Hot water backing up into the cold pipes

[Tom7227]

I put in a new gas hot water heater a couple months ago. On a second floor faucet I got warm water for 20-30 seconds, at least it seemed that long. A person at FF told me I didn't need a check valve although I had put one in the old heater. A few weeks ago Rich Trethewy on TOH talked about the hot water backing up into the cold pipes. He replaced a valve on a shower head. I think he said that the backup had to happen to relieve the pressure.

There's nothing wrong with the new rig. It is a high end rig and I doubt they forgot the dip tube or whatever sort of manufacturing gremlin could cause this.

I don't understand why you would want the hot water backing up. I also am not enamored with the idea of having to take apart the line from the water heater and putting one in. What do you folks have to say about this?

Thanks for your time.

Tom

[CAMAN]

Here's the episode you're talking about. I thought about this episode the moment I read the title.

I'd do what Rich did and inspect the nearest shower valve, you probably have a broken mixer valve. You don't want water moving backwards at all.

[Tom7227]

I replaced both shower valves a year ago. Brand new kitchen faucet. Why would it only start when the new water heater was installed? Without a check valve on the cold line.

[CAMAN]

Weird things can pop up after doing something you think is totally unrelated, especially if you turn the main water valve back on too fast and it surges.

Is this a single or dual handle faucet?

[Redlantern]

If you have a problem with a faucet or shower valve, a check valve at the water heater won't do a bit of good to solve this problem. More than likely, you have a faucet or shower valve that's allowing the two to mix. I might be mistaken but didn't you do some work on a shower valve somewhat recently? That's the first place I'd look. Probably some debris stuck in the cartridge allowing the hot and cold to mix.

[WallEYES]

If you have single lever faucets, even if they are new, change out the cartridges. Do not install a check valve you might end up tripping your temp/pressure relief valve on the water heater

[Archerysniper]

If you have a problem with a faucet or shower valve, a check valve at the water heater won't do a bit of good to solve this problem. More than likely, you have a faucet or shower valve that's allowing the two to mix. I might be mistaken but didn't you do some work on a shower valve somewhat recently? That's the first place I'd look. Probably some debris stuck in the cartridge allowing the hot and cold to mix.

+1,000