What about pools?

Q: What about pools? I have a friend building a pool. While I don’t want pool businesses to go out of business, I also don’t think she should be filling a new pool with water this year. – C.E., Sacramento

A: If properly maintained and covered, pools are not as big a drain as you may think. If the pool is replacing a lawn, it may actually save water use.

The average backyard swimming pool holds 18,000 to 20,000 gallons. After it’s filled, the pool only needs water to replace water lost to evaporation (or too much horse play). Pools generally are not emptied unless repairs are needed or due to poor water quality (on average, every three years).

By comparison, a lawn that covers the same square footage as the average-sized pool (18 feet by 36 feet) uses more than 24,000 gallons a year in irrigation.

Lap pools are built shallow, usually about 39 to 42 inches deep, and hold much less water than standard pools. That can cut the water capacity down substantially. A 45-by-8-foot lap pool holds about 9,500 gallons.

Used pool water doesn’t have to go down the drain; it can be dechlorinated and used to irrigate landscaping.

The major issue with pool water: Evaporation. In summer, a pool can lose an inch a week if left uncovered. But pool covers can cut down on evaporation 40 percent to 90 percent, depending on the model. In addition, systems can be used to capture rainwater (when it does rain) to replace pool water lost to evaporation.

This story was originally published February 10, 2014 at 12:00 AM with the headline "What about pools? ."