I've seen how badly steel and copper pipes sweat in hot and humid
weather, but I have not seem enough PEX to know how badly it sweats.
Does anyone know if PEX or CPVC (and other plastics) will sweat as much?
I'm guessing that it will sweat, but how much in comparison to metal
I'm asking this because I want to install some pipe inside my living
space, because they are regularly freezing in the crawl space, and
running heat tapes is costly on the electric bill, not to mention a pain
in the ass to check in cold weather.
I'm considering using PEX or CPVC for this job. Most of these pipes
will be going thru an interior wall, but a few feet will be exposed (and
covered with some sort of wooden trim). But I dont want water dripping
indoors that will cause damage.
Yes, I will cover the pipes with foam insulation, which I know helps a
lot with sweating, but is not 100% preventive.
I don't know where you are but my cabin has crawl space which is very
well insulated. I have one hot air vent from my NG furnace located there
installed. For more than 10 years, no problem. Plumbing
is all exposed PEX down there. In winter it gets down to even -30F
I would think there would be no difference since the sweating -
condensation - is caused by warmer and, consequently, "wetter" air
encountering a cooler surface. A water pipe, regardless of the material,
is going to be at whatever temperature the water in it is.
On Sunday, January 11, 2015 at 6:30:59 AM UTC-5, dadiOH wrote:
I don't think that's true. The temp of the surface depends on how
well the pipe material transfers heat. Copper is a great conductor
of heat. Plastic isn't. If you look at a temp cross section of the
pipe material, there is going to be a steeper gradient with the
plastic pipe than the metal.
I can't say I've compared them side by side, but I can recall lots of
metal pipes sweating, toilet tanks, faucets. But I don't recall seeing
a plastic pipe sweat. I would agree that it's still possible, probably
does occur under the right conditions, ie cold enough water, humid enough
air, but I bet it's a lot less than with metal.
As to the problem, I sure wouldn't rely on cpvc not busting when it
freezes. Pex would be better. Maybe I'm missing something, but it
sounds like only a short run is really exposed to cold, so I don't see
why it would be costing much to heat. It can also be on a thermostat,
so it doesn't heat 24/7. And they have variable type tape too, where the
resistance increases as it heats up, thereby regulating the temp/power.
I'd guess metal to sweat more. With plastic,
the heat of vaporization (vapor condensing
to liquid) will warm the pipe, and the plastic
won't conduct more cold (absence of heat) to
the surface of the pipe.
Christopher A. Young
learn more about Jesus
Pour a cold drink into a plastic, metal, and glass cup. The metal and glass
cups will sweat quickly because they conduct heat well. The plastic cup
will take longer but will eventually sweat too.
I have exposed PVC pipes in my pumphouse and they do sweat in the summer
time when cold water is flowing through them.
Cold pipe and hot humid air will sweat regardless of the pipe you use.
If possible, route the pipe so it is above the insulation on the warm side
(from heating the house). Even if you have to build a soffit of some sort
to lower the insulation below the pipes and keep them in the heated space
of the house.
If the pipes must remain exposed, I would cover the pipes with foam
insulation, making sure to seal up all joints. Then I would wrap that with
fiberglass insulation, and finally a layer of plastic tape or other vapor
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