How I built a Solar Heater for our Hot Tub
Step 1: Location
First you will need to determine if you have a suitable location to place the solar collector. If you do not then this is not a good option for you. I watched a spot in that yard throughout the day to make sure i got at least 6 hours of sun. also this App can help align and angle the collector.
Step 2: Construction
I constructed a wooden box from 2x4s and lined the entire box with rubber. This will create the dark color needed to absorb more heat. Under the box is 2 inch thick foam insulation. Inside is 50 feet on 1/2 inch irrigation pipe. I put nails in key places to aid in wrapping the loops.
Step 3: Covering the Collector
I found a thick plexiglass piece and used it to determine how big i could make the box. After the box was ready I carefully drilled pilot holes and screwed the panel to the box. The rubber I lined the box with acts a a gasket so I didn't use silicone. Also The piping to and from the pump is insulated and covered in aluminum then wrapped in the same rubber. Only a small portion of the line is buried under a walk way.
Step 4: Pumping and Timing
Until I can aquire a thermostat I used this timer to let heat build up between pumping cycles.