Your pool will naturally lose some water to evaporation, some to splash-out and some to back wash waste water. You may also gain water from rainfall.
Common potential leaking places in a spa-pool are: The blower pipe; return-pipe; suction pipe; light fittings; around the weir, spa-jets and around them.
How to test for evaporation/pool leak
Bring the pool water to normal level. Fill a 5L bucket with pool water to about one-third from the top.
Place the bucket on the first or second step of the pool. Ensure the bucket is immersed halfway in the pool
Mark the water level inside the bucket.
Shut off the pump and mark pool water level on the outside of the bucket.
Resume normal pool pump operation.
After 24 hours, compare the two water levels. If the pool water (outside mark) went down more than the bucket's water level, there is probably a leak. If 2 levels went down by the same amount only evaporation has occurred.