Building a Solar Hot Tub Is Easy
Do you dream of a hot tub in your backyard, luxuriating under the stars after a hard day’s work – maybe with some friends to share it with?
Buying a hot tub will set you back at least ,000 and probably a lot more. Then come the heating bills. But you can build a solar hot tub for under 0, with no heating costs at all. Zilch!
Making a solar powered hot tub is simple. You will have a great centerpiece for your backyard, and it will work in any climate. These systems get so hot that you will need a safety valve to prevent steam building up!
Begin with a good set of diy plans. These should include clear step-by-step instructions, a materials list, schematics and diagrams to show you exactly how to build the solar hot tub.
Basic parts of a solar hot tub are:
- Solar collector box
- Stand-alone tub
- Filter
- Pump (option, site-dependent)
- Various CPVC plumbing parts
- Safety, inlet and outlet valves
The solar collector can be a simple sheet of corrugated tin in a shallow wood box. Make the box bottom from a sheet of ½ inch plywood, edged with 2 x 6 inch lumber (or whatever you happen to have in your shed), and line it with a 1 inch sheet of insulating foam.
A series of ¾ inch CPVC pipes are fixed in each corrugation allowing cold water to enter the solar collector at the bottom and exit at the top. Do not use PVC for the pipes, it has a lower heat threshold than CPVC. Paint the inside of the solar collector box and the pipes flat black, and close the top with a sheet of polycarbonate glazing.
Use a stand-alone tub of between 150 and 500 gallons, depending on how many will be in it.
Mounting the solar collector at least one foot lower than the tub will enable thermosyphoning of the water. If unable to do this you will have to install a suitable pump (150 GPH should do) close to the tub outlet.
Short pipe runs with no sharp bends are best. Fitting an inline filter near the tub water outlet will avoid the task of having to clean out the tub from time to time. Finally you should fit inlet and outlet flow control valves as well as a safety valve to relieve excess pressure in the system.
Test the hot tub system for leaks, then fit insulation everywhere – any exposed pipes, the external walls of the tub, and the tub cover (vital to lower nighttime heat loss).
Because the tub is designed to stand alone, any surrounding structure that you decide to add will be purely for convenient access and aesthetics, such as covering up the plumbing.
Proper positioning of the solar collector is very important. In the northern hemisphere it should face due south, or no more than plus or minus 10 degrees from it, and it should slope between 15 and 30 degrees from horizontal. It also needs to have a slight tilt lengthwise to permit better water flow.
What time can you expect to take for heating the solar hot tub water? It might take as long as two days to establish a comfortable 110 degrees first time around. Then you will need to keep the water temperature down rather than up!
Remember, proper planning is essential before you start to build the solar hot tub. Know what size of tub you want and where you want to site it. Then the best, and safest, bet is to get some good professional advice.
