"Mark" wrote in message
...
IMM typed:

FFS how many showers do you people have a day.
Has anyone given the slightest thought to how efficient this will
be, and the likely rise in temperature achievable.
Even I cant be bothered to (use) one of these.

Another know-it-all. Do a Google on groups and type in gfx. If
you did that first you wouldn't nake such an idiot of yourself.
There are some Americans who have these installed and reported
figures on them. The average temp rise is 17C.

Must be distant Dimm relatives of yours,

Even the US government is on about it.

http://www.eere.energy.gov/femp/pdfs...ty_film_ex.pdf

The US government conclude:

"however, based on our measurements, a 30 to 50% savings in the energy
needed to heat shower water seems reasonable."

sigh
ive built two of these, BP1 was 25m ( note 25 meters !) of 8mm pipe coiled
inside a 150mm soil pipe with stop-ends fitted with 1-1/2 waste fittings
to
connect to shower 3ft away, cold water flow was set to 1gpm.
After running hot shower for 15 min to ensure everything had warmed up I
measured the input and output temperatures, the gain was a staggering
............... 1 deg C

Having realised I need a MUCH bigger heat exchanger came BP2.
This one would be completely impractical to actually use but..
A friend was ripping out a warm-air CH boiler, Ah that looks big enough.
So I built a tank to hold HE and arranged plumbing so the tank filled with
warm water before exiting, same flow rate and test as before.
The gain in temp was 4 deg C

Conclusion, don't bother unless you are chucking huge amounts of hot water
down the drain, fit solar panels instead.

You are obviously and idiot and did it wrong...and can't read either. The
US governments tested it and says: "The key to this patented device was the
inventor's observation that wastewater clings in a film-like fashion to the
inside wall of the pipe as it undergoes gravity flow in the open drain, and
this warm, falling film transfers heat through the pipe"

The pipe has top be "smooth" in the inside. Boy are you dumb!