View Single Post
Old 03-01-10, 11:49 AM   #1
Supreme EcoRenovator
AC_Hacker's Avatar
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,002
Thanks: 303
Thanked 712 Times in 532 Posts
Default DIY Grey Water Heat Recycling...

There is an interesting entry in Wikipedia on Water Heat Recycling.

This photo is shown:

The article states:

The retail price for a domestic drain water heat recovery unit ranges from around $500 to $1,000. For a regular household, water heating is the second highest source of energy demand. The savings in energy results in an average payback time for the initial investment of 2-10 years.
It seems to me that someone could duplicate such a device for much less than $500 to $1000, and the payback would be much shorter.

I also found that there is a company called GFX Technology that makes such a device. They have a PDF of performance curves located here.

There's even a Bob Villa video .

Here are other companies in the same business:

The important features I can see are:
* counter-flow - drain water goes in one direction, incoming cold water goes in the opposite direction (larger 'delta-T', makes the efficiency higher.)
* drain water flows in a thin film inside the heat exchanger - this assures maximum exposure of the hot drain water to the cold incoming water, making the efficiency higher. (question: is a special structure required for this to happen?)
*copper construction assures good heat transfer. (question: is the coil soldered to the drain water pipe?
* it also seems to me that encasing the whole assembly in insulating foam would improve the efficiency even more.

I have seen projects where plastic 55 gallon barrels and long pieces of PEX are coiled inside to make such a system, but this compact copper unit seems to be elegant, compact efficient and highly buildable.

Here are more photos of the GFX units:

With domestic water heating being the second biggest energy use for homeowners, this seems to be a natural target for our efforts.

Claims of efficiency seem to run as high as 50%, this would hold for fossil fuel use, and also for wood water heating, as well as for the size of a solar Domestic Hot Water (AKA: DHW) array required to supply DHW to a home or business.

Best of all, no moving parts.

Build It Solar has a relevant link here.

Here is a link to a Grey Water Heat Recovery Calculator.

Are the wheels turning?



Attached Images

Last edited by AC_Hacker; 03-01-10 at 11:51 AM..
AC_Hacker is offline   Reply With Quote