This past year I reconfigured my RO to increase brix output. I now have a 3-post 4x40 RO with a 10gpm HP pump running recirc. The pump output typically runs at about 225-250psi. I'm getting about 1.5gpm permeate flow with my concentrate draw set at 0.75gpm to keep up with the evap rate of my arch. Recirc flow exceeds the 5gpm flowmeter, but math says if would be 7.75 gpm. With a 1.75 brix sap inlet I'm only getting 4.5-4.75 brix out. With running recirc I expected the concentrate output brix to be quite a bit higher.

Any suggestions on what I may need to change to get higher brix out or are my expectations too high?