We have had a few posts on the topic before..
Maybe you can find some info, looking here:
http://ecorenovator.org/forum/conser...er-heat-2.html
http://ecorenovator.org/forum/conser...recycling.html
I'm still interested in a DIY scheme, since my ground/city water runs pretty cold..
And, my plumbing needs some work downstairs anyways..