Have done the same in Wales and in Scotland years ago when I was in the Military, we just dropped a sterilising tablet in if we weren't sure. Now most of my water is filtered and it's sweeter and better than the tap water in Chester.We have a number of natural springs in the hills around here; there are no water sources above them and I drink from them untreated regularly. I always have done in the welsh hills if I'm high enough up. We're also on our own private borehole and the water is pumped up 100m - it is the cleanest tasting clearest water you will find and totally untreated; I cannot drink tap water from towns and cities - the taste is disgusting.
When I was on a Combat Engineer 1 course part of the syllabus was water supply both bulk and personnel, for the bulk we used chlorination sets with pumps and personal use we use the Milbank bag.
There were certain tests we had to carry out at water sources one of them was to check for the usual parasites etc; but the other was for bone oil. Bone oil occurs in mountain streams especially were there are flocks of sheep. If a sheep dies or falls into a water course and dies it pollutes the water, the bone oil is highly toxic and that was drummed into us, always check the water source in mountains.
I also had a blood test not long ago that looked to see if I had any parasites and pathogens in my blood, the Dr did the full spectrum and the results were negative, because I regularly drink filtered water from our club lakes he wanted to make sure I'd not picked up anything causing me a digestive problem, unfortunately I have IBD as it turned out and wasn't anything I had consumed in the sticks.
Interestingly most water I have come across never had a bone oil problem so it wasn't an issue. The other test we did after cleaning the water was a Neutral red test, this was to make sure chemicals were not present, however, most tap water in the UK is not to Military standard so it always failed and that's water supposed to be clean via the water utilities.