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water in a pipe

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Posted by no spam on March 22, 2007, 7:50 pm
I have been thinking about making a poor man's solar water pre-heater by
using a 100 foot coil of black plastic pipe (3/4" or 1").

But my numbers don't seem to add up so I need a little help.  Using the old
pi*r^2*h I come up with 3/4" pipe holding about 2.5 gal and the 1" stuff 4

Doesn't seem worth the effort, much less the money, for no more hot water
than that.

Also will "polyethylene coil pipe" rated at 100 psi hold up under the heat
and UV?  At $1US per 100 feet I'd think I'd save that much in water heating
if it only lasted one year.

Posted by Neon John on March 22, 2007, 8:14 pm

Yes It'll hold up.  I can think of one instance where a neighbor's
water supply from a high spring involves that pipe laying on the
ground.  It's been there since the 70s.  The cabin that used to be in
our family has the same arrangement and the pipe was installed
sometime in the mid 60s.  Still working fine.

As the formula indicates, volume goes up as the square of the radius
so using the largest pipe you can find is the key.  Even better is a
second water tank with the plumbing arranged so that the system will
thermo-siphon.  I did that one with one of my past houses and it
worked great.

John De Armond
See my website for my current email address
Cleveland, Occupied TN
All great things are simple and many can be expressed in single words:
Freedom, Justice, Honor, Duty, Mercy, Hope.  -Churchill

Posted by no spam on March 23, 2007, 4:41 pm
I have two plans running around in my mind.  The first is the take 100-200
feet of 1" pipe and run it back and forth over the roof of the trailer.  The
second is to try to use my water heater tank as storage for a thormosiphon
system.  The bottom of the tank is about 4' above ground level so by placing
the coil on the ground in a covered box I might be able to get a siphon.

Posted by GeekBoy on March 22, 2007, 8:21 pm

Then use the coil pipe on the roof then switch to PVC hot water piping once
you get back into the house.

Posted by harry k on March 23, 2007, 2:37 am
Minor correction.  Switch to CPVC.  You don't use PVC in a hot water

Harry K

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