The shell is the pool itself: gunite and plaster, a fiberglass tub, or a vinyl liner. Hairline cracks, liner tears, and separated tile lines let water seep out slowly, and the settling soils around Sacramento and the foothills can open them up over time.

Detection specialists use dye testing and pressure checks to tell a cosmetic surface crack from one that actually leaks, so you are not paying to chase a mark that holds water just fine. Finding the real crack keeps the repair targeted.

A visible crack in plaster or a vinyl liner, a stain that reappears after patching, or a water line that settles at one particular spot and then stops dropping.

Confirm it is a real leak before you call anyone. Rule out evaporation with the free water-loss test or the bucket test. If it is more than evaporation, a detection pro pinpoints the exact spot so any repair stays small.