From:
Subject: DIY solar heating
Date: 24 January 2005 18:06


You can make your own using two
large bore copper pipes. One inside
the other. The mains water is in the
gap between the two. Using two
reducing elbows and filing out the
pipe stops inside the the fittings so the
inner pipe can slip you can easily make
one yourself. Once filed out you
solder it up with a powerful blowtorch
and wrap with insulation.

Have you actually done this, at 20ft long?

Yep.

The reason I didnt suggest
this approach is differential thermal #
expansion. I cant imagine how a
soldered joint would survive in such a creation.

Thermal expansion is not that great.

Sounds like a real recipe for
leakage to me.

Nope. Works well.

- 1 three metre lengty of 22mm pipe
- 1 three metre lengty of 15 mm pipe

why do you recommend 3m?

An e.g, and they come in 3 metre lengths.

And more to the point, why 20ft? Theyre
usually 2-3ft.

An e.g., from an different application.

- Solder up.

why do you recommend solder,
which is soft and cracks easily, when the
2 tubes have differential thermal expension?

It worked well. You could use compression joints tightly screwed up.

- Cover with insulation.

why do you recommend insulation?

Are you serious?

I'm not clear why cold to lukewarm
flow, which is what goes round the
outside, would need insulation.

You are serious.

You size up the copper pipe to suit
either a shower or a full 110mm
waste.

Where do you get the 110mm copper
fittings?

Nearest equiv and from industrial merchants.

And how do you drill 110mm
holes in them?

You don't drill, you use fittings as described above.