On Thu, Apr 7, 2011 at 1:05 PM, Denny Esterline wrot= e: > Ok, looks like you've gotten more than a few good suggestions about > flow meters, hard to argue with the $10 option. :-) > > But as far as gray water heat exchangers goes.... there's plenty of > people before you: > > http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=3D1= 3040 > > -Denny Had I thought I invented something new, I wouldn't have shared it with all of you folks! Certainly there's nothing new about a water-water heat exchanger. I just want to put a figure on how much energy I'm reclaiming at present. My heat exchanger is a single-walled design, which although it is perfectly safe, is probably not "legal." The potable water is of significantly higher pressure than the gray-water, thus there can never be any accidental contamination. It's also an order of magnitude less expensive than the double-wall designs that use a 4" diameter copper pipe for the drain water. There's more to the system, and I hope to put up a web page to show some pretty graphs and things. --=20 Martin K. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .