valve (Water Heater drain faucet) was 140 PSI. When you start a faucet running in the house the pressure dropped to 60 PSI. Then, with the water turned off, it very slowly started creeping back up and after 10 minutes and was at 75 PSI and rising. So, I would appreciate anyone's feedback as I'm finding it hard to believe that I have to pay to have my PRV replaced on a 3 year old house. Also, the Expansion Tank was tested as is working correctly. Thanks

Your PRV is doing what it is supposed to do, blows off when the P of a PRV is too high. They blow at 150 psi or around 200 degrees. You need to have a pressure reducer installed for the whole house supply. You must be living directly under the city water tower. What does your city water departmnent have to say about this issue, you can't be the only person with the problem.

Ballengerb1 - Thanks for the response, but I already have a Pressure Reducing Valve to lower the flow coming into the house. That's the item I'm concerned is not working, because when water isn't flowing the pressure reads 140, but when it is flowing it goes down to 60 and then goes back up. Let me know what you think.

I think I would replace the pressure reducing valve and wait on the P&T. Replacing the P&T is not a particuraly difficult task. You close the cold water input valve, open a hot water faucet to relieve the preasure. You then cut the pipe, unscrew the pipe stub from the P&T, unscrew the P&T from the heater and screw in the new one. Screw the pipe stub into the new P&T and reconnect the rest of the pipe with a coupling.

I agree with hk.

Thanks for the replies. Sounds like replacing the PRV is the best option.

Thanks for the replies. Sounds like replacing the PRV is the best option.
In my book replacing the PRV valve is the only option. What's all that extra pressure doing to the rest of the system? Over pressuring your water system puts a strain on everything. Your pipes, your faucet cartridges, Toilet ballcocks if the pressure's strong enough to push past the seat and it will also open the T & P valve on your water heater. Call your water company and ask them what the pressure is in the main feeding your house. 45PSI is the normal house pressure. Up to 55 acceptable but if you have any more then that I replace the PRV valve at once. Good luck, Tom

Speedball1, Thanks for the response. What's strange is that ever since the Water Heater inspector checked the pressure on the drain of the water heater, the water has stopped flowing out the discharge pipe. But, it's only been two days. Kind of odd how it would just stop like that after leaking for two weeks. However, I'm concerned about the leak coming back if I don't get the PRV replaced/repaired.

And what was the pressure when the inspector checked it? Tom

He put the gauge on the faucet coming out of the bottom of the water heater and it read 140. Then he had me turn on a hot water faucet and let it run for a few minutes. The pressure went down to 60. He left the gauge on and you could see it move up, but very slowly. I'd say we talked for about 10 minutes before it went above 70 PSI and then he removed it.

I think several of us would still recommend a new pressure reducing valve. Just because your leak stopped it doesn't mean every fixture in the house isn't stressed. Try to get down to 40-50 psi.