Cold tap runs hot-why???

Recently moved into a limestone house we’d renovated in Crown Heights. Discovered this problem–the cold tap in the 2nd floor bathroom sink runs hot. If you let it run for perhaps a minute it goes cold. What could be causing this? We had some plumbing redone in the kitchen and basement but the bathroom seemed OK. We need a new sink so I’m hoping it’s something to do with the water pipe to the sink. Any help/suggestions/solutions would be much appreciated.

yaldwyn

in Plumbers and Plumbing 13 years and 8 months ago

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Master Plvmber | 13 years and 8 months ago

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It depends. If you are using a retro-fit recirc pump that dumps hot water into the cold line that crosses branch lines to fixtures, then yes, you will have warmer cold water than usual for a few seconds. A system piped with no recirc or a proper recirc line that terminates directly to the water-heating source, then things will work normally with no crossover.

nyc_sport | 13 years and 8 months ago

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I actually thought that this was “normal” when a recirculation pump is used because hot water is returned via the cold line, no??

Master Plvmber | 13 years and 8 months ago

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Something upstream of the sink’s water connection is cross-feeding hot water into the cold water piping. We call that a cross connection. 8 out of 10 times it’s the shower faucet with a stuck-open or missing check valve. The other common problem is when construction is too tight, heat from the hot water pipe can’t get out of the walls and it warms the cold water pipe. This is especially common where hot water recirculation is used. 
I know a lot about this kind of thing:

http://brownstoner.staging.wpengine.com/gatewayplumbing