I just had my gas water heater replaced. Ever since the replacement, when I turn on the cold tap on any faucet in my house, it runs cold for about 15 seconds, then hot water starts coming out. The hot water keeps getting hotter and runs for about 30 seconds, then cools off and goes back to cold. This happens on every faucet in my house and has been happening for the past two weeks since the new water heater was installed. I called the plumbing company that installed it and they are stumped. I cannot live like this, my daughter has almost scaulded herself several times. Can you please help?

Sounds like the dip tube was damaged during installation.

Bob is right growler.. think we misread this one!

Hey, here is what I want you to do:

Wondering if you have a faucet with 2 separate handles...1 for cold, 1 for hot.

I want you to turn on the cold water only at this faucet and see if it hot water shows up at that cold faucet. T est for a few minutes.. and test at ALL faucets that have 2 handles on them... test each cold (hot handle OFF) and see if any hot shows up.

If it doesn't then I think we have a defective mixing valve somewhere in the home. This could be a mixing valve coming out of the water heater (unlikely though as most water heater installations don't include these) or at the shower or at any single handle faucet in the house.

It may be that when water heater was installed some sediment got disturbed and somehow damaged the mixing valve cartridge of a valve... that should be the only link between the water heater and this problem.

If defective mixing valve (as confirmed by above) then we need to find the defective mixing valve and fix it.

Start by turning the cold water shutoff under your kitchen sink OFF (as long as single handle faucet). Then try to use the hot AND cold water. If water runs out when rotate handle to cold, then you have a defective cartridge at the kitchen sink faucet and will need to replace the cartridge.

If not kitchen sink faucet, can repeat this same test at the other single handle faucets (except the shower valves) and see if can confirm which mixing valve is defective.

Shower valves are tougher to confirm when hot coming out of cold (they are pressure balanced so won't work if hot OR cold shut off)

Anyway...call your plumber and see what he thinks of this idea....really only thing that makes sense. Hopefully he can pop out and find defective mixing valve and ix this right up for you... ;)

Let us know what you think... Mark

The Link below may help you
How a water heater dip tube works and what it looks like.

Did I read something wrong, this is the cold faucet, not the hot. I am having trouble picturing how the cold faucet would be affected by the heater dip tube. I'm open to any explanations.

NOPE Bob..you read it right. I think growler misread it and I just barely read it and having seen this issue so many times for the HOT water... just assumed it was the dip tube!

I rewrote my post so gives solution I think is correct!

Thanks for heads up! Mark

Is there a recirculating pump on the system? If so it could be a checkvalve problem.

Hey SP.. I was thinking same thing last night.

Imagine if his plumbers missed that one though?

We'll have to wait and see... ;)

Thank you all for your help!

Guess what it was! Ever heard of an overflow tank? Well, it was installed incorrectly on the hot water pipe instead of the cold water pipe. The county came out to inspect and found the error. So, the plumbing company had to come out and correct and that was the issue.

I appreciate all of your help! And for massplumber2008, a defective mixing valve was the plumbers first thought also until they corrected the overflow tank and it no longer happened. They were not very open to the idea that it was the overflow tank being installed incorrectly that was causing the problem.

You all are awesome and I appreciate all of your suggestions because I couldn't have gotten through this without you all!

Hey that 's terrific... glad this is resolved... ;)

I have heard of an overflow tank... not common here in New England, USA. Where are you from?

Thanks for the update!

Hi!

I am in St. Louis, MO... it's something fairly new on the code books. Was just required starting a year ago.

Thanks again!

If you can access this code I think several of us would be interested in reading it. How about a copy or a link.