Water – Why does all of the house water stop working when the washer is in use

There are a few possible reasons:

• Some hot water recirculation systems use the cold water as a return. In these systems, warm water is returned in the cold water pipe until hot water reaches the the temperature valve that controls the recirculation. Or, perhaps the one-way valve near the pump is failing.

• Hot water pipes could be touching a cold water pipe (probably near the water heater). The two pipes touching would heat up the cold water pipe.

• Cold water pipes could be touching a ventilation duct. In the winter, the duct would be warm and would heat up the cold water.

• No heat trap in the water heater inlet. Hot water might flow up out of the water heater into the cold water pipes.

In the morning, try to feel which parts of the cold water pipe are hot, and that'll be your answer.

Another thing to check, but is likely unrelated, is the condition of a water expansion tank (generally mounted near the water heater) if you have one, or contemplate installing one if you do not (they're needed if you have a pressure reducing valve or a one-way valve in your water meter).

I suspect the sound is from the drain pipes, and comes from a leaky toilet, beacause that's the most common thing that has a stored reservoir of water to keep leaking after you shut off the main valve.

You might try leaving the main water valve shut off for several hours. If the sound eventually stops, go around and look in your toilets to see if any are now empty in the top tank (without you flushing) - or speed the process up and flush all the toilets after shutting off the main water valve and see if the sound then goes away shortly after that.

If you'd like to check on @Tester101's theory, try shutting off the main electric breaker and see if the sound stops or not.