I get calls every year with people who fear they have a leak in their pool as their water level is going down. In many cases it is simply evaporation.
Pool water that is heated evaporates rapidly especially if the outside air is much cooler than the water.
We recommend that you do the bucket test. Take a regular bucket and fill half full with water, mark the level of where the water level is on the inside of the bucket. Place bucket on the top step of your pool and mark again where the water is on the outside of the bucket. Leave for 24hrs. If the water on the inside lowers the same as on the outside after 24 hrs this is simple evaporation.
Now you can relax, have a cold drink and enjoy your pool!