First post hoping for some help. I just installed a new 40 gal elec hot water tank with a new 2 gal expansion tank on the cold water side. After install, I went to the basement several times over the next 4 hrs to check for any leaks......none. Went to bed and when I got up this morning I went to the basement and found about a gal of water on the floor. I checked for leaks and everything was dry, even the pressure relief valve was not visually dripping at that time. Could it have leaked during the night? My water pressure was 45 pounds so I put that much air in the expansion tank so I know that part was right. Anything else it could be? I hung a small bucket below the prv to see if thats it for sure so hopefully I can pinpoint if that is the leak for sure. Any ideas would be greatly appreciated. Thanks.......Roger

the pressure in the thermal expansion tank should be set at 5 psi above the line pressure. If it is set at or below the line pressure, it will fill during normal operation and won't have the ability to absorb the expanding water as the tank water is being heated.

Just went and checked. Water pressure 45, expansion tank pressure 50. So far no leaks all day. Also, my water line coming in the house has a pressure regulator. Bout to drive me crazy....

If the tank is at normal working pressure, it will be "neutral". The air in the tank will balance out the water system, so it will have the maximum capacity.

I just now checked it again after several hrs of not running any water. Still dry however, feels like expansion tank is full and water pressure is now at 90 psi.?????

Just checked again about an hr later. Still dry but water pressure now at 120 psi.

IF the water heater has been operation during this time, then your expansion tank MAY be faulty or defective. If not then the problem is a failing pressure reducing valve, but there is no way for us to tell you which it is without being there to do our own testing.

The prv started leaking at 150 pounds. I then ran some water and it went right back down to 45 pounds. I'm going to change the water regulator tommorow. If that doesn't work I'll have to call a plumber out I guess.

It would be much cheaper and faster to simply change out the expansion tank first, keep the receipt so you can take it back if need be.

checked expansion tank. water running back out of it like it should. got someone coming over today to try to help. will keep posted. thanks for the posts.



Edited 1 times.

quote; "checked expansion tank. water running back out of it like it should"

What does that mean?



Edited 1 times.

when the pressure was so high it filled the expansion tank up with water. when i ran a fauset to relieve the pressure the water ran back out of the expansion tank.



Edited 1 times.

Do you have a check valve between your expansion tank and the hot water tank? The only thing that would make any sense here is that your expansion tank isn't actually doing its job. I find that more reasonable than a prv only working during banker's hours. Unless it is a union prv..



Edited 1 times.

Ok, sorry. THE PRV I keep talking about is actually the t&P valve. Hope this didn't confuse anybody.



Edited 1 times.

Fixed............new water flow valve.