Safe/Unsafe Drinking Water

[JoshT]

Lots of good information in this thread, but a few red herrings too. A few points to consider:

- Surface water in streams is naturally low in salts, chemicals, metals, petrochemicals etc. Any presence of these comes from human interaction.
- There is almost no useful way of measuring water safety - identifying risks and treating appropriately is the only way to ensure safety.
- Any water downstream of humans should be treated with caution.
- Anecdotal evidence that 'I didn't get sick' doesn't mean water is safe. Every gut is different. Around 40% of people are susceptible to certain gastro bugs, others aren't.
- After heavy rainfall, any water source near humans should be considered unsafe. Sewerage systems are designed to overflow into creeks and rivers during heavy rain.
- Metals and chemicals are usually only toxic in very high concentrations which are highly unlikely. You need long term exposure for any health impact.
- A TDS meter (actually an electrical conductivity meter) will measure one thing - electrical conductivity. This is basically a measure of saltiness and isn't that useful on it's own.
- Elevated EC in stream water (anything above about 400) indicates water has an additional source; either mine discharge, tidal seawater influence, urban runoff, etc. Indicates higher risk.

On treatment
- Boiling kills anything microbiological. Rolling boil is all that's needed, not for 1 minute or 5 or anything.
- Filters remove bacteria and dirt, but don't remove viruses
- Viruses are killed very quickly by chlorine and other chemicals
- UV kills anything microbiological but only if the water is clear - dirty water needs physical filtration first
- Chlorine (and most other chems) kills everything except cryptosporidium (watch out for humans or cows). Also needs clear water.
- Activated carbon removes tastes and smells, and some organic chemicals, but you can't tell if it's effective or not, or when it has exhausted its treatment capacity.

I use a Sawyer squeeze, and add half a chlorine tablet where there is a risk of viruses.

Happy to discuss / be challenged on any of this.

- Josh

[Xplora]

Lots of good information in this thread, but a few red herrings too. A few points to consider:

- Surface water in streams is naturally low in salts, chemicals, metals, petrochemicals etc. Any presence of these comes from human interaction.

Heavy metals and chemicals will settle to the bottom of a stream bed and usually embed in the sand but can be disturbed with increased flow or people walking in the stream. Water below old or current mines would be suspect for this.

- There is almost no useful way of measuring water safety - identifying risks and treating appropriately is the only way to ensure safety.

There is no way to measure water safety in the field. Treat all water as suspect and treat all water if you are concerned. While it may be obvious that some streams are suspect, making an assumption any stream is OK is really a matter of chance. It may be lotto winning number chances but even our so called pristine mountain streams carry protozoa, bacteria and parasites. e.g. Wild dogs carry tape worm.

- Any water downstream of humans should be treated with caution.

Which means most of the Sydney basin.

- Anecdotal evidence that 'I didn't get sick' doesn't mean water is safe. Every gut is different. Around 40% of people are susceptible to certain gastro bugs, others aren't.

Those who are less affected like to tell others which water is safe to drink.

- After heavy rainfall, any water source near humans should be considered unsafe. Sewerage systems are designed to overflow into creeks and rivers during heavy rain.

Urban runoff is just as bad as sewerage overflow. Heavy rain without overflow will increase the risk.

- Metals and chemicals are usually only toxic in very high concentrations which are highly unlikely. You need long term exposure for any health impact.

This is true but some stay in your body for life so long term exposure is possible if you are a frequent drinker of this water.

- A TDS meter (actually an electrical conductivity meter) will measure one thing - electrical conductivity. This is basically a measure of saltiness and isn't that useful on it's own.

Partly true. A TDS meter does measure electrical conductivity as I mentioned previously but it not just measure saltiness. It is a measure of the positive and negative ions. It does not give any indication of what these ions may be but not all are salts. To say it measures saltiness is misleading.

- Elevated EC in stream water (anything above about 400) indicates water has an additional source; either mine discharge, tidal seawater influence, urban runoff, etc. Indicates higher risk.

For those concerned this could be helpful. I don't carry a TDS meter with me while walking but if people are concerned and do not have information about the area then it could be of benefit and as you say it will indicate a higher risk but cannot identify the risk.

On treatment
- Boiling kills anything microbiological. Rolling boil is all that's needed, not for 1 minute or 5 or anything.
- Filters remove bacteria and dirt, but don't remove viruses
- Viruses are killed very quickly by chlorine and other chemicals
- UV kills anything microbiological but only if the water is clear - dirty water needs physical filtration first
- Chlorine (and most other chems) kills everything except cryptosporidium (watch out for humans or cows). Also needs clear water.
- Activated carbon removes tastes and smells, and some organic chemicals, but you can't tell if it's effective or not, or when it has exhausted its treatment capacity.

