Attached spas and standalone hot tubs add plumbing, a heater, jets, and often a raised shell with a spillway, and every one of those is a place water can leave. A spa that loses water faster than the pool it shares equipment with is a classic detection case.

A specialist isolates the spa's plumbing and shell from the rest of the system to find whether the loss is the spa itself, a shared line, or a check valve letting water migrate between the two. Pinpointing it keeps the fix small.

A spa that drains toward the pool overnight, a spillway that keeps running when it should not, or a hot tub that needs topping off far more than a pool its size.

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.