I have a very simple house. 2 bed, one bath, laundry. It had been flipped in 2012 and then I bought it last year. New furnace, new water heater, new everything including nice PEX plumbing everywhere.
I'm re-doing the kitchen... well, countertops, sink, and faucet and adding a couple cabinets. I'm also adding a dishwasher so I had to replace the sink valve with a dual-outlet valve on the hot side.
So I went to the basement and turned off the inlet valve on the top of the water heater, stuffed the faucet hose in the drain pipe, and opened the hot sink valve to relieve the pressure. To my surprise, I got a steady supply of cold water. I went to the basement while it was running and verified that no water was coming out of the water heater. (using sound and feeling the pex for vibes and heat) I traced the pipes and it's stupid simple. The line comes out of the hot tank, across the ceiling, then up to the sink. It tees off one way for the laundry and tees off the other way for the bathroom.
I was obviously able to do the valve by shutting off the house valve at the meter, but why am I getting cold water out of that hose when I shut off the water heater inlet valve? I was getting hot water at all of the sources before I discovered this. Never had a problem washing dishes or showering. What am I missing?
One of your faucets is crossing over? Mine will do this with both sides open, but I'm not sure of the mechanics.
None of the other faucets were on. The main for the house was still on so I would have heard the water. I have a theory though... laundry spiggot. It's one of those that has one handle for both taps. I'll bet it was coming through there.
Like this:
Makes me wonder how much flows through there during normal operation. Am I mixing hot and cold all the time? I'll have to do an experiment. I can test the hot water's temp at the sink with that valve open and closed and see if there is a difference.
Both of those valves in that laundry faucet are separate. Water can't cross over because there's no passage between them.
Single-lever faucets can fail and pass water from hot to cold and vice-versa if an o-ring in the cartridge has let go. Maybe have a look there.
Showers have scald protection in them. The way I understand it is that it balances the pressure to what ever you are setting it to. I wonder if cutting all the hot water pressure resulted in the cold water being able to effectively bypass the valve and go back in the hot side
I tried putting a screwdriver to my ear on faucets to see where it was making noise and I didn't seem to find one that was louder than another. I didn't check inside the washing machine though. If the valve in there has a crossover, it could be the culprit.
