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I have a utility sink in the basement. The previous owner had a habit of installing all the water fixtures backwards, so the "cold" line connected to hot and vice versa. Overtime, all the washers in the cold shut offs have started to fail. After replacing a few elsewhere, I'm stumped by the utility sink.

I have shutoff the hot water heater's hot line supplying the house. No other fixture can supply hot water, just a "shoosh" sound as I open it up.

However, at the utility sink, cold water continues to drain slowly, but never draining, from the faucet as I have the hot tap open wide and cold closed. I even closed the cold shutoff thinking the mixer in the faucet is failing to no avail.

It's run for over 30 minutes and drained several gallons of water, surely several times more than all the hot water piping in this house. This fixture is closest to the hot water heater at the bottom of the house.

Why do I get a continuous stream from the hot water only at this sink and nowhere else?

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  • Is the fact of the previous owner preferring the valves to be reversed from usual convention relevant to the fact of the basement utility sink dripping? I've not heard of a cold-side washer being damaged because it ended up controlling hot water flow, for instance. – Greg Hill Mar 26 at 21:34
  • @GregHill I understood hot water corrodes faster and that hot water fixtures, valves, etc. have different components that are slightly more resistant to corrosion. – AdamO Mar 29 at 17:16
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Depending on the size and length of the piping throughout the house it's not unreasonable to estimate that there might be two gallons or more water contained in just the hot water piping. In the case of copper tubing, 50 feet of 3/4" contains 1.1 gal while 80 feet of 1/2" contains another 0.9 gal. It's relatively easy to consume that much piping especially in a two-story house or multi-bath house.

After the hot piping is drained down (whatever its volume may be), if water continues to exit from that basement-level faucet, it is being replenished from somewhere. Some valve is leaking water from the cold system into the hot system. Two possibilities come to mind:

  1. The shutoff at the water heater leaks, allowing new water to flow through the heater tank to the faucet.
  2. A mixing valve somewhere in the house is allowing water to leak from the cold side to the hot side, but not leaking to the faucet's normal output.

You mentioned testing whether this faucet's mixer leaks by turning off its cold supply. Try turning off all the cold supplies at all the other single-handle faucets in the house too. If the drip stops, then turn those supplies back on one at a time to find one that leaks. There could even be more than one that leaks. In the event that you have one or more single-handle faucets for a bathtub filler or shower (where there's no secondary shutoff valve as there would be under a sink) you might not be able to prove whether or not one of them has such a cross-supply leak.

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    This is a good answer that includes good troubleshooting steps. I would recommend starting with the most likely (see Occam's Razor), which in my opinion is that the valve which directly feeds water into the hot water system, at the water heater, is leaking-by. – Jimmy Fix-it Mar 27 at 0:09
  • Open the higher hot taps AND this hot tap to let the water in the pipes flow easily, rather than dribble out. If you pay attention, you might gain an inkling as to why vents are so important in drains. The "shoosh" sound is air heading into the pipe to let water drain at the low point. – Ecnerwal Mar 27 at 0:32
  • Ahh, @Ecnerwal makes a good point that we all missed, the system could be vapor-locked. You always need a high-point vent... – Jimmy Fix-it Mar 27 at 0:59

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