We're in NW Washington and this is our procedure. It doesn't use very much RV antifreeze ("pink stuff"):
1: Drain the potable tank
2: Drain the water heater and set the valve(s) to bypass. Leave the pressure relief valve open.
3: Attach the adapter (tire valve o/d to garden hose male) to the city water fill port.
4: Attach the air compressor hose to the tire valve above, with compressor tank at full pressure and outlet regulator at about 30 psi. Open the compressor outlet valve.
5: Go listen whether any air is escaping from the water heater pressure relief valve. If it is, you got the bypass set wrong. In three seasons, I can never remember which way the valve handle on our rig should be.
6: Go around the MH opening faucets, including bathroom shower and the outside shower if you have one. After all the faucets are blowing air, operate the toilet flush a few times to clear its line.
7: When everything is blowing air, shut off the compressor, disconnect and remove the adapter. Replace the cap on the city water inlet. Put the compressor away.
8: Take a bottle of "pink stuff" and pour about a cupful into each sink and shower drain.
9: This is optional - close all the faucets. Some folk leave them open, but it gets a bit messy if you forget and hook up city water in the spring!
10: You're done - grab a beer and relax.
We don't have a built-in filter on our water system - we use the in-line blue cylindrical ones - but I would take the filter cartridge out and put the bowl back on. I'll be doing this tomorrow, so if I find anything wrong with the procedure, I'll post a correction. It's a year since I last did it, and memory isn't what it once was.
Frank and Eileen
No longer RVers or FR owners