Evaporation is a natural process that converts surface liquid into vapor form. More than 80 percent of precipitation is created by the process of evaporation. Any liquid form, even in your backyard swimming pool, is subject to evaporation from higher temperatures, lower humidity and high winds.
While all pools are victim to evaporation, normal rates range from a half inch to no more than 2 inches per week. In other cases a drop in water level can occur from splashing swimmers, slow leaks in the filter and liner problems. Tears, rips or punctures in the liner can cause water loss.
To slow the rate of evaporation, install a solar cover on top of the pool surface. A solar cover creates a vapor barrier, locking in heat from the sun and reducing evaporation. Solar covers are manufactured with UV-stabilized polyethylene, polypropylene or vinyl. One cost-effective cover is the bubble solar cover, made of thick-grade plastic resembling bubble wrap. Another choice is a vinyl cover, which is more durable and has a longer margin of wear and tear. The material is heavier and comes in insulated and non-insulated forms.
Determine if the pool liner is leaking with the bucket test. Fill a 5-gallon bucket halfway with water and mark the water line with a pen or permanent market. On the edge of the pool, draw a line in pencil to mark the top of the pool's water level. Place the bucket next to the pool, wait 24 to 48 hours, then measure both evaporation levels. If the pool lost more water than the bucket, your liner has a leak and may need patching or replacement.