Build A Solar Hot Tub
Do you dream of a hot tub in the garden, luxuriating under the stars after a hard day’s work – or perhaps a tub party with champagne and lots of good friends?
Buying a commercial hot tub will set you back at least $3,000 and probably a lot more. Then you have to face the heating bills. But you can build a solar hot tub for less than $400, and the heating bills are zero. Zilch. Free.
Making a diy solar hot tub is very straightforward. The result will be the centerpiece of your backyard and will work in all climates – solar hot tubs work unbelievably well. You will need to fit a safety pressure valve to prevent steam build-up – the water will really get that hot!
Start with a good set of plans. These should include clear step-by-step instructions, a materials list, schematics and diagrams to show you exactly how to build a solar hot tub for yourself.
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The basic components of a solar powered hot tub and solar hot tub heater are:
- Solar collector panel
- Stock stand-alone tub
- Filter
- Pump (optional, depending on the site)
- CPVC pipes, connectors, elbows, etc.
- Safety, inlet and outlet valves
A simple solar collector can be made from a sheet of corrugated tin laid in an open wooden box. The box can be made of ¼ inch or ½ inch ply sheet edged with 2 x 6 inch lumber (or whatever you happen to have in your shed), and should be lined with a 1 inch sheet of insulating foam.
The water is heated in a series of ¾ inch CPVC pipes, laid and glued along each groove of the corrugated sheet in a serpentine pattern, so that cold water enters at the lowest point and exits at the highest. CPVC pipe is best, incidentally, because it has better heat tolerance then PVC.
The whole inside of the box and the pipes are painted flat black, and a sheet of ¼ inch (or thereabouts) polycarbonate glazing is attached to the top of the box to close it.
The tub can be any suitable stand-alone stock tank, from 150 gallons capacity (for 1 or 2 people) to 500 gallons or more.
If the collector can be mounted one or two feet below the solar power hot tub (perhaps by having the tub on a slight mound), it is possible to circulate the water through the heating system by thermosyphon action (ie no 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. You should fit a filter near the cold water outlet, otherwise you will need to empty and refill the tub regularly, which is a chore. Inlet and outlet valves (to control water flow) and a pressure relief (safety) valve should also be fitted.
Once you have tested the solar hot tub for leaks insulate as much as possible – external pipes, sides of the tub and the tub cover (very important, to prevent heat loss at night).
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. A diy hot tub does not have to be ugly!
The positioning of the solar collector is important. 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 promote the upwards flow of water through the collector pipes.
How long will it take for the water to heat up in your tub? 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. After that your main problem will be keeping the temperature down. Solar energy heating is very efficient!
Remember, proper planning is essential before you start to build a 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 advice and guidance from an expert in solar powered hot tubs.
There are many helpful people around to do this for you, but we have found an excellent source of plans, instructions and materials lists at very reasonable cost that we highly recommend. The kit comes with a full, no nonsense guarantee – you will get your money back in full if you are not satisfied for any reason with the product. We think this is a good, risk-free investment.
Solar hot tub diy can be great fun, and the results can be very rewarding. Start saving today by planning your own solar spa heater – you could have it in position by next weekend!
Click here to build a solar hot tub the green way
