When it comes to drinking water, you want enough and safe enough.
The following is based on the level of risk I am comfortable with for my style of tramping which is (as much as possible) off track in areas with few people or farming. If you're doing Te Araroa the risks are going to be much different.
Volume
I usually carry a collapsible cup in my pocket and one or two two-litre platypus bladders. If I'm heading to the tops to camp without access to water, I might fill both bladders. I have a bad habit of not taking enough hydration stops during the day which increases fatigue - the cup helps with this but for tops travel a drinking tube is useful. I keep ripping the mouthpiece off in scrub though.
Quality
Sources of water when you're tramping will not be as reliably safe as a good town supply. There are many options for making water safer - the following might be of some use in deciding what level of risk you are prepared to take.
To my mind, you want to have some appreciation of the actual risks, make your own choices based on the level of risk you are comfortable with (acceptable risk) - not just follow others' views (perceived risks), and understand how your actions might reduce the risks (residual risk).
First up, you want to be thoughtful about where you get advice on water safety.
- There's quite an industry interested in selling you treatment systems and products
- Those responsible for a water supply (e.g. at a hut or camp site) may under or over play risks based on their fear of being made to install costly treatment or fear of being held to account for lots of people getting sick
- Some are dismissive of risk based on a case study of them and their mates ("We've bin drinkin' outta this pond for years and never got sick")
- Many people have distorted/uninformed views of the relative risks of the nasties that might get into drinking water
- We all have different thresholds of risk that we are prepared to accept
I reckon health and science-based agencies will give the best scientifically accurate information but some may be risk averse in their advice as it needs to work for the young, the old and the immunocompromised. Advice from NZ agencies is a bit sparse but the American CDC has good and extensive info - see links at end.
As usual - the following is just my opinion, so you should filter with items 3, 4, and 5 above in mind.
Types of contaminants
Water can be unsafe because of contamination by bugs:
Viruses: - very small - can pass through most filters, can be killed by chemical and UV treatment. E.g. norovirus, Hepatitis A
Bacteria: bigger but can pass through many filters, can be knocked out by chemical and UV treatment. E.g. campylobacter, salmonella, some strains of E.coli
Protozoa: much bigger and more resistance to treatment - taken out by many filters, may not be taken out reliably by chemical and UV treatment. e.g. Giardia, Cryptosporidium
These are the most likely and significant contaminants. Not all are pathogens (cause disease in people) but if the contamination comes from a human or animal (including birds) source (e.g. faecal waste near a waterway, farm runoff, or feral animals) it is more likely that pathogens will be present.How serious and how likely?
While you are not likely to get cholera, some of the infections you can get are extremely unpleasant - and some are very easy to pass on to other people.
Campylobacter for example, can present with acute pain akin to appendicitis and have long-term sequalae, and norovirus can rip through a series of tramping huts ruining everyone's holiday.
So, before believing people that tell you they've never been sick in twenty years tramping, or that it's only a dose of the trots, bear in mind:
- Incubation periods vary hugely so you could be debilitatingly sick in a matter of hours, or succumb weeks later (don't accept statements that you will be out of the bush before getting sick).
- Given that symptoms can appear a long time after exposure, I simply don't believe peoples' memories are reliable enough to be sure they haven't been sick three weeks after a tramping trip at any time in their life.
- Most people don't have many clues about attribution - e.g., people will often blame illness on a recent meal ('I knew that burger was dodgy'). But incubation periods vary hugely between pathogens and people, so an infection could be from the burger, another meal, from another person, hand hygiene ... or something you drank a fortnight back.
- Anecdotes based on personal experience is the weakest form of evidence (but has a disproportionate influence on what we believe to be true).
- While many cases might be dismissed as a 'dose of the trots' infections can be severe and long lasting - people have required rescue.
- These diseases are faecal-oral (yes, that is as disgusting as it sounds) so you become a risk to others. You're not just taking risk on your self but can pass infection onto family, friends and other trampers - even if you have no symptoms.
Appearance and taste
The appearance, taste and smell of water (organoleptic quality) can also be affected by various things without making it unsafe. Think the tea-coloured streams on the West Coast from plant tannins, brown iron staining, and even sulphur smells from some chemical reactions (not to be confused with a dead possum in the water tank).
Treatment can also affect the organoleptic qualities of water (see below).
Sources of contamination
Contaminants can get into water:
- at source - e.g., farming, wild animals, industry, other trampers, septic tanks, birds on the roof, geothermal activity, surface run-off into a well, minerals naturally in the water ...
- during any treatment, storage and reticulation - e.g., poor hygiene and not following treatment process instructions, materials used on roofs and pipes, uncovered storage, pests accessing storage containers, bad connections - e.g., backflow from stock troughs), chemicals used to clean tanks, overdosing treatment chemicals ...
- at the point of use - e.g., dirty bottles, cups, hands, taps ...
