Your going to get a dozen ways to winterize your rig.
I take the easy/lazy way.
Buy 8 gallon jugs of rv antifreeze.
Drain my water heater and fresh water tank, and drain my low point cold and hot lines, and close all the valves. Remove anode rod and use a pipe plug to seal hole.
A gallon of antifreeze goes in the black tank. 4-5 gallons go into the fresh water tank. I run my pump and open the faucets until antifreeze comes out of all of them, hot and cold, running a gallon or so into the gray tank. Outside shower also. Run till all faucets are running antifreeze into the lines and traps. Put a quart of antifreeze in the pottie along with a cup of pure mineral oil for the seal.
Shut down pump and put her away till March.
Come spring, drain, run fresh water thru everything till it's clear, sanitize fresh water tank, and go.
Steve & Cheryl + Zoey, and Ziggy, our furry kids.
2012 Forrest River Lexington 283ts
2013 Subaru Crosstrek toad