Swimming Pool Water Usage

By the Numbers

• If a standard size swimming pool is 18 by 36 feet with a depth of 4 feet, it will hold about 19,400 gallons. This is a one-time investment, however, as pools that are properly maintained will not have to drained and refilled even partially for many years. Evaporation and water loss through swimmers and splashing accounts for most of the water loss in a pool. A typical pool, with solar cover, of this size will lose about 50 gallons through evaporation in a single day; this will lower the water level only by about 1/8 of an inch. On average, the combined loss between evaporation and splashing water loss means that pools will use about 20 inches of water per year.

Comparisons

• To put the numbers in perspective, the City of Sacramento released a comparison between the water usage of pools and the water usage of other types of ground coverings that can take up the same space. The amount of space taken up by an 18 by 36 foot pool will use about half as much water as it will take to irrigate or water the same amount of lawn space taken up by a garden or grass. Like watering the lawn or garden, rainwater can also be used to replace pool water lost to evaporation; mesh covers are designed to collect rain water, which is chemically treated and just as safe as city or well water.

Considerations

• No 2 pools are identical, and there are some important considerations to look into when examining personal pool water usage. Old fixtures or a leaky pool can greatly increase the water that is lost. Keeping the pool covered when not in use will help prevent evaporation, and the warmer the water is kept, the faster it will evaporate. Structures such as fountains and slides that are continuously fed with water will also increase the rate of evaporation. Draining pools that are not properly maintained will greatly increase water usage, as will frequent backwashing to clean out old or dirty filters. Even the amount of time the pool is in use will effect water usage, as the more swimmers that are in the pool, the higher the rate of water loss is.

Other Uses for Pool Water

• Pools can also be used as a reservoir during times of drought. When needed, the water from the pool can be re-appropriated for use in tasks like watering the lawn to washing cars. Some local fire departments also rely on pool owners to lend a hand during periods of drought. Long, dry spells can result in not only overall increased water usage and a strain on an area's water supplies, but it can also mean a dry, brittle landscape that is susceptible to fires. Some fire departments will even sign agreements with pool owners that their water can be used to fight fires in case of emergency.