notarealemail - Yeah I know. Seems like a sense of humor is not SOP any more here. I got the joke too and I am uber-dense! :-)

I picked up one of these things at the thrift store for next to nothing http://tinyurl.com/jkc2h2r normally about $300 USD, I don't want it for a pool. I just want to heat up an animal water trough during winter months. Apparently I am too dense to understand how to do it without pumps. You can't. Definitely need some sort of water pump to pull the solar heated water out of the system when ready and then recycle it. I guess I'll need a couple of inline sump pumps (or gravity and 1 pump) and a Arduino*?

Found a great electronics outlet selling Arduinos dirt cheap ($4-10 usd each). Electronic Goldmine, PO Box 5408, Scottsdale, AZ 85261. www.goldmine-elec-products.com

*tongue-in-cheek humor?