Questions from Stokey12

hi everyone, im going to ask all the questions that are niggling away at me rather than doing a thread for each question as i dont want to swamp the board.  If you could give me the answers id be very grateful.

my caravan is an avondale dart 475/4

1.  when i turn my water on and plug the water pump in will it automatically fill the tank for the hot water to the shower/sink etc, because I dont want to turn my water heater on with no water in the tank to heat up and damage the element

2.  how often do i change caravan tyres?, my dealer told me every 7 years is this correct?.

3.  i have a mulitimeter to measure whats left in the battery.  Is it 12.8v fully charged and 12v empty?

4.  can you use normal toilet paper in the caravan or do i use a specific type?

5. do i leave the water pump on all of the time we are on site or just flick it on when we need to?

6.what size gas bottle do i buy, is it 7kg?, i want the biggest one i can fit in?

thanks very much