Intermittent Cross Connect?

[SAS]

Occasionally, we have warm water coming out of all the cold water faucets. I have checked the pipes by the recirculation system, but that does not seem to the culprit. The pump is connected at the top of the water heater and there is a check valve preventing hot water from flowing up into the cold water feed. Also, the recirculation pump runs continuously and the probelm is intermittent. The last time it occurred I noticed that it was right after the washing machine had run. Is it possible for the hot to flow into the cold from the washing machine mixing valve? If not, what else would explain an intermittent flow of hot water into the cold water line?

 

[Smooky]

....there is a check valve preventing hot water from flowing up.....

What type of check valve? What did you do to check the pipes by the recirculation system?

 

[Sponsor]

 

[Jadnashua]

WHen the WM is set to warm and filling, with the recirculating pump, it could allow some mixing in the lines as well. Probably more likely is a single handle faucet somewhere. If it is closed when turned all the way to hot or cold, it probably couldn't cross-over, but anywhere in the middle, at least on some designs, it could leak from one side to the other. If you have individual shutoffs, try turning one supply off (won't work with a shower valve with pressure-balance functions, though) and see if you can isolate one of them that is crossing over.

 

[SAS]

WHen the WM is set to warm and filling, with the recirculating pump, it could allow some mixing in the lines as well. Probably more likely is a single handle faucet somewhere. If it is closed when turned all the way to hot or cold, it probably couldn't cross-over, but anywhere in the middle, at least on some designs, it could leak from one side to the other. If you have individual shutoffs, try turning one supply off (won't work with a shower valve with pressure-balance functions, though) and see if you can isolate one of them that is crossing over.

The reason I'm guessing the washing machine is that the problem is intermittent. From what I understand about cross connections with single handle faucets and shower controls, the problems are consistent not intermittent. I was wondering if it was possible for the washing machine to allow hot water to backflow into the cold while it's running. It sounds like that might be a possibility, so I'll test it.

Thanks.

 

[SAS]

What type of check valve? What did you do to check the pipes by the recirculation system?

I'm not sure about the type of check valve, but the cold water feed above the check valve stays cold while the pipe below it is warm.

 

[Reach4]

Consider feeling cold water lines at the faucets when the problem occurs. It seems to me that the warmest cold line will be near the cross connect.

 

[Jadnashua]

Some single handle faucets allow you to turn them off when the control is fully one way or the other. Most Delta faucets, force the handle to the middle position (but aren't normally a source of a crossover). If the faucet is fully one way or the other, verses somewhere in the middle, it would shut off the cross-over, verses, if it were not fully one way or the other, mixed.

 

[hj]

You have one of several "retro fit" circulation systems. They CAN cause momentary hot water in the cold side if the thermostatic, (not check), valve malfunctions. The washer lines merge inside the machine's tub and there is no way they can "cross feed" the water. There are so many possibilities that someone would have to be there at the time to check where it is happening.

 

[SAS]

You have one of several "retro fit" circulation systems. They CAN cause momentary hot water in the cold side if the thermostatic, (not check), valve malfunctions. The washer lines merge inside the machine's tub and there is no way they can "cross feed" the water. There are so many possibilities that someone would have to be there at the time to check where it is happening.

I don't believe that the recirculation is a retro fit system at all. It is a full loop from the hot water fixtures to the hot water heater. It runs continuously and does not have a thermostatic valve. I really don't see how it could be the culprit.

 

[hj]

In that case, it would not be, but your description of how it is connected was sort of IFFY. The check valve SHOULD be installed to prevent the cold water from flowing INTO the circulation line, not the other way that you describe it.

 

[SAS]

In that case, it would not be, but your description of how it is connected was sort of IFFY. The check valve SHOULD be installed to prevent the cold water from flowing INTO the circulation line, not the other way that you describe it.

There are actually two check valves: one to prevent cold water from flowing into the recirculation line and one to prevent hot water from flowing back up the cold water feed (the recirculation line is feeding into a tee at the top of the hot water heater).