warm water from the cold faucet?

[bigelee]

I am renovating an apartment on the top floor of a four story house. I installed a single handle shower mixer and a separate tub (which has a two handle and spout layout). I turned on the water to the apartment and everything seemed fine, but now there is warm water in the cold line in all of the apartments. Does this mean that the shower body is bad? did I connect it wrong? is there a backflow valve that I missed or something? Or could this be something worse and there are crossed hot and cold lines somewhere? What do I do to fix this-help!!

[faucetman886]

Is the water in the toilet tank when it refills also warm? Is there a central water heater for all of the apartments? If yes to both you could have a over heating HW heater that the T&P valve isnt functioning. I have run across this 3 times in the last 3 weeks on various forums. Potentially very dangerous.

[jadnashua]

Some single-handle valves can fail and provide a cross-over. Try (if you can) turning the handle all the way to one side while off and see if it makes any difference.

[bigelee]

Thanks for the responses- the shower mixer in the new apartment is a Kohler, so I called them and they are sending me a new valve. I will replace it and post if that was the problem- let's hope so!

[bigelee]

I replaced the valve in the shower- single handle mixer- I assumed this was where the lines were crossing, but no go. The water coming into the toilet is fluctuating between hot, warm and cold. Could it be that the hot water heater is too hot and is somehow pushing the hot water through the valve anyway? HELP!!!

[FloridaOrange]

Is there a mixing valve somewhere in the line?

[bigelee]

there is the mixer for the shower, but it is brand new AND I replaced the valve with out solving the problem. I am now turning the temp way down on the hot water heater (it was all the way up) to see it the hot water pressure was too high and was forcing its way into the cold (I assume through the shower mixer). The tub has two handles which are off, so that isn't it, right?

[Fuzzy2]

OK, I finally had to come out of lurk mode to reply to this one.

Forty years ago, when I was in school in Cambridge MA, I lived in a top-floor
apartment in a four story building which was some ninety years old at the time
and I believe is still standing.

Every morning we were treated to scalding hot water from the cold water faucet in the kitchen. I eventually worked out (by inspection) what was going on: the hot water heater was in the basement with a recirculation pump, and both the hot and cold water pipes were routed up through an interior light/air shaft to the attic of the building and then down to the apartments on each floor. But the pipes, of course, were galvanized, and held by common metal clamps all the way up and across the attic, so the recirculating hot water warmed the standing cold water in the pipes to the kitchen which weren't used overnight. The bathroom fixtures were less susceptible, because they were in more use during the night.