deartruc has the best response for you....if you get it off just go ahead and take the piece of junk out of your rig and install a straight pipe in its place!
Relieve all the pressure in your water system (no city water connected, water pump off, open faucet or two) and then using the supplied wrench, you have to apply pressure UP on the bottom to get the "knub" on the clear cylinder UP and clear of the "grooves" inside the white receiving head....its not easy or fun, guaranteed to splash water around, and most likely to rip the head right off the wall it is screwed to with those two stupid sheet metal/wood screws....don't ask me why I know this ;-)
Have patience it will come free but the likely hood of subsequent "automatic self removal" of this cylinder is VERY HIGH so if you choose to keep it installed, just be sure to keep a constant supply of towels around to commence drying up once it spins itself off the head and sprays water all over your nice RV!
I use the simple CAMCO inline (blue) water filters from on line, camp stores or Walmart..very cheap, easy to use, remains OUTSIDE my rig and I simply toss them in the garbage after about 6 months or so.
Ed & Chris
Josh & Jaclyn
2012 Suburban LTZ
2013 Rockwood Roo 233S