Normally the flap will be against the plastic cover with water flowing.
I'd take it apart and see what's going on.
20K Gallon 20X36 Vinyl Inground
Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat
I have never seen the flap all the way open ... it is a pretty stiff spring. Unless you have a very strong pump and high flow rate, I think what you are seeing is normal.
Jason, TFP Moderator
18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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