Build A Solar Hot Tub
By Article Expert on Nov. 19, 2009.
Are you dreaming about a long soak in your own hot tub under the stars – maybe with a few good friends and a bottle or two of good wine?
Buying a hot tub will set you back at least 3,000 dollars and probably a lot more. 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. Free!
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. You will need full schematics, clear building diagrams, comprehensive lists of materials and professional advice.
The basic components of a solar hot tub are:
- Solar collector box
- Stock tub
- Filter
- Pump (optional, depending on the site)
- 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, with edges from 6 x 2 lumber or whatever comes to hand, and then line it with insulating foam sheet.
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 causing water to enter at the lowest point of the solar collector and leave from the highest. Use CPVC for the plumbing, rather than PVC, because of its better heat tolerance. 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 the solar collector can be mounted one or two feet below the tub (perhaps by having the tub on a slight mound), it is possible to circulate the water through the heating system by thermosyphon action. If this is not possible you will need a pump rated at about 150 GPH fitted at the outlet from the tub.
Try to arrange the shortest possible pipe runs and to avoid 90 degree 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. You will also need control valves at tub inlet and outlet, and a pressure relief valve for safety.
Test the hot tub system for leaks, then fit insulation everywhere – external pipes, sides of the tub and the tub cover (very important, to prevent heat loss at night).
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.
Proper positioning of the solar collector is very important. In northern latitudes place it facing due south, or within 10 degrees of it, and sloping at between 15 and 30 degrees from the horizontal. It should also be slightly tilted along its length to promote the upwards flow of water through the collector pipes.
What time can you expect to take for heating the solar hot tub water? Depending on where you live it could take as much as two days to reach a comfortable 110 degrees the first time. After that your main problem will be keeping the temperature down!
It is essential, however, that you plan in thorough detail before starting to build your solar hot tub. Decide on the size of tub and where to locate it. Then seek out some good professional advice – it really will be a good investment.
Category: Home Improvement