Always travel with full tanks, never know when you might need it as we would rather free camp. It is a pity to use tank water to flush the toilet. Might add we have never filled the toilet, I always use the bush for no 1's and we only shower every other other day which helps the water go a long way. We are only 2 people so I would expect a family would use it up a lot quicker. with cleaning, we only rinse it out. I suppose you could use silcone grease on seals as you do with a swimming pool. Don't the chemicals do great job, abley assisted by the motion of the van on the road