Ah okay, mine drains straight down into a drain in the floor (via gravity).

I thought about how 3d printing could help, but not everyone has access to such goods yet so I didn't mention it.

Hope it works!

I'm betting that it's getting sitting on the drain... Looks like it has a little valley in it that should let water through from the sides, but I bet it's covering up the hole now.

If it were mine, I'd probably find something flat and plastic to prop it up a bit on either side to let the water under it better.

It's just going out into the drain, I wouldn't think it would need to be filtered at that point.

What's with the piece of cloth/material on the bottom? That's probably getting wet and causing the suction effect you're thinking about about. Can it be removed?