Being blessed with an iron constitution and burdened with a cavalier attitude to personal safety means that I've never really bothered with any form of water filtration or purification. I've never suffered any ill effects from drinking straight out of streams, rivers and lakes. Obviously I use common sense when sourcing water ... only taking water from fast flowing streams, checking for dead animals upstream, collecting water away from paths, etc.
A few weeks ago I found myself in a position that made me reconsider things a little. We (Taylor, Steve M and myself) found ourselves in a Welsh forest in the rain, which in itself isn't very unusual. What was unusual was the fact we were struggling to find a source of water, no rivers, streams or springs. The forest in question was however about the wettest, boggiest forest I've had the pleasure to sleep in. The only (just about) running water source we could find was in a drainage ditch!
My super sense of, 'tasting for nasty water' led me to believe the water we'd collected would be fine to drink, even if it was brown but you could be easily mistaken. To cut a slightly long story short, we did drink the water and no one died but we'd filtered the water first! As luck would have it Taylor had brought along a Platypus gravity filter and everything we drank went through that.
Water good ... Sheep poo bad
Yesterday while walking around the outdoor emporiums of Betws I came across this water filter. It filters out 99.9% of Giardia and Cryptosporidium, both of which would end anyone's ride very quickly. You can use it in-line in conjunction with you normal bladder or screw it onto a water bottle or platypus pack. The filter is good for up to 50 gallons before it requires changing and the best bit is, they're selling them for £15 at Cotswold Outdoors. It's small enough to loose in a pocket and weighs 50g so there shouldn't be any issues with packing one. There's a few of these on the market from different manufactures but I've never seen them at this price, so if you've any concerns about whether the water you find is safe to drink it might be a sound investment.
Don't think that you need a filter for the WRT though, you shouldn't have any problems finding clean, safe water, as long as you're sensible ;o)