Water heater problem

Wayco Wayne_2

I just helped out a neighbor by replacing their water heater that started leaking. Not a big deal. Just a 50 gallon nat gas with draft diverter at the top. Connect cold pipe to cold pipe. Hot to hot. Run new flu pipe. I even added an expansion tank. What could be more simple? Now a week later they are saying they are experiencing  hot water coming out of the cold water spigot s for a short while. I went in to the kitchen sink and turned on the cold water after running about 10 seconds, sure enough, about 10 seconds of hot water followed by cold. What the heck! What could be happening? 

Tom Blackwell_2

Pressure drop

The domestic water pressure is probably falling when water is released, causing the contents of the expansion tank to backflow through the water heater and back up the cold water inlet. You could install a check valve in the cold feed to the water heater to stop this.

kcopp

could .................

the dip tube have been damaged or dislodged ?

MNPLUMBER

expansion tank

It's the expansion tank as Tom said. Curious where you installed the tank and on which line?

STEVE PAUL_3

NO GOOD DEED GOES UNPUNISHED

The problem is due to the expansion tank. You were Mr. nice  and added an expansion tank. Was it necessary? Were there expansion problems? If the old heater functioned without an expansion tank without the T&P valve relieving or dripping, I would go back and remove the tank and plug the connection.

Don't you hate being the good guy and being bitten on the butt?

Wayco Wayne_2

I don't

Think it needed an expansion tank. I'll take it off and see if the problem goes away. they say don't help friends and neighbors but I can't help myself. they're such nice folks.

Wayco Wayne_2

I don't

Think it needed an expansion tank. I'll take it off and see if the problem goes away. they say don't help friends and neighbors but I can't help myself. they're such nice folks.