Water sources
This is pretty rough but in order of risk ...
- City supplies and secure, deep bores are the safest sources but you're unlikely to see many of these when you're tramping.
- Smaller council supplies should generally be pretty good but can be a little variable depending on the competence of the council - they will at least be tested regularly and should be managed by someone with a few clues (with some notable exceptions).
- Small private and domestic supplies may have their own treatment systems (e.g. UV) these are as good as the knowledge and abilities of those running them. The odd one might be tested but not at any frequency that gives statistical confidence.
- Shallow ground water (e.g. wells and springs) can be ok but are best assumed to be at risk of contamination commensurate to where the water has come from (e.g. a nearby river) and local sources of contamination (e.g. surface water around a hut entering a well). These can be poorer quality than rainwater, e.g., as there may be farm or human contamination.
- Rainwater will contain bacteria and sometimes will be very poor quality depending on what has crapped on the roof or died in the tank, it is less likely to be affected by human waste unless something weird is going on (e.g. a ground water tank too close to a long drop). It can be a bit smokey from some huts.
- Surface water is generally the least safe - there will always be bugs in it, there will often be pathogens, and these will sometimes be at infectious concentrations (which are very low for some bugs). Quality will depend on what's in the catchment - even pristine bush catchments and alpine streams will be affected by animals. Any farming and other human activities significantly increase the risks. Rain will wash contaminants into water ways and murkiness (as opposed to colour) indicates material in the water that bugs can hitchhike on.
Treatment options
None
My preferred method. I carry water 'purification' tablets but rarely use them and don't carry a filter.
This increases the risk of getting an infection (I've had symptoms once or twice but it's hard to say whether this was the water or something else).
I will generally drink roof water without treatment unless I have suspicions (e.g. rat or possum sign, heaps of bird poop on the roof).
When it comes to surface water my ideal is visually clear water from a pool in a small stream upstream of human contact (like a track). I avoid catchments that might have human activity - (farming, roads, houses, huts). In busy areas I try to avoid catchments that have tracks, campsites and swimming holes. If the water is turbid, it will likely have more bugs, and I try to avoid stirring up sediments as these are more likely to contain pathogens.
I prefer smaller streams purely based on my assumption that the larger the catchment, the greater the potential for contamination (e.g. if following a stream I'll look for a side stream). Sure, a dead goat in a small stream will not have as much dilution as in a larger catchment, but an infected human or animal can shed billions of infectious units, i.e. a twice as big stream may mean half the concentration of goat bugs but it is still a very big number - and there's double the area for goats to die in.
I look for a pool as protozoa, being heavier will settle out along with larger particles that might be carrying viruses and bacteria.
I'm wary of water in tarns and ponds on the grounds that turnover might be limited so any contamination could hang around (e.g., from a deer standing/crapping in it). Lakes do have the effect of allowing particles including pathogens to settle and UV from sunlight to kill bugs at the surface - I'm not so keen though if people are swimming or camping nearby.
If you know you'll be traversing an area where water might be dodgy (e.g. crossing farms) or scarce (e.g. tops), having a bit extra carrying capacity is useful so you can top up from a cleaner source before hand.
Where I'm not so sure about a water source I will use purification tabs (follow the instructions) or (rarely) boil it. The protozoa Cryptosporidium is relatively resistant to chemical treatment and various things can reduce the efficacy of treatment chemicals so I'm conscious that this does not eliminate risk.
DOC has warnings about not drinking water at most of its sites. This is a sensible, precautionary approach given that with so many it's not practical to assess the risks at each site which will vary between sites and over time with the nature of source, animal populations, number of people visiting and how they behave. Further, if contamination occurs it could affect a lot of people, so the overall consequence of contamination is higher than one person deciding not to treat their water. I will generally check the supply out and if it looks ok drink the water without treatment given that it is just me that might be affected.
Boiling
Bring to a boil for a minute and let it cool. Some references and signs say boil for three minutes - this is over kill and a waste of fuel. You are not fully sterilising the water (this would require temperatures above 120 degrees Celsius) but you are making it safe to drink. Boiling is effective for viruses, bacteria and protozoa but not most chemicals. Boiling has obvious draw backs of fuel and time requirements and needing suitable containers for cooling a sufficient volume.
I suspect that even just bringing the water to the boil significantly reduces risk - e.g., think about the temperatures involved in pasteurising milk.
Filters
Filters that remove particles based on their size will be effective against protozoa if they remove particles over 1 micron. To remove bacteria, you are looking at something more like 0.1 micron. Read the fine print though - numbers representing effectiveness do not necessarily mean that all particles above that size are removed. You might see references to absolute (filter pores are that size or smaller), and nominal (reflects average pore size so larger particles will pass) and most advertising will refer to things like 99.999% removal of xxx. I suggest looking for certification from a reputable standards organisation and read the ad blurb carefully - cheap, over-hyped, very high flow rates, and lack of care requirements (backflushing etc) could indicate a filter is not all it's cracked up to be. You should expect a filter to take time to operate and to block over time - the dirtier the water the faster this will happen.
