Bloomin eck. Just had a very informative presentation from one of our local council EHO's on Legionella. Lot of scary stuff about water tanks. I'm still of the opinion though that as long as I sterilise a couple of times a year and drain down if it not going to be used for more than 12 days ( and after winter trips ) I should be ok. Not wanting to scare anyone but it might be worth looking into it so you know you are taking reasonable precautions for your own peace of mind. I do think if I was fulltiming I would probably never bother sterilising as the water would never be sitting long.