Insulation foam on copper pipes

Yesterday I noticed that paint was peeling in my kitchen downstairs. I took a good section of it off and noticed that the drywall was moist and dark in color due to humidity. I decided to replace the drywall but when I took it off ants were swarming underneath. There must have been 1000's inside the wall because they loved the humidity. I removed them and the insulation inside the wall. There are also three copper pipes which run vertically behind the drywall I removed. I noticed that the two hot water pipes which were insulated with foam were wet and that's where the water was coming from. I removed the foam insulation and one was completely wet on the inside while the other was only partially wet. I checked the pipes for leaks but did not notice any while it was uncovered. I bought new insulaiton for the pipes and covered them both. Within a timespan of 2 minutes the one of the hot water pipes once again contained condensaiton after it was covered. Is it normal for copper pipes to sweat, however did this not occur while the pipe was not covered with the foam insualtion. Can I patch up a new piece of drywall without insulating the pipes or what is going on. As far as I know, the insulation is only to keep the pipes insualted for the hot water. I live in CA so I'm wondering if I should not insulate them if years from now it will be humidity inside the wall again. Thank you in advance for your help and advice.
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I've never seen condensation on a hot water pipe. Are you sure of this? If the pipe is colder than the dewpoint of the ambient air, you get condensation. That is virtually impossible with a pipe that has hot water running it it. Don't seal up that wall until you figure out what the real problem is.
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You have pin hole leaks.
Find and stop the leak then repair the damage.
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Might be Stress Corrosion Cracking. The insulation blowing agent used in some rubber pipe insulations is corrosive to copper tubing when wet. Usually just a problem with refrigeration piping, I never heard of it on hot water lines. At any rate, your tubing in the wall needs replaced.
Stretch
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I didn't think of it until another poster brought up pinholes. In some areas, the water is very corrosive to copper pipes. Perfect area to use PEX if that is the case.
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The funny thing about this is that the leaking or sweating of the pipes only occurs when the foam insulaiton is on the pipe. The foam has been all day today and no humidity is on the pipe. It is strange. Should I patch up without the foam and why is this occuring.
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I meant to say that the foam has been OFF all day today and there is no humidity on the pipe. Thanks again guys!
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I suspect the hot water pipe is leaking. Water vapor will seek out cooler surfaces to condense.

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Thanks guys, tomorrow I am calling a plumber to look into this. Like I have been saying, the humidity only occurs when the insulation foam is on the pipe. This is really strange!
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Might be evaporating when the foam is off?
Foam, like diapers, tends to trap moisture.
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Christopher A. Young
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What is strange is that you keep calling it "humidity", when it's clearly not.
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snipped-for-privacy@gmail.com says...

It's a very small leak, spreading water onto a hot pipe. When the surface of the pipe is exposed, the heat makes the water evaporate quickly. When the pipe is covered, the water can't evaporate so the pipe appears wet.
I expect if you took a very close look at the pipe while it was un- wrapped you would find one small area that stays damp, right at the leak. (Of course, the way things work, the leak is on the back side of a soldered joint so you can't see it without sticking a mirror in behind the pipe....)
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Personnally I'd try and solve the wet hot pipe problem first.
Sorry to be ageuementative but this is illogcal - condesation forms on cold surfaces not the hot (living in the UK we know this, we have a lot of cold and wet)
Question are the pipes hoter or colder than the surrounding air?
You say the pipes/joints aren't leaking but bear in mind the water pressure increases at night when all you CA's stop taking showers and filling your pools.
Its not ant pee is it? Does it smell?
The hot water pipes should dry any moisture intouch or imediatley around?
A wild guess - is the insulations open cell foam possably with a non porus outer skin (Like a sponge in a plastic bag) - when the pipes are hot moisture on the pipes evaporates into the insulation, when the pipes cool moisture is sucked out of the insulation and condensess on the pipes.
You could always introduce air flow - dont no what it will do to your thermal properties though.
Good luck
Cameron
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Cameron


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