I use a little MSR miniworks filter pump, its pretty small and light and does the trick. Flow rate is nothing like what you are led to beleive though, it takes about 10 mins to fill my 2 litre bladder, whcih conviniently screws directly onto the filter. My bladder is a source one, and MSR deromatory bags fit too, not sure about others.

I have no personal experience with tablets, but prefer not to use them, and I hate chemical tastes anyway, hence the filter.

If i were to buy again though, I would pay he extra money for the steripen, which I'm sure someone can link to s I dont have the address, that thing looks/sounds awesome, and I think I would hav gladly payed the extra 60 quid for it rather then my MSR

Here's a link for the Steripen. It's a fantastic piece of kit, far, far easier, quicker (1.5 mins  to process a litre of water) and less hassle than any filter system or tablets, and it doesn't alter the flavour of the water at all. Make sure you take a spare set of batteries though.

Also, you will need a wide-mouthed bottle to be able to use it - eg the Nalgene type. For a very light, Platypus-style wide-mouthed bottle, take a look at the Nalgene Canteen. The 1.5l version weighs all of 64g.

Also, if you have to take water from, say, a pool rather than clear fast-flowing stuff and there are physical bits in it, it's best to filter these out first by pouring through a piece of microfibre cloth - we use either a Buff or a small square cut from a microfibre towel.

I have to say, after using one of these, there is no way I would use a filter pump / tablets.

Hope that helps.

You do not need a wide mouthed heavy Nalgene bottle with a Steripen; try chopping an old 2 litre platty in half and use that (17g)

I've been using a steripen this summer, and it's certainly easy to use. However, I have one reservation - that it only treats the water *in* the container, not any water on the lid or threads, leading to possible contamination. This isn't an issue when you're filtering water into a bottle from another source and, when using chemicals (e.g. iodine), one is generally supposed to loosen the top and shake the bottle 5-10 minutes into the treatment.

Not entirely academic - I'm now two days into a serious dose of the squits, with no obvious recent contenders, which has me wondering whether I've picked up something with a delayed effect such as giardia.

Consider a Millbanks bag as a simple filter, although they can be a bit slow.

By the way, I wouldn't bother filtering/treating water high in the Lakes myself.

I have tried the katady 'hiker' and MSR miniworks.  The miniworks is a great bit of kit but the ceramic core is easily broken if you drop it when you have to clean it(I did this)

The katadn has a much faster flow rate, probably nearly twice as fast as the msr!  It does not look so cool though. 

Do you really need to filter the water?

I have never bothered.  In 35 years of drinking water on the fells, have never suffered any adverse effects.

I switched from filtering when I found that I got so cheesed off with sitting by a stream/pond pumping away at the end of a tiring day! Have used AquaMira drops for a while now and they are superb: quick, no aftertaste and no medical danger (iodine is not safe for long-term use for example). Highly recommended.

If you happen to go to other countries where you need to use quite bad water sources, you can pre-filter using a clean tshirt or whatever before treating. Should not be needed in the UK.

I've drunk plenty of unfiltered/untreated water in UK hills in my time, but for the sake of a little hassle I'd now rather be safe than sorry. Pollution of upland sources has increased, and when you're knackered you may not walk quite far enough up the stream to find the dead sheep.

(Actually, on one trip in Scotland, I went to the stream, tasted the water before sticking it in my bottle and thought "Hmmm". A couple of minutes later upstream there was the archetypal dead rotting sheep, slap in the stream. Needless to say I got my water from elsewhere. But why do they go to streams to die? Do they hate hillwalkers that much?)

Ive got a steripen and think its great.

at the begining of september we went wildcamping and i took it with me along with the pre filter and bottle, I used filled the bottle, steripenned it then tipped the water into my camelback...worked a treat and took no time at all.

one thing to watch for is that my mate bought a naglene widemouth and for some reason the prefilter doesnt fit on it as well as it does on the steripen one...dont know why as its identical.

i bought a  couple of naglene style  bottles from aldi for £3 which it works perfectly with too.

The steripen is certainly quick and easy, but how do you know it's great? Wild camping in the UK hills does not, in my opinion (and others), generally require the use of water treatment. You could equally just fill the nalgene bottle and pour it, untreated, into your camelbak - you're little more likely to get sick.

It's for overseas use that you need to weigh up the pros and cons more carefully. I'm not sure I trust mine enough when the water is of a very dubious quality, for reasons stated above.

we i guess knowing it works woudl be the same for any filter/treatment, UV is a tried and tested method with the waterboard so i dont see why it wouldnt work with the steripen.

as for it getting cranky when cold ive not had this problem, i used rechargable nim h batteries in it...the same as i do in my gps as that didnt like being used in the cold with standard aa batteries.

Im not trying to say the steripen doesnt have drawbacks like you mention with contamination on the lid but for use in the uk its gotta be pretty much ideal.  and if you are really worried about getting ill then boiling/chemicals could also be used.

Chemicals aren't available where I live; batteries are. Boiling consumes fuel - not good if there's no means of resupply and you're carrying a large load already. I've chosen the Steripen because it's the best option for me outside of carrying a filter pump (which I don't want to do, for various reasons). However, I think one should recognise that there are potential problems with its use outside of a lab environment.

Again, in the UK I personally wouldn't bother with water treatment, despite the possibility of dead sheep round the next bend.