Is there such a thing? I have a terrace on the third floor outside a flat which has a drain accessible via a small removable hatch. See photo. This drain keeps getting blocked with leaves etc and bits of dirt which causes the terrace under the decking to hold water like a swimming pool. How can I prevent this from happening? The property is rented by a bunch of fairly young girls and they can not be relied in to keep the drain hole clean and clear of any kind of debris. Is there such a thing as a unblockable drain cover or unblockable drain? Thanks for any advice.