Can anyone confirm if the top right hole is suppose to be plugged? It looks like that hole goes right to the rotor impeller.
Here is a long shot: take the impeller out and check the metal jacket for a vertical hairline crack.
Impeller has no visual crack.
Try running the Rena with empty media baskets. If the flow improves you've got the baskets packed to tight. If the flow stays the same there is another problem.
There's another problem...
Took a basket and a half full of rocks out and still the same flow.
When I get home, I'm going to check the valve assembly(?). A member suggested to check that out. Sheesh, what could it be or is this all the power this xp3 has?