Building a Solar Hot Tub Is Easy
Dreaming of a long soak in a hot tub in your garden under a starry sky – maybe with some friends to share it with?
Buying and installing a conventional hot tub will cost you upwards of 4,000 dollars. After that there will be the constant heating costs. But you can build a solar hot tub for under 400 dollars, with no heating costs at all. Nothing!
Making a solar powered hot tub is simple. You will get a great addition to your garden and you will be able to enjoy it in all weathers. The water will actually get so hot that you will need to fit a pressure relief valve for safety!
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 panel
- Stock tub
- Inline filter
- Pump (option, site-dependent)
- CPVC pipes, connectors, elbows, etc.
- Pressure relief and control valves
A simple solar collector starts with a sheet of corrugated tin laid in an open wooden box. A sheet of ½ inch plywood will do for the bottom of the box, edged with 2 x 6 inch lumber (or whatever you happen to have in your shed), and then line it with insulating foam sheet.
A series of ¾ inch CPVC pipes are fixed in each corrugation causing water to enter at the lowest point of the solar collector and leave from the highest. 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.
You can try out various stand-alone tubs at your local hardware store and choose a suitable size, usually between 150 and 500 gallons depending on the number of people to use it at one time.
If you can mount the solar collector at least one foot below the tub to allow thermosyphoning, you should be able to avoid fitting a pump. Otherwise a suitable pump of about 120 to 150 GPH rating will need to be fitted in the outlet pipe run.
Pipe runs should be as short as possible, and avoid sharp bends. Fitting an inline filter close to the tub water outlet will avoid the task of having to clean out the tub from time to time. Inlet and outlet valves (to control water flow) and a pressure relief (safety) valve should also be fitted.
Test the hot tub system for leaks, then fit insulation everywhere – any exposed pipes, the external walls of the tub, and the tub cover (essential to lower nighttime heat loss).
Any structure you decide to build around the tub will be for aesthetic or practical reasons such as access, since the tub is designed to hold its contents without external support.
The solar collector must be sited correctly. It should face south as nearly as possible in northern latitudes, and be inclined between 15 and 30 degrees from horizontal. It should also be slightly tilted along its length to enable better water flow.
Will heating the water in the solar hot tub take a long time? It depends on where you live, but it could take up to a couple of days to reach a comfortable temperature of about 110 degrees the first time. Once there, though, you will find your main problem will be cooling the water rather than heating it!
Remember, proper planning is essential before you start to build the solar hot tub. Decide on the size of tub and where to locate it. Then the best, and safest, bet is to get some good professional advice.
Tags: build your own hot tub, diy hot tub, homemade hot tub, solar hot tub, solar hot tub heater, solar powered hot tub, solar spa heater
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