Many filters will not reliably remove bacteria, and most will not remove viruses unless they have additional treatment (e.g. chemical or UV). If a filter doesn't reliably remove bacteria, I would want to use a chemical treatment as well (on the grounds that there are many bacterial pathogens you can get from animals). However, bugs tend to hitchhike on particles, so by reducing the number of particles in water, filters will reduce loadings of bacteria and viruses and given that human pathogenic viruses are less of an issue from animal sources a filter that is good against bacteria without additional chemical treatment may reduce risk enough for your piece of mind.
I've heard of people using coffee filter paper and clean cloth to reduce turbidity before chemical treatment. But, it doesn't take many units of some pathogens to infect you, so I see little point in using low quality filters on their own.
The US CDC has a useful page on filters.
Filters with activated carbon
These will likely be advertised as removing various scary chemicals. I wouldn't bother - you should be avoiding water sources subject to chemical contamination (e.g. affected by farming) anyway. Carbon filters can apparently be a good medium for growing bacteria so may end up reducing quality.
Chemical treatment
Chemicals require the right time and conditions to be effective. Protozoa are more resistant to chemicals - particularly Cryptosporidium, and organic matter in the water will use up the active ingredients leaving less ability to kill bugs. Some chemicals will leave tastes and odours - at the extreme this may affect palatability to the degree that you find it difficult to drink enough. You can help mask this with a drink (like raro) or electrolyte powder.
Purification tablets and solutions
Read the blurb to determine how effective the product is against the three types of microbes. I would favour products that produce Chlorine dioxide as it is recognised as being able to knock out Cryptosporidium (at the right concentration for the right time).
Be careful to follow the instructions - particularly waiting time before drinking (contact time). I read somewhere that 2ml of hydrogen peroxide will treat 3.7 L of water. I wouldn't recommend it as it's a very hazardous chemical to be lugging around.
Iodine is also used but not recommended for some people. I used it overseas on a trip and found the taste off-putting.
Bleach
Household bleach contains sodium hypochlorite which at the right concentration will knock out most bugs but is not effective against Cryptosporidium - it is also generally not effective against chemicals (with a few exceptions, e.g. iron in some circumstances). If the water is dirty or highly coloured it will be less effective, but you can up the dosage. Combined with a pre-filter capable of knocking out Crypto you'll get a pretty good result.
You want bleach that is unscented and from a fresh bottle as the active ingredient will reduce over time. You don't need much - the Ministry of Health recommends 5 drops per litre with 30 minutes standing time for drinking water in an emergency. This will give you a much higher concentration of active chlorine (about 13ppm) than in a typical water supply (less than 1ppm) but it gives leeway for organic matter in the water that will use up the chlorine and will have some affect against protozoa (Giardia but not Crypto). You can work out your own concentrations using the following formula:
Volume of bleach = (Desired final chlorine concentration as % x 1000) / Concentration of active chlorine in the bleach as %
E.g.: 0.05ml = (0.00025% x 1,000)/5% Or: 1 drop (0.05ml) of 5% bleach in 1L of water gives 2.5ppm.
5% is probably about the right concentration in fresh bleach in NZ but it will vary - you should be able to find the % Sodium Hypochlorite on the label somewhere. 0.05mml in a drop is somewhat approximate of course.
Ultra-violet light
In theory UV is good against bacteria and viruses but not so good for protozoa. Effectiveness is decreased by anything that stops the light penetrating through the water (e.g., coloured or cloudy water) and if the lamp starts to get dirty. UV has no impact on chemical contamination. Be careful about marketing that glosses over kill rates for Crypto and the need to prefilter if the water isn't clear.
Sunlight has enough UV to kill bugs but I think there are too many variables to rely on it. Clear water in a transparent plastic bottle left for some hours in direct sunlight can kill bugs but you need to do your homework to make sure you're doing it right. UV on a water surface will also have some effect, I suspect it might have some significance at the surface of a lake but I'd be dubious about streams given all the other factors influencing bug loadings (e.g. turbulance moving bugs below uv penetration zone and entraining sediments, sources of contaminants ...)
Magnets, crystals and colloidal silver
Quack.
It has been well known for a long time that silver has bactericidal properties and you will find it in some bona fide treatment systems. A quick google search though throws up a lot of quackery and vague claims around it, I'd exercise a bit of scepticism about miracle claims and would look to see it used it in combination with other treatments by reputable companies.
A few references
The US Centres for Disease Control have some really good pages
The Hiking the world blog looks credible to me and references good sites
NZ Wilderness mag has some information although not as good as the above two:
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