This is the time of the year where we get many calls on "How do I winterize my VacuFlush Sanitation System". We'll its easy. I am going to keep this simple.
1) Lift the foot pedal up and add water to the bowl and flush the toilet. Do this 3 or 4 times, This helps to clean the hoses and vacuum tank and vacuum pump. After doing this, shut off the fresh water open a faucet to drain the pressure and flush the toilet waiting for the vacuum pump to stop, Again do this 3 or 4 times.
2) Next winterize your Fresh Water system, You have a few choices, Non Toxic propylene glycol antifreeze, Compressed Air and I have even heard of people using gravity. The first 2 listed would be my choice. While opening each fresh water connection to allow anifreeze or air to come out, then closing the connection, go step on the foot pedal and allow either antifreeze or air to go through the water valve and the vacuum breaker, with the anifreeze you'll see it in the bowl, with air you will see a small amount of freshwater and the you will just hear the air.
3) Now your ready to winterize the toilet, vacuum tank and vacuum pump, Pour a couple of gallons of Non Toxic propylene glycol antifreeze into the toilet, flush it, allowing the vacuum pump to shut off, Do this a few times YOUR DONE.
4) Now would be a good time to get he waste tank pumped out, If you have a access to fresh water add water back into the waste deck plate and pump out again, This will dilute whatever waste is sitting in the tank. You will never get all the waste out of the tank, You can pour a couple of gallons of Non Toxic propylene glycol antifreeze into the waste deck plate.
5) If you have a waste discharge pump, now would be the time to turn it on and the antifreeze that you poured into the waste tank will circulate thropugh the pump, It's going to be somewhat diluted but should be sufficient.