Owning a pool is an expense in itself, and heating it is even more of an expense. The climate in which you live will determine how well a pool can be heated and the cost to maintain some warmth in that outdoor oasis. Using a water heater is not the best idea to add warmth to your pool, though. Just because it may work does not mean it is the right way to do things. Water heaters are sized based on a few factors, and these factors will help you realize that using a home water heater to heat your pool is not a good idea.
Why Won’t a Home Water Heater Work?
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Pool pumps can move an extreme amount of water rated in gallons per minute (gpm). Water heaters can only handle maybe one quarter of the capacity necessary to efficiently add some warmth to your pool. Tankless gas water heaters have the highest recovery rating of about 8 gpm, and pool pumps can move anywhere from 30 to 73 gpm. Tank-type water heaters have much lower recovery rates that vary and are based on gallons per hour and not gallons per minute. Even large-tank gas water heaters (75 and 98 gallons) average around 135 and 150 first-hour ratings. When you put that into the perspective of a 24,000-gallon pool, it is not a lot of warmth added in one hour.
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A pump moving a limited amount of water through an 8 gpm or 200,000 Btu/hour tankless gas water heater will take roughly one hour of running to warm up the 24,000-gallon pool 1 degree (24,000 gallons x 8.35 pounds per gallon = 200,400 pounds of water or roughly 1 Btu per pound). So to raise a 60-degree pool to a more comfortable temperature of 78 degrees, it will take 18 hours of running, not including any heat loss. A 50-gallon electric tank-type water heater will take six times that to heat the same volume of water. That will surely add a lot to the electric bill even if it could possibly overcome any heat loss at only 30,000 Btu.
In addition to the lack of efficiency involved in using a water heater to heat a pool, there is the subject of chlorine. Water heater manufacturers void product failure warranties if the equipment is used for corrosive materials. Chlorine is a corrosive material, and the water heater will not withstand the pool heating task for long. Even saltwater pools may have a certain corrosive properties that can be detrimental to a water heater.
Choosing a Proper Pool Heater
Pool heaters are specifically designed for just that: heating a pool. They should be seriously considered over a home water heater. There are a variety of pool heaters available. The climate where you live needs to be considered in determining the right pool heater to use.
Heat pump pool heaters are a great choice for Southern locations and warm climates. Solar pool heaters can be a good choice, but it depends on solar resources. Gas pool heaters are very versatile in any situation and climate. A pool heater can be expensive to operate if it's not sized appropriately. It is always best to have your pool heating needs assessed by a professional from your specific location. For the benefit of your wallet, look into different ideas other than a home water heater to warm your outdoor oasis.