At first decided to stick with tap water on the basis that I was lucky to have clean water at all. But looking into it it does seem that the cryptosporidium parasite is always a possibility, including in some filtered and bottled water. I wonder if anyone has identified water that is purified to eliminate crypto. According to DAFRA tone sure this water must be treated by reverse osmosis or distilled. Any thoughts before I go and peer at every bottle in Sainsburys?