Dear Jim: I would like to use a solar system to heat my swimming pool water so my family can use it several more months each year. What are the various solar systems available and are there any do-it-yourself kits? – Beth L.

Dear Beth: In most climates, you can get an extra two to three months’ use of the pool by installing a solar system to heat the water. During midsummer, when the pool water often gets uncomfortably warm, you can circulate the water through the solar collectors at night to cool the pool.

There are several basic designs of solar swimming pool and spa heating systems and many are sold as do-it-yourself kits. The manufacturers will advise you as to the amount of solar collector area needed based on your pool or spa size and your climate (temperature and amount of cloud cover).

One interesting design uses a heat exchanger located in your attic. The heat exchanger is somewhat similar to a car radiator with a fan. The heat from the hot attic air is absorbed by the pool water. This not only heats the pool, but it cools your attic for lower air-conditioning costs.

Another unique design uses a 4- to 8-foot- diameter solar collector. It looks similar to a large TV satellite dish. Its parabolic shape focuses the sun’s heat on a small center core through which the pool water flows. It is ideal for colder climates and can also be used as a household water heater.

Special hollow solar decking is available. This is particularly good for aboveground pools, but is also effective for in-ground ones. The pool water flows through the dark plastic decking and absorbs the heat. This also keeps the decking cooler so it is comfortable to walk and lie down on. Complete aboveground pool kits with built-in solar decking are available.

The most common type of solar system uses flat solar collectors that lie flat against the roof of your house or garage. These systems can also be mounted on racks or just laid on the ground near the pool. They attach to the existing pool filter system pump so most are easy to install yourself.

Some rigid plastic collectors are available, but today most of the solar collectors are made from flexible tubing or sheets. This allows it to fit irregular surfaces such as the ground, a trellis or roof. Although it looks like simple tubing, it is specially designed for efficiency. Some include hook-and-loop straps so they can be rolled up and stored over winter.

Do-it-yourself installation kits usually include the collectors, check valves, solar valves, and return line tee so they are easy to attach to the pool filter system. Automatic controllers are available to allow you to set any water temperature. When the sun is hot enough, the system automatically starts.

Write for (instantly download – www.dulley.com) Update Bulletin No. 797 – buyer’s guide of 11 solar pool heating kit manufacturers listing designs, materials, installations, sizes, features and a solar kit sizing worksheet for various climates. Include $3 and a business-size SASE, and send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244.