To find a leak in a swimming pool liner, turn the pump and skimmer off. Examine the sides and floor of the pool for weak spots, which often occur when a leak is present. Another option is to place diluted red food coloring in a squirt bottle and squirt small amounts of the dyed water in the swimming pool. Watch the dye, as it typically flows out through the leak.
Alternatively, allow the pool to leak until the water levels stop dropping. Examine the pool liner above the water line to find the leak. In addition to examining the pool liner, inspect the equipment outside the pool for signs of moisture, and pressure test the pipes to determine whether a leak is present outside the pool.
To locate a leak in a plaster or fiberglass pool, look for visible cracks in the shell. Plug the plumbing lines, such as the skimmer and main drains, with rubber plugs. If the leak stops after you plug the plumbing, the leak is located in one of the plumbing lines. If the leak continues, it is most likely located in the shell.
Water losses of 1/4 inch or less are typically attributed to evaporation during the summer months. Splashing and backwash can cause the water levels to drop by up to 1 inch.