Here is how I did it:
First I removed the water filter which was mounted in the bilge just past the valves for the water tanks. After the filter was removed I opened the water tank valves one at a time and let the water drain into the bilge.
After the water tanks were empty I placed this adapter that had a short piece of hose connected to one side and connected the other into the boat's water supply hose.
The other end with the small length of hose went into a gallon jug of antifreeze. Then I began to operate the water system and pumps operating the faucets one at a time. Starting with the sinks.
As each faucet was opened up I collected the antifreeze that came out in a clean container.
I then returned the antifreeze collected back to the antifreeze jug and continued winterizing the water system. You should do this procedure in the order of potability and sanitation. Here is the order I used:
3) Shower sump
4) Head (Note: after the collected antifreeze is put into the head there is no need to collect it. Just pump it into the empty holding tank and then drain the holding tank.
I then used a small wet/dry vac to suck up any remaining fresh water that is still in the fresh water storage tanks and also use it to suck the lines from the water tanks to the bilge area. Since no antifreeze was used in the tanks you save money now because you did not need any extra antifreeze and it also saves you time in the spring because the tanks do not need to be flushed out as much. Total amount of propylene gycol antifreeze used was one gallon. NOTE: You may need extra if you have other water systems like a washdown but, the amount should be minimal. Also if you are winterizing in severe colder climates where tempertures reach negative numbers for days at a time you will need to make sure that you are using an antifreeze that goes well below the expected tempertures you will experience.
NOTE: You may want to test the antifreeze after you've winterized the water system. To see how to do that click here.