plumber question

[rjet]

I have a marathon water heater that is 4 years old. Noticed water in the garage (quite a bit) and it was coming from the water heater. I took the wet-vac and got all the water out of the pan to see if the water heater was leaking or if the pressure relief valve went off. So far no water in the pan.
Question is what would cause the pressure relief valve to go off?

[TXBlkCld]

Either the pressure in the heater got over 150psi, the water got over 210* or the T&P valve just needs to be replaced. More than likely the T&P is just bad and the spring is weak. It's pretty common for them to go out. You should pop-test (trip the lever for just a second) them every 6 months to make sure it shuts off all of the way. If it doesn't, then replace it. The pop-test is the best way to make sure the T&P valve is working properly. If it fails to work properly, it could cause the water heater to explode and literally level your house and possibly kill you and your loved ones. Not a joke. That's fact, not fiction!! Exploding water heaters have levelled entire schools in Oklahoma.

[froghunter]

3 things. too much pressure, too much heat, bad valve. Not sure about marathon, but alot of instantanious heaters have vent pipe that condensate in cold weater. if there is a small nipple on the collar where the vent pipes connect or on the vents themselves add a peice of tubing to it and run it outside. Also the T&P should have a 3/4 pipe attatched to it and be ran to the OUTSIDE of your house. If there is a leak water will keep showing up in the pan. occasional water would be from the T&P(if it is not ran outside) or condensate.

[rjet]

I popped the valve after I wet-vac-d the pan and it released and stopped fine. Will monitor it for a while and replace the valve if it acts up again. Kind of weird how it just happened after only 4 years. Drain goes into the garage which is sloped down to drain out the front. Not crazy about that setup and dont know why they didnt run the relief outside.
Thanks for the input.