All summer the pool has been fine but over the last two weeks, we are loosing about 3 or 4 inches in a 28 x 14 inground pool every few days. I know its not the liner as when the pump hasn't ran for a couple days no drop .I have checked the filter pump heater and all the l=hoses and seals are tight and dry. Does anyone know a way to try and pinpoint where the leak might be as the pipes go under the skimmer then under the pool to the pump filter heater. Also the pool is surrounded by concrete slabs and interlocking brick.

thanks any help would be great