| Do you dream of a hot tub in the garden, | | | | to 500 gallons or more. |
| luxuriating under the stars after a hard day’s | | | | If you can mount the solar collector at least one |
| work – maybe with a few good friends and a | | | | foot below the tub to allow thermosyphoning, you |
| bottle or two of good wine? | | | | should be able to avoid fitting a pump. Otherwise |
| A conventional hot tub will cost you at least | | | | a suitable pump of about 120 to 150 GPH rating |
| $3,000 to buy, and there will be the fitting costs | | | | will need to be fitted in the outlet pipe run. |
| on top of that. After that there will be the | | | | Short pipe runs with no sharp bends are best. |
| constant heating costs. But a solar hot tub can be | | | | Fitting an inline filter near the tub water outlet will |
| made for about $400, and the heating bills will be | | | | avoid the task of having to clean out the tub |
| zero. Zilch! | | | | from time to time. Finally you should fit inlet and |
| It is very easy to build a solar hot tub. You will | | | | outlet flow control valves as well as a safety |
| get a great addition to your backyard and you will | | | | valve to relieve excess pressure in the system. |
| be able to enjoy it in all weathers. These | | | | Test the hot tub system for leaks, then fit |
| systems get so hot that you will need a safety | | | | insulation everywhere – all outside plumbing, |
| valve to prevent steam building up! | | | | the sides of the tub and the tub cover (vital to |
| Begin with a good set of diy plans. Included | | | | minimize nighttime heat losses). |
| should be a full list of materials needed, clear | | | | Any structure you decide to build around the tub |
| step-by-step instructions and diagrams, plumbing | | | | will be for aesthetic or practical reasons such as |
| schematics and setting-up details. | | | | access, since the tub is designed to hold its |
| These are the main parts of a solar hot tub: | | | | contents without external support. |
| - Solar collector panel | | | | Proper positioning of the solar collector is very |
| - Stock tub | | | | important. In the northern hemisphere it should |
| - Filter | | | | face due south, or no more than plus or minus 10 |
| - Pump (option, site-dependent) | | | | degrees from it, and it should slope between 15 |
| - CPVC pipes, connectors, elbows, etc. | | | | and 30 degrees from horizontal. Also you should |
| - Safety, inlet and outlet valves | | | | slightly tilt the solar collector lengthwise to |
| A sheet of corrugated tin laid in a shallow wooden | | | | promote the upwards flow of water through the |
| box is the basis of the solar collector. Make the | | | | collector pipes. |
| box bottom from a sheet of ½ inch plywood, | | | | What time can you expect to take for heating |
| with edges made from 6 x 2 planks or similar, | | | | the solar hot tub water? Depending on where |
| and then line it with insulating foam sheet. | | | | you live it could take as much as two days to |
| CPVC pipes (3/4 inch will do) are laid and fastened | | | | reach a comfortable 110 degrees the first time. |
| along the corrugations and connected in series | | | | Then you will need to keep the water |
| allowing cold water to enter the solar collector at | | | | temperature down rather than up! |
| the bottom and exit at the top. Do not use PVC | | | | It is essential, however, that you plan in thorough |
| for the pipes, it has a lower heat threshold than | | | | detail before starting to build your solar hot tub. |
| CPVC. Use flat black paint for the pipes and box | | | | Know what size of tub you want and where you |
| interior, and glaze the top with a ¼ inch | | | | want to site it. Then seek out some good |
| polycarbonate sheet. | | | | professional advice – it really will be a good |
| The tub can be any suitable stand-alone stock | | | | investment. |
| tank, from 150 gallons capacity (for 1 or 2 people) | | | | |