I thought I was loosing excessive amounts of water from my pool. I was filling it everyday to bring the water level back to normal. Before you call a leak detection company in to see if your pool  has a leak there is a simple test you can do. If found this online at http://www.americanleakdetection.com:

1. Bring pool water to normal level.
2. Fill 5 gallon bucket with pool water about 3-4 inches from top.
3. Place bucket on first or second step of pool.
4. Mark water level on inside of bucket.
5. Shut off pump and mark pool level on outside of bucket.
6. Resume normal pump operation. Make sure auto/manual fill valve is off during test.
7. After 24 hours, compare the two levels. If the pool water (outside mark) goes down more than the inside water level, there is probably a leak.

In case of rain, repeat the test.

They also had a short video at http://www.americanleakdetection.com/tips-bucket-test.php  Fortunately for me the Sun was sucking it away.