Drain water heat recovery?

[Skyco]

Anyone use a drain water heat recovery system?
I'm thinking of tinkering with a home made one.
Just seems silly to be dumping 100deg water down the shower drain when I'm simultaneously pulling cold water out of the well to heat it...
I figure if I can preheat the incoming water with the drain water I can save a little on the electric bill.

 

[beenthere]

A large holding tank for the gray water with a coil in the center for the incoming cold water might take the chill off. Depends on the space you have and the treatment you might need to keep odor and bacterial action to a minimum (guess that bacteria will create some heat too ). Might also pump off some of that gray water and feed the toilets, but suspect some pre-treatment and filtering would be needed.

I pre-warm the cold water before the house hot water heater using a 30 gal stainless tank that has a 3/4 copper coil that has wood boiler water circulating through it. During the winter heating season, that water is 110 - 170 deg F and it works quite well. Shown here to the right of the woodburner (water system).

 

[Kays Supply]

Check your state plumbing codes. In Illinois you must use a double walled coil to separate the gray water from the coil holding potable water. The cost of that would take a long time to offset gain. If you do decide to do that, use a sealed holding tank that catches shower , lav, laundry and lav water. Vent it to the plumbing vent. It will cool between uses and your gain will be minumized. Make it as small as possible and have a way to drain it into the sewer. Sounds like a lot of trouble for pennys of gain.