# "sweaty" cold water supply pipe

snipped-for-privacy@ece.villanova.edu wrote:
<snip>

Do you -really- think that water coming in at 50 degrees (IINM that is about normal underground temp) at high velocity, at least that of an open fixture, is going to pick up much useable heat in 10 ft?
I suspect he is referring to non-flowing conditions. I kind of lost track here. Does he say that it is in a basement? In my case it is and the pipe is coated with condensate from the point it enters until it disappears into the ceiling joists. Temp in my basement is around 65, too cool to sit down there in a t-shirt.
Harry K
Harry K
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Sure, based on the OP's description and the fact that condensation can dramatically increase the air-to-pipe thermal conductance by a factor of 100 or more... 2 gpm is 960 Btu/h-F, so warming it 1 F takes 960 Btu/h, ie 1 pint of condensation per hour, about 3 drops per second. I can imagine that, in continuous use, altho most usage bursts are a lot shorter.
It might make sense to change this pipe to fin-tube vs insulating it :-)
Nick
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OK -- I am the OP, so let me clarify some points. 1. Yes, the condensation only appears on the first 6 feet or so of the 1" pipe. That pipe runs vertically near the basement wall where the city supply enters. The 1" pipe is pretty dry after it turns horizontal and continues to be dry as it branches off to the water heater and converts down and branches to 1/2" pipe runs for the house cold water supply.
About 1/3 up the initial vertical 1" pipe run, the 1" pipe bifurcates to supply the underground sprinkler system. This bifurcated pipe rises in parallel with the rest of house supply for about 3 ft and then exits the house. This run also "sweats" heavily.
My initial thought was that the 2 hour runs of the sprinkler may be primarily responsible for the sweating. However, I have not noticed significant variability in the condensation between days (and times) that the sprinkler runs vs. when it doesn't.
Also, the rest of house supply pipe continues to have heavy condensate for 2-3 feet above where the sprinkler branches.
Also, btw, we heat the hot water with gas and we live in New England.
Finally, last night I insulated the first 10 feet or so of the 1" runs (except around the valves and water meter), plus the branch to the sprinkler system.
We will see what happens (though today is significantly less humid so it may not give it a good test).
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wrote:

Whaddya expect, this is FEAR FACTOR.
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--
-john
wide-open at throttle dot info
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snipped-for-privacy@bellsouth.net writes:

How well sealed is "well sealed"? Is it enough to buy the Home Chepot middle-grade stuff that comes with taped edges that you push together?
My sense is that the adhesive tape is enough to keep it on the pipe but not enough to make a real seal. Is there stuff that is better to buy or should I cover the seam with something like duct tape?
Thanks
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In alt.home.repair on Fri, 22 Jul 2005 01:32:04 GMT blueman

If you put it on when the pipe is dry, almost anything will keep the humid air from touching the pipe after that. No humid air, no condensation. If part of the pipe is dry, wipe it off with a towel first.
Personally, I doubt mold or anything will grow on a little dampness on a copper pipe, but this should prevent any.
If youre still not sure, open part up after 6 months and check it out. But you have to look right away. The moment you open it up, humid air might start to condense on the pipe.
Meirman -- If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary.
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writes:

As long as it holds, yes.

If you have concerns wrap some tape every 12" or so. Duct tape or electrical tape will work. Mine has b een holding for about 20 years, but that does not mean what you buy today will.
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blueman wrote:

Well I heard this insulation was primarily for the cold water pipe, not the hot water pipe.
--
Respectfully,

CL Gilbert
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I have it on my cold water line, no problems

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Insulated properly there will be no condensation to trap.

No
Yes, but if you run a lot of water it will move along the line as it cools down. Depends on your particular use, temperatures, humidity, etc.
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if you leave the pipe uninsulated you will avoid the killer mold in the insulation problem, which is what you probably heard about on tv news last year. a spray-on aerosol can foam insulation would ease your mold worries if you insist on insulation. check with your local building inspector for requirements and ideas.
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