Odd hot water behavior

[DougSea]

I'm having a strange problem with my hot water and thought I'd throw the problem out there, see if this has happened to any of you and how you fixed it.

I spent the night on the hook Saturday and when I went to shower on Sunday I had alternating warm/cold water. I was only using the "hot" side of the shower valve so it's not a "mixing" issue. The periods of warm water corresponded to when the fresh water pump was running. When it stopped the water would go back to cold.

This is an all new behavior. My thoughts are to double check my connections to the water heater and the check valve. I did disconnect it when I winterized it but I'm fairly certain I hooked it back up correctly. Honestly, I can't think of why this is happening!

[jleonard]

There should/might be a check valve on the water heater inlet. Maybe that is sticking open?

[RobS]

It could be pulling cold water that is stagnant in another faucet's hot water feed that is "T"'d off the hot water outlet side of the water heater before the connection to the shower you are using. Such as a transom shower, cockpit sink, etc. If another hot faucet is not turned on the water in the hot line leading to it would be cold and if it reverse flows you'll feel it. Try opening all hot water faucets until the cold "stagnant" water is all out and you get hot flow from all faucets. Then use the shower and see if the cold spurts are gone.

[Halcyon]

Some Residential heaters have an internal tube that adds the cold water away from the hot out fitting to aid in mixing. I think it's called a dip tube. I know of one case where it broke off and the symptoms were similar to yours. I'm not sure if all heaters have them but it might be worth looking at an exploded parts view to see. Good luck !

[RobS]

Yes, good point, the the long dip tube allows the cold water to be added at the bottom of a water heater tank and the hot water pickup tube is short, thus pulling the water from the top. I just checked the manual for my Seaward heater for a dip tube. No tube shown, the cold supply simply dumps in at the threaded fitting. Doug, what make/model heater do you have?