Does water evaporate in a day?

How Much Water Does a Pool Really Lose in a Day?

One common question pool owners ask is whether water evaporates in just a day. The short answer is yes—but not all of it vanishes overnight. On average, a swimming pool loses about a quarter of an inch of water each day due to evaporation. That might not sound like much, but over a week or month, it adds up, especially in warmer climates or during peak summer months.

However, this number isn’t set in stone. Several factors can speed up or slow down evaporation. Sunlight is a major driver—longer exposure to direct sun increases the rate at which water turns to vapor. Wind also plays a significant role; a steady breeze carries moisture away from the pool surface, pulling more water into the air. Meanwhile, low humidity makes the air thirstier, absorbing water more readily than humid conditions.

So while a quarter-inch per day is a reliable benchmark, your actual loss could be less on cool, cloudy, still days—or more if it’s hot, windy, and dry. If you notice your pool losing water faster than that, it’s worth checking for leaks, especially around pumps, filters, and the liner.

Still, some water loss is normal. Instead of worrying about daily evaporation, focus on seasonal trends and maintain proper water levels to keep your pool running efficiently. A pool cover can also make a big difference, reducing evaporation by up to 90% when in use.

In the end, a little water loss is just part of owning a pool. Understanding the natural rhythm of evaporation helps you manage expectations—and keep your backyard oasis in top shape all year long.