Not sure as I always take my filter out to winterize mine. I put it in a big zip lock bag and store inside. Mine has to stay open to use for summer use. I close it off and winterize mine. I could not get the system to prime without closing that one off. By the way, the 2012s you can winterize just the Outside kitchen(if you have one) by taking out the filter. Turning that cut off we are talking about. Priming the lines and running water to the outside kitchen both hot and cold, then turning the cut off valves underneath the rear 1/2 bath sink, and then opening that valve back, flushing out the rest of the pink stuff and re-installing the water filter. That way you can use the camper for some winter camping without having to worry about the outside kitchen lines freezing. Just can't use outside kitchen water.
If you are going to put camper up for season, take out water filter, open ALL low point drains and then close that valve and winterize. You could leave the valve open or closed as I don't think it matters.
Don't forget to drain and bypass the water heater.
By the way, if yours has the outside kitchen, it will take about 4 gallons of pink stuff to do the camper.
2012 Sandpiper 365SAQ weighing @ 15k, Onan, 2nd air, slide toppers, TST
2013 F350 6.7L Lariat 4x4 CC DRW,Viair 1007, Ride-Rites, Edge CTS, B&W
2001 Chevy 3500CC DRW 4x4, 8.1L, 4.10 gears w/ Detroit TrueTrac
2001 Ford Excursion Limited 4x4 7.3L,V/B Spring Mod, ProComps, Hellwig Swaybar, & other 'Necessities'