The rooftop patio drain was blocked on this home we recently inspected in Brampton, Ontario. If you’d like to add a pool it’s probably best to get one professionally installed.
In all seriousness, general maintenance should not be overlooked even if you are selling your home. Thankfully this flat roof was installed well and did not leak into the home. Otherwise the entire home and downstairs neighbors would have had extensive water damage all for 5 minutes of work to unplug the drain on the terrace.