Every year when we go on vacation I turn the water off to the house. Last year we noticed that the carpet in the basement which is next to the closet that houses the hot water heater was damp after returning home and turning the water back on. We did not notice any water on the floor next to the hot water heater at this time. This year after turning the water back on I checked the hot water heater and found that water had "sprayed" out of the top of the unit due to the fact the top of the water heater was covered with water as well as the back of the dry wall in the closet. The water also ran down the side of the water heater and ran under the 2X4 to the next room which cause the caperpet to be wet again. There was a puddle around the water heater but it was dry under the pressure release tube. I have never noticed any leaking around the unit which is about 4 years old and it is bone dry now. Any ideas on what to check for would be appreciated.

When the water heater starts heating the cold water there must be room for expansion. Some homes have an expansion tank right next to the heater. Most often the expanding water can push backwards through the cold incoming water line but not in all situations. I would check my water pressure to see if its about 45 psi. If your pressure is fine now I'm thinking the expansion popped your T&P valve at the top of the tank, it should open at either due top high pressure of high temp. Try opening your hot water faucet just a trickle next time you turn the heater back on after sitting cold, just for the time it takes to heat the tank. You could also just install an expansion tank.

Do you have a sprinkler system, a check valve or a backflow preventer installed? Let me know. Tom

Thanks for your help and I will try opening a faucet next time. I do not have a sprinkler system.