Well it's that time of the year again here in Southern California time to fill up the spa and break out the BBQs. This has become a yearly ritual as well as a scathing reminder that electricity is not free.
Anyhow, my wife has been wanting to move in a greener direction and has been rather matter a fact about it as well. We now compost our organic waste and recycle that into our garden. Her new kick was "How can we heat the spa without using the electronic heater?" She got up on the roof with 50 feet of black hose and ran it back and forth a few times, hooked it to a pump and came up with the proof of concept. Yay! (The original idea was sourced from my coworker Gary who has a similar setup for his pool.)
Today we decided to move from conceptual proof to full on production. This Instructable will walk you through the process that we went through and try to help you avoid some of the gotchas that we found along the way. Hope you enjoy reading this as much as we enjoyed building/documenting this project.