Paramount MDX R3 Bottom Drain

[RIRSZ]

The side port is supposed to do exactly what you said, but once it submerges the lid, you shouldn't have any more water coming through there. You can test this by covering the side port in the pool with your hand and seeing if water level above the lid drops.

 

[DOMO]

Hi. Yes, that's correct, when I cover that side port, the water drops a little and them fills back up when opened up.