Yeah took water from mountain streams for years with no ill effects. I have used a filter for lower water even dirty puddles when desperate, which has been ok.Most of the warnings about filtering water in the uk, originate from companies selling filter systems, just as health warnings originate from pharmisutical companies and the like.Despite the best care we took, we did fall victim of Asian Cryptospiridium while in Nepal, came back home with it after 3 weeks away. After trip to GP, enviromental health came to our house (no warning, just turned up) to satisfy themselves that the source wasn't over here. Cleared after the usual 21 days self limiting period, but sore abdomen for almost 6 months.