Hot water getting into cold lines - bad valve?

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PeteD

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I did a little searching already. Situation: There is an on demand hot water boiler with recirc lines and pump on aquastat (at the boiler) - professionally installed. Lines at boiler stay hot and cold like they should be. I believe the issue is one of the valves on a fixture is leaking the hot over to the cold side. There are no crossed pipes as hot is hot and cold is cold after running faucets for a bit.

I am going to test all of the sinks and the washing machine by shutting off the hot side and seeing what happens.

The showers are Symmons Oxford series (looks like these have temptrol guts?) and there is a Moen single handle kitchen faucet. The washing machine is a new high efficiency Electrolux. Bath sinks are all two handle.

Hot and cold seats in the two showers have already replaced with no change.

Are showers the most likely culprit? Is the cartridge the likely problem there?

Any other words of advice?

Thanks for a great forum.
 

Terry

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Sometimes it can be a shower cartridge crossover,
or I have also seen shower heads with shutoffs. If the shower valve is left open and the shower head is closed, it forces water through.
 

PeteD

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Sometimes it can be a shower cartridge crossover,
or I have also seen shower heads with shutoffs. If the shower valve is left open and the shower head is closed, it forces water through.
Thanks. There are not shutoffs on the shower heads.
 

Reach4

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Try feeling the cold lines at the fixtures. It seems to me that the hottest one would be the leaker.
 

PeteD

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When and where do you notice the problem?
At every cold water faucet. Goes cold after less than a minute. The time to warm water varies with location. I will do some more testing, but I think it is the showers or the kitchen sink.
 

Smooky

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Is there a seperate line for the recirculating hot water or is it returned in the cold water line? If the is a seperate line going back to the hot water heater, does it tie into the cold water line?
 

PeteD

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Is there a seperate line for the recirculating hot water or is it returned in the cold water line? If the is a seperate line going back to the hot water heater, does it tie into the cold water line?
Two separate lines (one from each bath) back to the on demand boiler. Boiler has isolation valves and cold lines are separate.
 
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