How do I find a pool leak without calling a professional first?

Do the bucket test: fill a bucket with pool water, place it on the top step, mark the water level inside and outside, and wait 24 hours. If the pool water drops more than the bucket water, you have a leak; if they’re the same, it’s just evaporation. Most leaks are in the liner (at seams, lights, or skimmers) or plumbing (at the pump or filter). Patch small liner tears yourself with a kit, but for bigger issues or plumbing problems, call a pro.