after diving 6ft and unscrewing screws I found out that there is... nothing under the plastic main drain - I guess previous owners must have cemented the drain years ago - pipe still exist.
Would it be worthwile opening it again and maybe with a snake and new flexible pipe reopening it?
The problem I am currently facing is that there's no circulation unless a pool hose or vacum cleaner is in the pool.
3 returns are 1 foot deep, 1 skimmer also 1 vaccum port in the shallow side
any ideas / suggestions?