I'm in TX, so the last thing I want is something hot.
I have a "cool pool" made from a 6' diameter galvanized water trough. I rubberized the inside with a rubber paint so the chlorine doesn't attack it. I glued rigid foam to the underside and insulated the outside with the reflective bubble wrap insulation, it then got clad with t&g cedar with stainless banding to hold it in place. Very decorative for a redneck pool!
It has an Intek cartridge pool filter, a submersible light (actually a 12v boat transom light that screws into a boat drain hole) and a wood fired heater made from a 1 1/4" coil of stainless steel tubing (about 25' of tubing). You start a fire in the center of the tubing and the "thermal siphon" principle circulates the water, drawing cold water in the bottom and warm water out the top. It can heat the pool about 6 degrees/hour. The idea isn't to make it warm like a hot tub, but a temp of 86- 96 seems to suit me just right for relaxing. I use it well into late October- early November each year. It even has a patio umbrella that I can raise and lower as needed.
