There's a better way... Blow out the water, get a small air compressor, buy a special fitting that goes for the air hose chuck to a male hose thread. Start by draining the water heater (via the drain plug) then re-plug it. Drain your FW tank then run the pump dry.
Pump air into the city water connection, while building air pressure in the water heater open the faucets one at a time. Don't worry about getting every last drop out (it won't matter). Pour a gallon of the antifreeze into the traps (gray water tanks) and another into the toilet (black tank).
I winterize my rig 3-4 times a year for various trips. Being a master plumber, I winterize 10-12 homes each year (several have forced hot water heating systems). I can't be bother with trying to pump non-toxic antifreeze into the water lines, let alone the expense. This method works best for me and I hate the taste of Propylene Glycol in the morning.