Cold water in hot water line

I replaced my hot water heater this weekend, and all went well outside of the usual leaks and kinked hoses. One thing I noticed, however, is that water would flow out from the hot water pipes in the wall unless the water to the whole house was off. I thought it was just water in the pipes, but it clearly stopped when the water to the house was off. Another indicator of the same thing (which I didn't pay attention to at the time) was that the kitchen sink still runs in the hot position even when the hot water is completely disconnected. At first I thought it was a sloppy valve in the kitchen faucet, but I'm certain it's all the same thing now.

So, any ideas how this could be happening? It's not full flow, but a steady stream, more than a leak. All I can think of hooked to this is two bathrooms, kitchen sink, washing machine and dishwasher. Is it possible the washing machine has a pre-mixer that is connecting hot to cold all the time?

A more likely location for the cross-over is at one of the shower or sink single handle valves. If you have shutoffs for each faucet, turn them off one at a time until you find the offending one. Some brands of shower valves are notorious for crossover when they start to wear out. What brand are the valves? This would not apply if they are two handle valves with individual hot/cold volume control - only single handle ones where the internal guts from the single handle perform that task (and then, only some brands/designs).

Thanks. I think my newer ones are Moen from Home Depot or Lowes, the rest are 70's vintage originals. I'll try shutting them off one at a time to see what I can find. Does it hurt anything?

If you have a crossover, it only gets worse, so you'll eventually have lukewarm water everywhere. If the water gets too hot, it might damage the toilet or melt the wax seal. Other than that, no, it doesn't hurt anything except your wallet, as your water heater will work harder since even when drawing cold, you're also drawing some hot.

quote; and all went well outside of the usual leaks and kinked hoses.

LEAKS and KINKED hoses are NOT "usual" when replacing a water heater. Worn out Moen valves are the most common cause of your symptoms, and there is NOT likely to be any way you can "shut them off".

jadnashua said:

If you have a crossover, it only gets worse, so you'll eventually have lukewarm water everywhere. If the water gets too hot, it might damage the toilet or melt the wax seal. Other than that, no, it doesn't hurt anything except your wallet, as your water heater will work harder since even when drawing cold, you're also drawing some hot.

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I THINK he was saying he gets cold water on the hot faucets, even when the water heater is removed. That is of coursed caused by something crossing over from the cold side. Assuming he does not have a recirc pump, then when the water heater is fully restored, the crossover mode will still be cold INTO the hot side. This is due to the slight ΔP caused by the water flowing through the wh.

hj said:

quote; and all went well outside of the usual leaks and kinked hoses.

LEAKS and KINKED hoses are NOT "usual" when replacing a water heater.

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Not sure what you mean. I just mean that it seems like every time I replace something, the fittings are in a new place. In this instance the inlets/outlets were closer, making it impossible to make the connection without kinking the hose. So I had to buy different hose to make the connection. Then the connection at the wall leaked and required more teflon tape... and one solder connection was bad and needed to be redone. Standard stuff for me, I'm no plumber.

Whenever you replace something with flexible supply lines, you should replace the lines! And, if these thread on, depending on the type, they may leak if you use tape...some are designed with internal seals, some need tape, but using tape on one that was designed to seal without it WILL cause it to leak.

quote; In this instance the inlets/outlets were closer, making it impossible to make the connection without kinking the hose.

ALL conventional water heaters have the inlet and outlet in EXACTLY the same place, other than allowing for different diameter water heaters. If the crossover is due to a failing Moen valve, or similar, it will NOT occur when the heater is functional, UNLESS something causes a major, sustained, drop in the hot water pressure, which usually does NOT happen in a single family residence.