Hello Ben, (If you are around)
I'm thinking of stealing your design and hacking it!
I'm daydreaming of a horizontally mounted Shower Waste Water Heat Recovery heat exchanger.
(On the ceiling of the laundry room).
Since the waste water is at near zero PSI, and I want keep the heat inside,
and make it cheap.. How about using 2" or 3" PVC for the water-jacket?
I would attach a 2" PVC flex hose to my tub drain, connect it to the SWWHR
input and drop the waste output with another flex hose into the washing machine drain pipe.
The trick would be sealing the 1/2 copper cold water pipe (L type) in the center of the end caps.
Since the gray water has such low pressure, it might not be a big problem.
Perhaps the copper supply pipe need not be in the center.?.
Maybe it can be positioned near the bottom of the PVC, to insure it's completely covered by the flowing waste water..
The PVC tube would be about 4 or 5 feet long and not quite level,
so it will fill up with gray water, before pouring out the higher end.
Insulate it well and start using less oil to heat my shower water!
Edit:
Someone invented the PVC version. Saw it on Ebay.
Waste water Heat exchanger Water Heater Green Energy - eBay (item 170390818624 end time Apr-02-10 19:06:03 PDT)