Hula Hoop Heaters
Hula hoops are the base for the solar heaters. Estimate how many you will need to cover approximately half the pool. You will also need 6-mm-thick black plastic film, black vinyl tape, water-proof plastic glue, a white marking pen and scissors. The plastic film is available at hardware and home stores. Your working area must be large enough to hold a hula hoop laying flat.
Seal the seam of the hula hoop with the tape. Lay the plastic film on the work area, and then put a hoop on top if it. Trace around the outside of the hoop with the marker pen. Remove the hoop, and cut around the mark so that you have a circle of plastic film. Glue the edge of the plastic film to the edge of the hoop, and make four 3-inch slits in the plastic film near the edges of the hoop. After the glue dries, the hoop is ready to be used. Continue making heaters until you have enough.
How They Work
Although the sun is 93 million miles from the pool, its energy is still sufficient to heat the entire pool of water with a little help. The black surface of the plastic heats quickly from the sunlight and then transfers that heat to the air beneath it. The heat from the air is absorbed by the water. The hoop coverings also prevent the heat from transferring back to to the open air during the cooler night.
Safety and Storage
Never allow swimmers in the pool when the solar covers are also in the pool. They can easily block the view of someone who is hurt and laying on the bottom of the pool. The normal jostling and movement of the water can rip the plastic covering. When they're not in use, place the hoops away from the water to avoid temptation of using them as pool toys. Store the hoops during the off-season in a safe, out-of-the-way place, such as the rafters of the garage.