Can someone please help me with this? I have a dedicated recirculation hot water system in my house. I know it is dedicated, because I have checked under the sinks for crossover valves, and there are none. The system works perfectly, except for one problem.

About a month ago, I suddenly started getting warm to very warm water (way past lukewarm) at all of the cold-water faucets. This was the FIRST time this ever happened in twelve years, so I knew something had changed.

I checked the pressure, which was very high (130 pounds), so obviously the PRV was bad, and I had it replaced. I thought that might be causing the trouble. Now the pressure is 55 pounds. But I still get warm water from the cold faucets!

If I turn the pump off, and wait a few hours, everything is near normal (much colder from cold faucet).

My floors are not hot, so I don't think there is any under-slab leak. Since turning the pump off seems to cure it, I am baffled.

The only other component I can see in the system is a check valve between the pump and the water heater. I can't see how this would affect anything.

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So what changed?

Thank you.



Edited 6 times.

The check is bad.

When you valve off the pump the issue disappears.


The check 'should' act as a shut off valve when the pump does not run else there is a cross connection with no 'flow'.



Edited 1 times.

Quote: Author: bernabeu (SC)
The check is bad.
When you valve off the pump the issue disappears.

Thank you. I should have mentioned that I did not operate the valve to the pump (but I will try that). I just unplugged the pump.

As far as I can tell, I do not have the red line shown in your diagram marked "A" that is attached to the cold water supply at the top. The line just goes from the pump straight into the bottom of the heater.

Do you mean the check is stuck open or stuck closed?

Thank you again.



Edited 1 times.

stuck open



Edited 1 times.

I am having a really hard time understanding this system.

My system looks exactly like this (comments in red are mine):

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I can't understand how hot water can *ever* get on the cold side. Even if the check valve is stuck open.

Thank you.

I really appreciate your help.



Edited 1 times.

'google' {gravity circulation}



the pump itself will RESTRICT, but not stop, it

the check stops it cold (pun intended)




(gravity circulation will occur with the 'b' connection since the water at the top of the tank is warmer than the bottom and induces a 'draft effect')

I'm pretty dumb about this stuff, but it drives me nuts if I can't figure it out after looking at it for two days. I couldn't sleep last night because of this, so I was up at 4AM checking and rechecking the leak indicator on the water meter.

Yes, I can see how the gravity circulation would happen if the check valve was open and the pump was off, but it seems it would just be circulating water from the tank back into the *hot* loop.

But how does *any* hot water *ever* get onto the *cold* side in a dedicated system? I can't see the connection between the hot water side and the cold side. I keep thinking I have some kind of a mental block on this.

It's not just a little bit warm. The cold supply is about 77 degrees, I have measured as much as 99 degrees coming out of the cold faucet.

Thanks.



Edited 1 times.

valve off the circ pump

if problem goes away you have confirmed a bad check

if problem persists you may have a crossover at a shower or possibly the washing machine or another single lever fixture

perhaps time for an actual onsite plumber