My pressure relief valve on the hot water heater is releasing every couple of days. My tank is in an overflow pan. I get about an inch of water in the pan each time. We've replaced the hot water heater. Before that, we replaced the pressure relief valve (twice) on the old water heater. Problem seems to be getting worse since it's gotten colder. Plumbers have been scratching their heads on this one. We have 61 psi coming in from the street. I have an expansion pressure tank and it is installed on the outlet/system pipe approx. 3 feet from the tank. It's a gas heater, 8 months old. The expansion tank might be 8 to 10 years old. I purchased the home a year ago. My plumber thinks we need to start with a pressure regulator valve in the service line. Looking for suggestions?? Thanks.

I think expansion tanks normally go on the inlet, but see no reason why one on the outlet shouldn't work. That is unless it is waterlogged. If it has an air valve on it, push in the stem and see if water comes out. If so, it is bad. If no air valve, start at the bottom hitting it with a screw driver handle. If half way up it changes from clunk to clang, it is OK. If it is clunk all the way to the top, it may be bad.

I will also add:

If you are on city water and have no pressure regulator, I would strongly suggest getting one, I am on city water, and I noticed that my water pressure tends to change once in a while. I installed a regulator and keep it set at 50 PSI.

Check the pressure tank as labman adivsed, also check the temp of the water heater, make sure it is cutting off when it should and not overheating.

I recently installed a releif tank on my water heater, the box said that the 2 gallon one was good for my unit, a 50 gallon electric tank set to about 115 degrees with 50PSI incoming regulated pressure.

I have noticed that it seems once a pressure releif valve pops off a few times, it tends to get weak. Or at least it does for me. If it takes to dribbling or running water constantly, it too will need to be replaced.

My pressure relief valve on the hot water heater is releasing every couple of days. My tank is in an overflow pan. I get about an inch of water in the pan each time. We've replaced the hot water heater. Before that, we replaced the pressure relief valve (twice) on the old water heater. Problem seems to be getting worse since it's gotten colder. Plumbers have been scratching their heads on this one. We have 61 psi coming in from the street. I have an expansion pressure tank and it is installed on the outlet/system pipe approx. 3 feet from the tank. Its a gas heater, 8 months old. The expansion tank might be 8 to 10 years old. I purchased the home a year ago. My plumber thinks we need to start with a pressure regulator valve in the service line. Looking for suggestions???? thanks.
The expansion tank should be switched over to the inlet side of the tank, especially since, as you said, it is a newer tank which most likely has a check valve built into the inlet dialectric nipple.

Having it on the outlet side of the tank isn't doing your system a lick of good.

And Andrew Cocke is correct, once the T&P has popped off a few times, the spring inside is a blow-out just waiting to happen.

The expansion tank should be switched over to the inlet side of the tank, especially since, as you said, it is a newer tank which most likely has a check valve built into the inlet dialectric nipple.

Having it on the outlet side of the tank isn't doing your system a lick of good.

And Andrew Cocke is correct, once the T&P has popped off a few times, the spring inside is a blow-out just waiting to happen.

How is the expansion tank going to absorb the excess water from expansion I it is down stream of a check valve?

How is the expansion tank going to absorb the excess water from expansion i it is down stream of a check valve?

The expansion tank is intended to protect both sides (hot and cold) of the potable water system from thermal expansion.

Having the tank on the hot side, because of the direction of flow, protects only the hot side, while having it on the cold side protects both sides of the system.

The ball in the dialectic nipple is always in the open position when under NOP.