"Brian Sharrock" wrote in message
...

You can make your own using two
large bore copper pipes. One inside the
other.

...................that bit I understand ...

The mains water is in the gap between the two.

....................................I can even grasp this idea ....

Using two reducing
elbows

Sorry should have been tee.

...... I'm afraid that I get lost about here ....
Can you provide a pointer to a sketch ?

Start again.. Lets have 15mm and 22mm pipe for understanding.

Parts:
- 1 three metre lengty of 22mm pipe
- 1 three metre lengty of 15 mm pipe
- 2 solder ring capilary 22mm x 22mm x 15mm tess. (that is a 22mm in the
centre of the tee)

- File out the the 15mm stops of each tee to make then slip 15mm pipe. Easy
enough, just elbow grease. Or drill it out if you have the right sized
drill.
- Cut the 22mm pipe to 2.5 metres in length
- Insert the tee on the 22mm pipe at one on each end.
- Run the 15mm pipe though one tee anmd push it until it reaches the other
end and run it through the slip of the other tee.
- Have the tees 180 dregrees to each other
- Solder up.
- Cover with insulation.

You then have cold water running through the 22mm tee and out the other tee
warmed up. The hot waste runs down the 15mm. This is now an effective heat
exhanger. The longer the better. I have done these over 20 foot in length
ona solar water heater and it was very effective and very cheap.

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