modified 14" swimming pool filter.

[markstrimaran]

Yes, with it connected that way, the water will be in the flush mode, on the sand filter, sinking kaldness, k1, would be agitated better.

The whole purpose is to keep a closed loop. So that pumping 500gph, with a 15 foot head, can be done with an efficient small pump.

I have not glued anything yet.

The blue drum, is currently holding water, and is connected to the aquarium on a closed loop. Part of the water changing system.

 

[kendragon]

If operating in the flush mode (up flow) then the pump should be hooked up the the waste port on the multi-port valve.
Otherwise, just keep it in the filter mode and reverse the flow like you got hooked up.
Be careful, the multi-port have holes bigger than K1 which will get sucked into the pump.