PDA

View Full Version : Odd plumbing question



Larry Fox
01-09-2009, 4:08 PM
I have what I consider an odd plumbing question and I thought I would ask it here. I installed a new sink fawcet in my master bathroom. Nice set and I like it a lot except for one thing that I can't figure out.

When it sits for a while (an hour say) and you turn on the cold, everything is fine - comes out cold. Turn on the hot and it comes out hot. If you mix hot and cold to wash hands or something - everything is fine. If you turn it off and come back a few minutes later and turn on the cold, it comes out tepid. Not hot but definitely not cold either. Let it run on cold for a while (20 seconds) and it runs cold.

Supply lines are simple, 1/2" copper hot and cold.

Anyone have any ideas?

BTW: If you were going to suggest calling the plumber who installed it, he is tying the question. :D

Thanks in advance for your time.

Lee Schierer
01-09-2009, 4:23 PM
My daughter has a similar problem only her cold water starts out cold gets warm after 30-40 seconds and then gradually gets cold again even if no water has been run for a long time. At no point do the cold and hot lines meet except at the faucets. This happens summer or winter.

In your case the hot and cold lines may be close together somewhere near the faucet. Running the hot water heats the pipes and when the water is shut off the heat radiates into the cold line in a confined space (Like inside the wall) warming the water. 20 seconds of 1/2" line isn't much water through an aerator type faucet so this may only be 5-6 feet of pipe. If the tepid water is immediate it is located close to the faucet.

JohnT Fitzgerald
01-09-2009, 4:27 PM
Could also be the cold line is run somewhere near part of your heating system.

Sonny Edmonds
01-09-2009, 4:32 PM
Well now, your basic trouble is you have offended it.
See you got it all hot and bothered by calling it a fawcet.
Try going back and calling it a faucet, and maybe it will make up and be nice again. :rolleyes: :D

Udderwise, I think Lee might have it.
You didn't twist the excess line together under the sink, now did you? :o
I think maybe the mixer and internal piping may be the oddity you are experiancing here. It's new, so you have to learn it's little quirks.
If you run the cold for a few seconds I bet it gets cold and is fine. :cool:

Larry Fox
01-09-2009, 4:34 PM
Lee - I will check that, good idea.

John - good idea but not the case here. Listening to my wife it would be impossible because she would say we have no heat :) but the ducts are nowhere near where the water lines are.

Sonny - I really like your sense of humor and your posts are always amusing. Neither spelling nor typing are my strong points so I don't worry so much about them anymore. I may very well have the lines twisted, I will check.

Another important fact that I left out is that this just started after I installed the fawcet.

I do appreciate the time.

Sonny Edmonds
01-09-2009, 4:42 PM
I'm glad you took it as humor, Larry.
I think it may be just an oddity of the new fawcet, and really not a problem.
Just something new and different. ;)

Ken Becker
01-09-2009, 4:51 PM
install a check valve in the cold water supply line.

What is happening is the hot water is going into the cold supply line through the mixing valve when the faucet is off.

Kev Godwin
01-09-2009, 10:48 PM
Larry,
I agree with Ken Becker. I had the same thing happen when I installed a basin sink in the shop area next to my home office. I installed a check-valve to prevent the cross-mixing and it has been fine ever since.
Kev

Lee Schierer
01-12-2009, 12:45 PM
install a check valve in the cold water supply line.

What is happening is the hot water is going into the cold supply line through the mixing valve when the faucet is off.

I've heard people claim this but how can the water flow if the pressure is the same in both lines? A check valve wouldn't stop heat transfer due to conduction by the pipes or the water itself.

Chris Padilla
01-12-2009, 2:12 PM
Lee,

Just a guess but I think the hot water pressure is a ~*tad*~ higher than the cold-water supply because, well, it is hot! :)

Lee Schierer
01-12-2009, 4:25 PM
But since the hot water tank is connected to the same cold line coming in to the tank, the water pressure has to be the same. If the mixer were open between the lines byut closed off to the faucet, you might get some convection type of flow in the lines in which case a check valve would help, but I don't know if water actually behaves that way inside pipes. Hot air will rise, but does hot water?