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Our unit is the top floor unit of a 4-story building. There are several skylights and exhaust pipes on the flat roof.

The leak initially appeared right next to the skylight inside our apartment. Our roofer had come and did several things over the last year: putting down new rubber around the skylight, extending that new rubber all the way to the edge of roof; sealing around all the pipes, etc. Nothing worked at the end, so we finally replaced the skylight - as it seemed to be the culprit at that point.

However, the leak came back after the skylight replacement.

At this point, we also suspect the flashing because:
- it didn't leak during the winter, between all those snow storms and the melting of snow
- it also didn't leak during this wet spring/summer, except once, when it was raining like crazy.

So - based on the above, it would appear that the leak is not on the flat roof itself. Is that a fair assessment?

Use a hose (or at least a garden sprayer) and locate the leak. Really use a hose --start low and move upward very slowly -- over lots of time. ( It is always a 2 person job - one in -- one out. )

i'm not sure what floor you are on, but check around chimenys, skylights, exhaust pipes and any windows. you should give us details on the building configuration.

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Most times it is the flashing.

That's my top suspicion too.

How can we prove that, and also exactly where the leaky spot, is? If it's on the flat roof, we can just pour water over the spot. However, since this would be on the corner, or side of the wall, "pouring" would be challenging, I'd think?

Has a roofer checked out the flashing?

To make a long story short - we have a roof leak that we haven't been able to pinpoint. It doesn't appear to be on the flat roof itself: as it doesn't leak every time it rains, or during the winter season when we had tons of snow and the melting afterwards. In fact, since November last year, it only leaked TWICE only.

It only leaks when the weather is really crazy: (strong & crazy wind + heavy rain).

Our management company recommends doing a "water test" to find the actual location. Has anyone had experience with a "water test"? Never heard of it before, so not sure how effective (cost, time, accuracy-wise) it is.

Any other suggestions on how to pinpoint the origin of this leak?

TIA.