what size pump are you using?....what size pipe did you use to plumb the inside of the filter? and just a "tee" pipe connector in the plumbing does not make a true venturi, but eliminates the need for a check valve
pic 1...is the way i plumbed my 55 gal drums the street tee should be installed with the curve rolling down. i used 1&1/2" pipe for the inside plumbing. hose connected to input of "tee". this will easily handle 2200 gph.
pic 2...is the stock tank also 1&1/2" piping...this foto was taken with pump running. 1200 gph running thru the "tee" and not any need for an upper pipe...performs as well with 2200 gph going thru...
pic 3... showing why its 1&1/2" piping into the "tee" not just out...i plumbed thru the side wall of stocktank.