I'm totally re-doing my bathroom and shower. I tore out the old shower
months ago, re-routed the plumbing, and capped off the pipes. At this
am ready to install my new shower mixing valve but I don't know
which pipe is
hot and which is cold.
Are there any tricks to identify which is which short of uncapping the
letting the water fly??
Turn off the water to the water heater. Turn off the main water
supply to the house. Uncap one pipe. Turn on the house water
slightly. If water comes out the pipe, that is the cold. If not, it is
You just look where you wrote on them with the magic marker. :)
Run the hot water in the nearest room that has hot water. It may warm the
pipe enough that you can feel a difference between the two. If you followed
normal conventions, the pipe on the left facing the point of use is the hot.
Thanks a lot for all the great tips!
I ran the hot water tap closest to the pipe for awhile to get it nice
I then turned off the main water line and drained the pipes
(to get the layer of
room temperature water out of the pipes). I then
turned it pack on,
theoretically filling the pipe with fresh hot
It worked, I was able to feel the temperature difference in the two
Now I just have to install the valve, hang the sheetrock, buy the
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