In my Designer, don't know which one you have, it is located on the left side of the basement area behind the water control panel. You have to remove the inside basement "wall" to get to it.
I use a whole home filter than filters everything coming in from the water line so my screen doesn't ever collect anything. It is a pain to have to remove that inside panel to get to it.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof