That is quite a statement to make! Especially to the uninformed!
In wild country areas - what you have said is probably true (most of the time), but for "most water sources in the UK" (sadly) it is not. Filtration removes particulate matter only. Purification (either chemical or by boiling) should be a matter of course before consumption. Just looking at the map to see what is in the area may not be reliable (a heavy downpour of rain twenty miles away can cause a storm drain to overflow, run down a lane, into a ditch , which then flows into a gully, that flows into a stream (fed by a spring) - where you are collecting water!
I contracted gastroenteritis under these circumstances many years ago - a mistake not to be repeated!
Water is a requirement for life, so every precaution should be taken.
If you require advise talk to someone who knows - Leon1 (my brother) has been tasked with providing safe water for extended periods for groups up to battilion strength.
Hope this helps
Neil
Apologies for being misleading with the "Most water sources" comment. I simply meant genuine sources, such as springs and direct runs from them. Never in my experience have I ever come across a gully leading into a stream at source, or within a few hundred feet of them. Also the likelihood of a storm drain overflowing and reaching such a water source is incredibly remote. It would have to evade every other drainage system in place, between it and the stream/gully, make it across land that acts as a soak-away, retain it's concentration through the entire process, and for you to be unlucky enough to be at the receiving end. I agree that in times of severe flooding, this could happen, in which case all water within 20-30 miles would have the possibility of contamination.
On the matter of filtration, I did say (
in this post)that it removes all debris, which is particulates and upward. If you are going to the trouble of filtering the water, you obviously believe there is a need to purify, so I assume boiling or puritab will follow that.
The last consideration is, many of us "outdoorsy" types have reinforced immune systems for mild contamination (at least if you spend any amount of time getting dirty and burying your excrement with a folding trowel
), so the risk of intestinal disturbance is greatly reduced. I was sleeping in puddles and drinking ditch (well near enough anyway
) water 12 years ago in the Anglians, never suffered gut rot then, only with the end-ex curry haha. People sometimes drink from the hot tap in their houses, which comes from the tank in their loft (or other, if in a flat). These tanks contain dead insects, dust, dirt, debris, sometimes dead rodents in old buildings.