There's a recent discussion on all of this, might wanna use the advanced search.
Filter mfrs say it's most efficient when pulling, based on the pump's tendency to emulsify any water in the mix if it's 1st in line. Others claim the centrifugal pump (JK) doesn't emulsify and you'll burn the pump up pulling it thru the FWS.
My kit pulls thru the FWS for 'bout 30k gallons now....... and Jeffery Epstein didn't kill himself.
2007 LBZ 3500 LT3 DRW Crew Cab, Sulastics, Putnam XDR 15K, B&W 30K-Turnover GN+Companion, Ride-Rite Air...EFI'd by Rob
2008 LMM 3500WT DRW Crew Cab, 8 'Flat/GN, Workforce Alum Toolbox, Ride-Rite Air Use-ta Haves 2006-6.0 3500 WT DRW ExCab Flatbed, 2005-LLY 3500 LS DRW Crew Cab, 2002-LB7 3500 LS DRW Crew Cab I Live my life in such a way that when my feet hit the floor in the morning...Satan shudders & says "Oh shit, he's awake!"