"Robert Gammon" wrote in message
. com...
Power-Pipe now has a US web site that gets them around the customs issue.

The pump with differential temperature control is the secret to higher
recovery rates. Flow rate thru the coil in excess of flow rate of
greywater will more efficiently transfer heat to the potable water.

Actually you could take this a step further and use a water storage tank
intended for solar applications. It has an internal heat exchanger, and
you could route a working fluid thru Nick's, a GFX, or a Power-Pipe that
was NOT water for higher heat capacity.


What working fluid would that be? Water has a much higher heat capacity
than most any other fluid you're likely to find/afford. Best to stick with
simple water.

As regards to increasing fresh-water flow, the GFX folks recommend plumbing
so that the cold water enters the heat-exchanger *before* splitting to go to
the hot-water heater and the cold tap in the shower. So the 'cold' water
side of the shower is pre-heated (need less 'hot' water to stay comfortable)
as well as the inlet to the hot-water heater. This raises the flow on the
fresh-water side to equal the greywater flow.

Putting a pump to circulate between the 'dip tube' into the heater, and the
drain could improve the circulation through the fresh-water side of the gfx.
But you best be sure to insulate the piping. But with this setup would you
still want the heat-exchanger's fresh-water outlet going to the cold shower
tap?

I'm a bit skeptical. After all, the greywater coming in is cooler than the
hot-water heater until you've cooled the bottom of the tank. But the bottom
of the tank is receiving fresh-water out of the hx. Increasing the flow
through the hx with a pump is going to put warm water into the hx inlet,
mixing with the cold water from the main. Then sending the mixture of cold
inlet water, and warm water from the heater drain into the hx. Just so you
can put warmer water back into the bottom of the heater via the 'dip tube'.
Net results seem to be higher flow, but the average temperature of the
fresh-water side of the hx is higher and the greywater outlet temperature
will be higher. I would wonder if the increase in heat transfer due to
higher flow on one side only can make up for the lower temperature
difference across the heat-exchanger walls.

daestrom