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wrote:
Suppose we take a shower and collect 100 F greywater in the upper part of
a $30 100'x4" black plastic corrugated drainpipe coil containing 3 $20
100'x1" pieces of black plastic polyethylene pipe, with bidirectional
plug flow, like this, viewed in a fixed font like Courier:

shower
in
| ----------------------------------------- hot water to shower
| | Tl |
--------- sewer ---------
| | Tg | out | 120F |
| | | | |
| | | ^ | |
| | | | | |
| |1" |4" | | tank |
| | | | | water |
| | | | | heater |
| | | | | |
| | | | | |
| | | | | |
| | |---- | |
| | | | 55F |
--------- P ---------
| ---- Tc |
-----------------| - |------------------- cold water supply
----

This is so very very close to a GFX Star it isn't funny

What the Dr argues for is a el-cheapo electric water heater that is used
solely as a storage tank. The inlet to the pump is thru a check valve
that ties to the drain connection of the water heater/storage tank. Hot
out of the heat exchanger then goes to TWO places.

1. To a tempering valve to limit scald risk. the other input of the
tempering valve is the output of the normal hot water supply (electric,
NG, LP, or same inputs tank less)

2. Cold in on the water heater/storage tank.

Hot Out of the water heater/storage tank goes to Cold in on the normal
water heater.

Nick's figures and the Power-Pipe folks argue that the heat recovery is
equivalent to a 12-18KW electric heating element (for a 60 inch GFX).
In testing of the the GFX done at at least a couple of universities,
they found that the upper heating element in an electric water heater
NEVER TURNED ON in ANY of their testing.

The heat recovery of a GFX when used in this configuration jump 15-20
percentage points and becomes an almost level 65-75% Course we will
have 2KW/day losses in that storage tank. But with a CONSTANT input ot
the normal Hot water heater of 85-90 F, it will merely LOAF along to
deliver the HOT water needed.

One of the reasons for the higher heat recovery is that the flow rate
thru the coil LEAPS. The Taco pumps will move up to 20Gal/hr depending
on model to 20 feet. More realistically a Taco 006 or Taco 008 will
delvier upwards of 10Gal/hr at 10 feet of height. Now we have 2x-4x
MORE flow thru the coil than is flowing in the greywater. The graphs on
the GFX web site illustrate what happens with higher coild flow rates.

GFX Star controls the pump via one of two methods

a. Timer - showers at KNOWN times EVERY day

b. Differential temperature controller -sensors on coil and inlet to the
heat exchanger (GFX or Nick's) will trigger the pump when temp
difference exceeds a set point - i.e. 2 or 3 degrees