Water purifier- which one to buy?

http://www.tcinz.co.nz/images/BerryBin-Images/SwiggyRange.jpg The swiggy cup has been standard issue in New Zealand pretty much forever. As long as the water is clear and not stagnant or turbulent and has not come from farmland it is enough. The only 2 things to watch out for are giardia and cryptosorosis which are common enough bugs world wide. Take your water carefully and you are fairly safe but although for us getting caught out for us would be a few days off work it can ruin a holiday

I use a Sawyer Mini filter, about 50 grams I think, and only US$25, small, you can carry it with you all the time, and it will last a lifetime (1 million litres), provided you don't let it freeze overnight (I blow in it to remove any water, and put it in a ziploc with me in my sleeping bag when it's cold). There are three ways to use it: like a straw to drink directly from a pond or a stream, by screwing it on a standard plastic bottle (like Coke bottles) that you will squeeze to get water or at the end of a hydration pack hose. With a hydration pack you can use it either as a straw (just suck water from it) or as a gravity filter like me: just attach the hydration pack to a tree and let the water drip in another hydration pack or a bottle. It takes about ~5 minutes to filter 1 litre of water, I do it during breakfast or dinner. For me it's the best solution, but NZ water is pretty good, but it's sometimes hard to tell if there might be a campsite/hut/sheeps above that may contaminate the water. Water at huts rainwater/tap water is usually good to drink (when the tap is not frozen). Rainwater is usually safer but may have some ash residue from the hut wood stove that gets washed with the rain. Not really a problem I think unless you live there for months. Worst case scenario: if unsure, boil the water ;)

Boil or filter if you're worried Gizmo. The purification tabs aren't very effective for Giardia.

Also: http://lifestraw.com

+1 for the Sawyer Mini. Light and cheap and yea really will last forever. ALthough as stated NZ is pretty good and I only take it places I think I might need it. Most places rivers/huts are good enough. From what I understand the main thing filters don't do over pills is kill viruses, which seems to be more of a European thing from my limited knowledge. Basically check your water source and apply some common sense and you should be fine.

I've ordered this. Haven't got it yet, so can't attest to how good it is or not, but it's very adaptable. I like the look of it, so I bought it. http://renovowater.com/index.php/muv

Gizmo, it depends a bit on your cooking style. We use a fair amount of water (I like to get some coffees in the morning, have oats which need water, we like to drink tea), so we have a 2 litre Platypus GravityWorks setup, which works great for us. People who basically only drink water from bottle and perhaps use a bit for cooking seem to be very happy with the Sawyer (and you can get some gravity style setup there too). And obviously you can simply boil your water, that's supersafe, no need for any of the above. Finally I would say you probably can drink water in NZ streams safely, if you don't drink too much. You have one giardia per 20 litres here, and you need to get about 5 to get sick, so about 100 litres. This seems to suggest to me that for one or two days drinking from a stream is fine, for a couple of days you probably want to filter. And filtering removes a lot of other stuff. As they say: your frog sperm may be perfectly safely to drink after adding tablets, but you still drink frog sperm :-)

Never drink downstream from a dairy farm. Just sayin'...

In the back country, drink from the above track side of small streams that cross the track and come down from virgin bush or tussock. Somewhere like the Greenstone or Caples where there are cattle in the main valley, I wouldn't drink from the main river or lower side streams, but you can still find small streams coming down from virgin bush in the places the track sidles higher. You may want to be more careful somewhere like the Abel Tasman where there are less streams coming down from untouched country. Water quality / treating water is much more of an issue in the side country - places you'd tour on a mountain bike or parts of Te Araroa where you're spending a lot of time in country that has stock on it.