Evaporation is normal
Sun, heat, wind and low humidity all pull water out of a pool. In a Sacramento summer it can be a noticeable amount every week, so a dropping water line is not always a leak.
The bucket test
Fill a bucket with pool water and set it on the first step so the water inside is level with the pool. Mark both water levels, wait 24 hours with the pump running as usual, then compare.
If the pool dropped more than the bucket, you are likely losing water beyond evaporation and should have it checked. Repeat with the pump off to help narrow down where the loss is.
When to call
If the bucket test suggests a leak, we can confirm it and locate the source before the loss gets worse.