Welcome to Mirage Enterprises!
Winterizing an RV is a relatively easy process. Have a water heater by-pass kit installed on your water heater, a water-pump winterizing kit, and it's a good idea to have a city water inlet blow-out plug.
Empty and flush out holding tanks at a nearby dump station.
Drain fresh water tank and water heater (leave the drain plug out of the water heater until spring). The water heater will drain a little faster if a couple of hot water taps in the unit are open. DO NOT open the safety valve on the water heater to help drain it because it might not seat properly again.
By-pass the water heater (antifreeze is not needed) either by purchasing (if not already installed) a water heater by-pass kit, or by removing the two water lines on the back (inside the unit) of the water heater and joining them together with a temporary by-pass.
It's recommended to "blow" the water lines out with air pressure (don't exceed more than 40-50 psi.) with a blow-out plug. Use an air compressor or a neighborhood service station’s air compressor used for filling tires. It's recommended to have more than one person do this step. One to hold the air hose on the blow-out plug screwed onto the city water entry (the same place the water hose connects to at the campsite) and the other to open the faucets. Open the hot and the cold tap ONE AT A TIME until completely drained. The toilet must also be drained.
Run RV (non-toxic) antifreeze through the RV plumbing system. Use 2 gallons (3 gallons on larger units). It is best to disconnect the water line from the fresh water tank at the pump side and use a separate suction line, or a pump winterizing kit consisting of a brass three way valve and suction line which stays attached to the pump permanently. Stick the suction hose into the jug of antifreeze making sure it goes all the way to the bottom of the jug. WITH ALL TAPS TURNED COMPLETELY OFF and the water heater by-passed, turn on the water pump and open a water tap (hot or cold) (the farthest one from the pump) and wait until the antifreeze comes out in a steady flow. Turn off that tap then do the next tap and so on until every tap in the RV is drained. Once again, do not forget to flush out the toilet. If the unit has an outside shower, don't forget it as well. Use the leftover antifreeze to poor down each sink drain and tub or shower drain (about 1/2 a cup), to ensure that the p-traps don't freeze up. Turn the pump switch off and clean up any antifreeze over spray left in the sinks and tub or shower. Open all taps and toilet valve by sticking something in the hole. Take care not to drop anything in the tank.
Remove batteries for winter storage.