Yes. Most pool leak detection is performed with the pool at its normal operating level. Draining the pool is not required and is not part of a standard leak detection visit.
In fact, the pool needs to be full enough to test properly. If the water level is too low, key leak areas like the skimmer, lights, fittings, and tile line may be above the waterline and cannot be tested or observed. The pool should be filled to a normal operating level before the appointment.
The underwater inspection is performed by a technician who dives the pool. Dye testing, visual inspection of the shell, skimmer, lights, fittings, and drains, and pressure testing of the plumbing are all conducted with water in the pool. Draining would remove the very conditions that make many leaks testable.
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