Electronic leak detection vs flood testing
Both answer the question “is this roof watertight”. Only one of them answers “and if not, where”.
Flood testing
Plug the drains, fill the area with water, wait, and watch the space below. It is simple, it is well understood, and it has been in specifications for decades.
What it costs you: a great deal of standing water on a structure that may not be designed to carry it. Time, filling and draining. Impossible on any slope. And when it does leak, you know only that water got through somewhere in the flooded area, with the assembly now saturated, which makes finding the breach harder than before you started.
Electronic leak detection
An electrical potential across the membrane, and current going to the one place it can get through. The membrane stays dry, the structure carries nothing, and the output is a marked location rather than a yes-or-no.
It works on slopes, on finished roofs, and in many cases under overburden. It also finds breaches far too small to fail a flood test today but large enough to soak the insulation over a winter.
When flood testing is still right
We are not going to pretend it never is. If a specification mandates it, if the assembly is not suited to electronic testing, or if the area is small, contained and easily drained, a flood test is a reasonable tool.
Tell us the assembly and what the spec says. If flood testing is the right answer for your roof, we will tell you so, and we do not sell it.
Tell us about the building
Describe what you have and what you are seeing. If this is not the right test for it, we will tell you that instead of selling it to you.