this is our first winter with a caravan - we have a 92 swift 450 and I have just drained the water via the side thingy by the flue (i think)- do i need to empty the toilet and all the components or will any of the chemicals used act as an anti-freeze ? i know i need to power up the van to flush the toilet, but now i have emptied the water (via the side thingy) will this cause any problems as the pump will operate empty.....if you see what i mean (dont you just love novices !!)