For ponding test, cut out a card board according to the size of the outlet. place multiple layers if required, this will improve efficiency of the ponding test.

for each layer you place, use scotch tape (big brown type) to seal the edges.

it's preferable that you get in touch with your neighbour one floor below you, you can do so by leaving your contact number.

There are two possible outcome from ponding test:-

(a) you neighbour will see leak in their unit, this probably an indication that there are areas in your bathroom area that maybe porous or water proofing system is bad (in certain cases, non-existent); or

(b) if there are ponding in your bathroom, it may be an indication that there insufficient gradient and water cannot be evacuated promptly or the tiles are uneven causing water to pond in certain area of the bathroom.

You should leave it as long as possible and monitor the ponding effects over a period of time.

Also, when you remove the blockage, you should observe how fast/slow excess water is evacuated.

Hope the above helps.

I suggest a bit longer.

It's very cumbersome once you move in having to know that the water proofing is done poorly and you need to re-do it again later.

In my condo, I had a sunken bath, we had to flood it for days and up to a month to observe for leakages. True enough, watermarks start to appear in lower units.

They had to re-do the entire water-proofing system.

Concerto by BCB.