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?
Best Answer
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:
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.