How do vinyl liner pools leak, and can the leak be found without draining?

Liners leak at seams, at the fittings cut into them for the skimmer, returns, lights and steps, at pinholes worn by an abrasive floor or a sharp object, and at the bead where the liner hangs from the track. Water escaping behind a liner washes out the base, so a wrinkle, a soft spot underfoot or a liner pulling away from the track can each be a sign of a leak.

Draining the pool is a mistake: an empty liner shrinks and can fail completely, and the evidence of the leak drains away with the water. Liner leaks are found with the pool full by testing each fitting and checking the liner itself.