Originally Posted by MattL
Very good, thanks Shrew
As far as winterizing the head, can I just flush some antifreeze and then pour some down the pump out deck fitting?
You will absolutely need to pour antifreeze (propylene glycol) down the head and flush back to the holding tank. You'll want enough to ensure you've displaced an water in the line between the head and the tank.
The pump will always leave something behind. You'll want enough to ensure there is enough in the holding tank to keep anything from freezing.