T&P valve replaced - Not Helping

Problem started yesterday. Hot water was running from pipe coming off the T&P value. Replaced value but it did not help. The water was still running from the pipe at approx. 4 gallons in 30 - 45 minutes. The water heater is off and both of the water heater incoming lines are off. Water starts running out as soon as the cold line is turned on. I believe we have a PRV located before the main shutoff. We bought the house 1 year ago and have had no problems until now. Any help would be appreciated.

check your water pressure

buy a pressure guage [there cheap,home or lowes ,or hardware store]

they screw on to outside hose bib. make sure it's one after pressure reg.

my guess if you replaced the w.h. blow off valve. with a new one you have a press. reg. problem. you may also need a air /bladder tank on cold line
can't recall proper name - grtting OLD HA HA

Based on what you have told us, your PRV has failed, and is allowing your house to creep up to street pressure. A TP valve will usually start dripping at pressue of 120, and flow will increase until at 150 PSI is will be wide open.


High pressure cause damage in the house. Washin machine hoses are particularly prone to bursting. Fix this problem right away.

Just a thought

When you get one of those pressure gages, that screw on to your hose bib, you can get one that has a needle that will tell you the highest pressure ever hit in any given time. In other words you can leave this gage on for 24 hours, because some times the pressure will get higher, at night, when the demand is low. My personal opinion is that anything over 70 psi, is too high.
If you are good a soldering, you can pick up a “whole house†pressure reducer†at Home Depot. They do have different styles, and sizes so you may want to get some advice at the store from one of the associates.
Make sure before you go to the store, of your incoming water line pipe size, and type, (copper or galvanized etc). Also make sure there is enough room to install it, (usually in the front of your house, where the main enters the house).

I does sound like the PRV has failed and that the TPV is working properly. Interesting enough, with a PRV operating properly, you will have a closed system and this will cause the TPV to open also. Briefly, when water heats in the tank, it expands and must have somewhere to go. The PRV prevents the pressure from going back into the water main, so the TP opens to relieve the excess pressure. This is remedied with an expansion tank installed in the cold water intake between the PRV and the water heater. While you are at all of this, why not install a pressure gauge between the expansion tank and the PRV so you can check the pressure occasionally. This topic was extensively discussed not long ago, you can go back and read those comments.

Pressure in excess of the T&P valve setting (usually 150#) will cause weeping up to a slight stream.

Temperature in excess of 210° will always cause the valve to open fully, in an effort to cool the tank.

There is ALWAYS a reason behind a leaking T&P valve, the leaking is an indicator of a problem. The only time I've seen the T&P to be the only problem is if it's been operated by someone and has become fouled with debris.