Quite a few years ago I lived on a farm in the mountains – good old days. We had water running straight from a mountain steam, through a wire mesh into a water pipe. We had it tested and it almost had no ecoli. Nothing added it run straight into our taps with gravitation. The stream did not even run dry during winter. We did not even have a water tank. Except if the water pressure dropped or it started tasting a bit sweet. We would walk up the mountain to find the wire mesh (somewhat of a filter) is gone. That replaced we start opening the ‘T-junctions’ in the pipe to find the frog… !
If the water was muddy the bush pig got lazy and bit straight through the pipe – we would walk up following the pipe line, listening for the hissing sound of either the water from broken pipeline or puff adders.

My info is in Afrikaans, Mountain Biker. Maybe this link will be helpful http://www.i4at.org/surv/watersup.htm