For when the water just doesn't look like it came out of a tap.
Water treatment is an often-overlooked necessity. Almost all water you work with while tramping is potentially contaminated. What we are worried about is:
Protozoa - parasitic organisms that cause intestinal problems, these are the most common problem with drinking water in NZ.
Bacteria – another potential problem in NZ, but very easily filtered out.
Viruses – not really a problem in NZ, but a significant problem in other places around the world, particularly third-world countries.
There are four main types of water treatment typically used by trampers, and each have their pros and cons:
Boiling – easy to do, doesn’t require special equipment, and will eliminate all of the above problems. BUT on the downside boiling water during a trip is incredibly inefficient: it uses a lot of fuel, and takes a lot of time. Really only practical for treating small volumes of water.
Chemical treatment – possibly the easiest and cheapest method in the short term. Small boxes of tablets can be bought cheaply and when a tablet is dropped into water it will eliminate almost all of the above. But it will take hours at quite high concentrations to eliminate certain types of protozoa, which can negatively impact the taste of the water. Always check how long you need to leave a tablet in the water to eliminate all contaminants. For example, tablets can sometimes take 4 hours to eliminate cryptosporidium. Can be good for treating small and large volumes of water.
UV light emitters – Will deactivate all of the above but only if the water is clear, so you often have to filter the water first. Also quite expensive initially and requires expensive batteries to operate. Good for small to medium volumes of water, but doing more than a few litres at a time can be tedious. For example, have a look at a SteriPEN.
Filters – a good filter will filter out all protozoa and bacteria, but not viruses. More expensive than chemical treatment in the short term, but will not negatively affect the taste of the water and are much faster to use. Even though it will not eliminate viruses, viruses are not really a problem in NZ so this is less of a concern. Depending on the filter, they can be good for treating small to large volumes of water. For example, the Sawyer Mini Filter is great for treating small volumes as you go (you can screw it onto a water bottle). The Platypus GravityWorks Filter is excellent for treating larger volumes of water.
Really it comes down to personal preference. Chemical treatments are the cheapest in the short term, and very effective, but you have to deal with the taste. If you are going to go traveling to places like India or South-East Asia, you may want to invest in a UV light emitter. But if you are mainly going tramping in NZ, I would recommend filters, they’re quick, easy to use, light and relatively affordable.