We had the roof of the porch flood a while back and I realized then that the leaf mulch had blocked it.  When I saw it was filling up again, I knew what to do.  That is not just remove the mulch.  It is also to be ready to film it properly.  Here is the start of the draining process along with the various belching noises the downspout makes, and the water covers the opening.  It takes for ages to drain, and I couldn’t be bothered to film the whole thing.