Drink Safe Systems Travel Tap
5 stars, but if you're in the UK hills, you could…
Price Paid: GBP 35
5 stars, but if you're in the UK hills, you could leave home without it — you just might have to carry more water if passing through farmland etc.
Filter and drink as you go (and save on bottled water in towns) in the hills, especially if you are afraid of drinking bugs. We usually just drink from mountain streams in the UK but decided to try this in the developed areas we were passing through and it weighs only a bit more than a bottle. The advantage in our situation was that we didn't have to carry as much water during the day.
The disadvantage is that this leads to a bad habit, where you end up on the ridges with not enough water and have to descend for more - so adjust your methods accordingly. It can also lead to a curious situation where all water becomes suspect (see below).
Pros: drink and go (the modern way!)
Cons: can lead to a false sense of insecurity, known as "Bourgeois Paranoia", where everything becomes unsafe because you forgot why and you need an expert's opinion anyway.
Other uses: squirting a H2O circle around your used (off to one side) toilet paper before you burn it (if that is how you roll), so that you don't set fire to the lovely countryside (it wasn't me).