Robert Gammon wrote:

Nick uses a LONG, SLOW moving body of water to extract heat. So in many
ways, it resembles a air conditioning condenser coil.

It also resembles a chair, if you wrap enough cotton gauze around both :-)

... His heat exchanger will need to be cleaned out periodically of gunk,
especially if toilets drain thru the same heat exchanger.

Not a good idea. It wouldn't make a good wheelchair either.

He argues that his will extract more heat than the GFX, and that may be true

Physics clearly tells me so. She seems to lie to you. How fickle.

... he will have a much larger unit (300 feet of 1 inch tubing is more than
6 feet in length when stacked as a single layer around a larger pipe that
holds the greywater)

You seem confused. In this condition, many people read more carefully.
Some even stop talking and listen :-)

The 1" pipe would be in 3 100' pieces inside a 100' x 4" black plastic
corrugated drainpipe which can be in 1) a 2' diameter x 6' tall coil or
2) a 7' OD x 2' ID x 4" tall flat spiral under a basement ceiling, which
uses less floorspace.

Nick