AngryOldWhiteGuy wrote:
I have a Rheem 41V40, 50 gallon, gas hot water heater in our house - not
sure how long it has been here - the serial number is 0502 103535. I got in
the habit of turning the water off at the street when I leave for a trip any
longer than a few days - it's older house, and I felt that this would
minimize any water damage from a busted clothes washer line or broken water
heater.

I came home this evening after being gone for 5 days, turned the water back
on at the street, and the pressure relief valve for the hot water heater
tripped - it's got a pipe that vents the water to the outside of the house.
It stayed tripped for a few minutes (I was outside), until I got back inside
and I reset the tripped valve, and things seemed fine. I could hear the
tank heating, and I assumed that was because of the cold water that came
into the tank when it was venting.

There's a 25x25 inch catch pan under the water heater - I guess to catch any
water that leaks from the hot water heater and drain the leak to the outside
through a drain pipe running out of the back of the drain pan, which ties
into the pipe that the pressure relief valve uses to exit its water to the
outside - between where the drain pipe comes out of the catch pan and it
connects in to the pipe that services the pressure relief valve, there
appears to be some kind of valve or device in that section of pipe - it
looks like maybe it's supposed to prevent the pressure relief outflow water
from flowing back through the drain pipe into the drain pan, instead of
going outside where it's supposed to go - I'd never seen anything like that
before and I couldn't see it clearly.

Now I notice that the drain pan under the water heater has a small amount of
water in it - maybe a half of a small glass. The tank has refilled and
reheated - there's no water on the outside of the tank, no water dripping,
and no water near the pressure relief valve at the top of the tank.

Did this small amount of water in the drain pan most likely come back
through that valve in the drain pipe? Or is it most likely something else
and what's the fix?

Thanks very much for your guidance.




A couple of problems here,
One- Anytime an old P&T (pressure and tempurature) relief valve opens
it is apt to leak, you are supposed to test them every 6 months by
flipping the lever on them, but almost no one bothers to do that and
when they do it is apt to leak because it doesn't seal again.
Two- when you shut the water off you make a closed system and when the
tank comes on it will increase the pressure on the closed system, so
when you shut the water off, open a faucet somewhere so the pressure
won't build up and cause the P&T relief valve to open.