Follow these simple steps to determine if you have an actual pool leak problem or if it's water loss due to normal evaporation:
1) Put a Bucket in the Pool and Fill it with Water
Place a 5-gallon bucket on the pool's steps. Add water to the bucket until it is the same height as the pool's water level. Mark both water levels (inside & out) on the bucket.
2) Let the Simple Bucket Test run for 24 hours
With the pool operating on it's normal schedule, let the bucket rest for 24 hours. If the pool has an automatic fill feature, make sure it is turned off.
3) Check the Results
Evaluate the water levels of the bucket and the pool. If the pool's water level is now lower than the level of the bucket's water, you likely have a leak.
Mike McFadden, Certified Master Home Inspector in Orlando, FL