High water bills and increased chemical consumption are clues that a swimming pool or spa is leaking.

A simple test will confirm a leak in a pool or spa.

1. Turn off the filter/pump system and let the water settle down.
2. In situations where a dog may drink out of the bucket, or for general safety reasons, securely attach a stout "chicken wire" screen cover over the top of the bucket. 
3. A bucket or plastic wastebasket with no leaks of its own filled with water approximately 3/4 full and placed on the first or second step in the swimming pool
4. Anchor the bucket by placing a small brick or rock inside of it.
5. When the water in the bucket and pool settle, mark the level of the bucket's water inside the bucket. (To make a mark, simply make a scratch mark or use a piece of vinyl tape).
6. Mark the pool water level on the outside of the bucket.
7. Turn off the automatic filler if so equipped. (If a major leak is suspected, turn off pump and/or shorten the test to 12 hours).
   

After 24 hours compare the levels. Even if it rains, the water inside the bucket should be the same distance from its mark as the pool water is from the mark on the outside of the bucket. If the water level on the outside of the bucket is farther down from its mark than the inside level, the pool is leaking.

If the level inside the bucket is farther from its mark than the outside, the dog may be drinking from the bucket and the test should be conducted again.

Evaporation can consume a surprising amount of water. Measurements made in summertime in Southern Arizona have recorded evaporation rates of 5/8" a day or more. In a pool with 450 square feet of surface area or 15' x 30' up to 175 gallons or more will be lost. Not all pools evaporate the same rate even in the same neighborhood. Landscaping, exposure and backyard microclimates all govern evaporation rates. Heated pools also can lose more to evaporation than unheated pools especially when the air is dry.