I have a problem where cold water comes out of the hot water line in my bathroom faucet when I turn on the shower. If I turn on the kitchen faucet then the shower gets colder. If I have all three running then the faucet has cold water in the hot line but the shower and kitchen faucet are okay. I do have a recirculation line in the plumbing. The issue noted here will happen when the recirc pump is turned off. Once I turn on the recir pump then there is no issue. My goal is not to have to use the recir pump but still be able to run the bathroom faucet and shower at the same time. Interested to hear if anyone has seen something similar to this issue and any recommendations on troubleshooting/fix.

Thanks

It sounds like you have a bad check valve, or don't have one at all. You are getting cool/cold water from the return side of the system. if it connects back to the cold water line right before the hot water tank's input side then it needs a working check valve

thanks for the feedback. Yes, there is a check valve installed in the return line between the recirc pump and the input to the water heater where it joins the cold line. This is a fairly new heating/plumbing system (~1.5 yrs). So it's possible that this check valve has failed?
Also, wouldn't I get cold water in this line when the recirc pump is off as well as all faucets/shower. So basically the cold water would flow back into the recirc line. But in this case the return line remains hot when in this condition. Yes, once I run the faucet/shower then this return line goes cold.

while the pump is off and a check valve is bad, hot water from the tank, and cool/cold comes from the end of the return line backwards to the fixture where they mix and the result is colder water than what should be there

okay, thanks for the feedback. I will look into the check valve. Apart from the problem I have outlined is there any other downside to this (leaving the suspected check valve in place). Just trying to see what urgency I need to put into fixing this.

Not that urgent if the pump is on, but the problem won't stop until addressed. you can try smacking the check valve a few times with something to get some vibration in it; If the problem is just that it is stuck for some reason, that may cause the internal flap to break free and start operating again. Just don't go all Chuck Norris on it and bust your plumbing. A couple good raps with a large pair of pliers or a crescent wrench handle should be enough; if it works, awesome, if not, then replace.

thanks again. Will try to free up the check valve as you noted. Otherwise time for a replacement.



Edited 1 times.

I replaced the check valve and it is now working. The old valve was stuck. Thanks again