In reply to Frankie boy:
When you say "travelling" I assume you mean to foreign climes?
I've used the Steripen (there was a review on here a couple of years ago so do a search) which uses UV to zap the nasties. It doesn't remove particulates though so you may need a physical filter as well if the water is particularly turbid.
In this country, I've never bothered, in fact our house supply is untreated. I find a lot of tap water undrinkable, unpalatable may be a better word, even though it's "safe".
ALC