copper pipes over old wiring

I just finished sweating a bunch of copper pipes for our bathroom remodel. They are under the floor about 2 inches above some old knob & tube wiring. My wife came to admire my work and said "is that ok to have them so close?" I said it was fine and she then said "won't they drip on the wires?" and I admitted that I didn't know.

Does condensation form on copper pipes? I know it happens on refrigerant lines but I didn't really think it was a problem with hot & cold water. Is it?

Under the right conditions (high humidity and cold water in the piping) copper piping will sweat just like any other material. Get some of the foam pipe insulation and slip on the cold water lines and that will alleviate the problem.

While you're at it insulate the hot water lines too. The thicker the insulation the better. Don't forget to close the seam on the foam.

If you had the walls open that much, you probably should have replace the knob and tube wiring as well.

Code dictates that you can't do that unless you would have access to Junction boxes where the splices would be that are inside the living areas...you can't bury a splice in a wall or floor....

Cass said:

You can't do that unless you would have access to Junction boxes where the splices would be that are inside the living areas...you can't bury a splice in a wall or floor....

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I agree with that, but I'd try my best to replace what I could if I was gonna be tearing out drywall anyway.

pipes

Pipes inside closed spaces do not have condensation unless there is a way for the humid air go get into them. And the pipes would normally only be cold enough to cause it if there were a leaking faucet or other problem keeping the water moving through the pipe.

I would replace the knob and tube but unfortunately the house is 90 years old and the knob & tube is everywhere. The wiring exposed in the bathroom is maybe 5% of what's in the house and to get to a switch or junction box would mean tearing down the first floor ceiling.