Every pool loses some water to evaporation, so a lower level doesn't always mean a leak. Before you worry, run a simple check.
Put a bucket of pool water on a pool step so that it sits in the pool, and mark the water level inside the bucket and outside it on the bucket's side. Leave it for a day.
If both levels drop by about the same amount, you're probably seeing evaporation. If the pool drops noticeably more than the bucket, water is going somewhere else.
Next, look for clues. Wet ground around the pool or along the pipe runs can point to the plumbing. Tears or loose spots in the liner point to the liner.
If the test suggests a leak, it's best not to wait. Lost water can soften the ground around the pool, and a small repair can become a larger one. We repair liners and plumbing, so call us and tell us what you found.