I use a Sawyer squeeze, and add half a chlorine tablet where there is a risk of viruses.

Happy to discuss / be challenged on any of this.

- Josh

- A rolling boil for 1 minute is all that is required unless above 2000m. That is because water will boil at a lower temperature as air pressure drops. see
http://www.health.gov.au/internet/main/ ... i2209j.htm
- Filters also remove protozoa such as giardia and crypto. Membrane filters can remove viruses but this is not practical in the field.
- Not keen on drinking muddy or turbid water so filtration would be a must anyway.
- Chlorine and iodine are considered safe for humans in small doses but you will be able to taste it. A couple of drops of the iodine carried in your first aid kit (5% tincture) would treat a litre of clear water but double that for cloudy. Add a sachet of ice tea for flavour. Humans, cows, deer, possums, kangaroos and most native animals can transmit protozoa. It has been accepted that only two variants of the crypto protozoa will effect humans. A new type of crypto has been found in pigs which may also affect humans. Wild pigs are prevalent in many areas now.

Some info from MSR
https://thesummitregister.com/water-fil ... urifier-2/

Good input Josh.

[JoshT]

Thanks Xplora for these additions. I'm wondering if a few of us might think about getting together and preparing a fact sheet on this stuff? The thread is good and all, but a proper resource could be useful.

A rolling boil for 1 minute is all that is required unless above 2000m. That is because water will boil at a lower temperature as air pressure drops. see
http://www.health.gov.au/internet/main/ ... i2209j.htm

This is quite an old source, published in 1998, citing a 1993 paper. Current guidance from the World Health Organisation (and repeated in the Australian Drinking Water Guidelines) says a rolling boil is sufficient. Any pathogens likely to exist in Australian water supplies are killed within seconds once temperature gets above 90 degrees, so there's no need for the additional time. Increasing the time is necessary at high altitude as the temp drops, but not relevant to Australia since we don't get that high. http://www.who.int/water_sanitation_hea ... _01_15.pdf

A TDS meter does not give any indication of what these ions may be but not all are salts. To say it measures saltiness is misleading.

Fair enough, though the point still stands that I don't think a measurement of TDS or EC is useful for indicating safety in the field. Main use is for ongoing monitoring of particular streams over time, where a change can indicates a source of pollution.

Add a sachet of ice tea for flavour.

Need to be a bit careful with this, as ascorbic acid (vitamin c) removes iodine. Need to ensure you've had appropriate contact time before adding it. Also as a side note, anyone know where to buy ice tea sachets these days? Haven't seen my usual Nerada ones at the supermarket this year, or Staminade for that matter.

[Xplora]

Josh - I think you have a pretty good handle on this stuff. My partner and I prepared and delivered a talk on this stuff many years ago to staff working in the outdoor industry but things have changed. Principles have not though. I doubt I even have a copy of it now. We now have 3 devices for treating water depending on where we are going. Getting Ice Tea is hard. There are other substitutes but that was so convenient.

[tom_brennan]

Treatment of water or carrying a TDS meter is all a personal choice and if it concerns you then you can take whatever precautions you see fit. The fact is nobody can tell you any drinking water is safe and all water in the Blue Mtns I treat as suspect. There are just too many people there now. The runoff from Springwood Creek and Wentworth creek into the Grose is interesting to watch after heavy rain. Some people can drink from the Cox's river with no ill effect and others can't. Do what you want but don't tell others it is safe to do what you do.

I agree that treatment of water is a personal choice.

My choice is mostly to assess each water source based on the topography (look at the catchment, and what it drains) and my knowledge of the use of the area (eg. don't pick up water downstream from the cave at Mobbs Swamp), and to pick an appropriate water source and drink from it without treatment.

Since I know hundreds of other bushwalkers doing the same thing, my assessment of the risk of my approach is that it is low.

It's not 100% safe, but neither is driving to the start of the walk!

I would take a different approach in other countries, but in Australia, I'm happy with my choice.

[Xplora]

I agree that treatment of water is a personal choice.

My choice is mostly to assess each water source based on the topography (look at the catchment, and what it drains) and my knowledge of the use of the area (eg. don't pick up water downstream from the cave at Mobbs Swamp), and to pick an appropriate water source and drink from it without treatment.

Since I know hundreds of other bushwalkers doing the same thing, my assessment of the risk of my approach is that it is low.

It's not 100% safe, but neither is driving to the start of the walk!

I would take a different approach in other countries, but in Australia, I'm happy with my choice.

It takes time and experience to get to the point you can safely make these decisions. For those without your experience it is much better to treat to be safe.

[GPSGuided]

There’s still a difference b/n taking an informed and calculated risk to certainty. Some can handle the risks while others can’t.