Drinking water

[dewi]

I'm getting confused (not difficult) about the whole water purification business.

As I've always understood it, to make water safe to drink you filter it, boil it, drink it... but depending on where I'm reading I keep seeing varying times for keeping the water on a rolling boil.

Without doing the science bit (primarily because I don't understand it for the most part) the nasties in the water are killed off when the water reaches 85c... boiling point is roughly 100c. So presumably the second your pot boils, the water is safe to drink?

Fully aware of the nasties (e-coli, salmonella, microsporidia etc) but taking it a further, throughout history there must have been periods where humans didn't filter or boil their water at all and just drank it. Considering the human race still exists, there has to be some water sources that at the very least are less contaminated than others, otherwise humans would have died off many thousands of years ago.

Not suggesting anyone should just be tapping ('cuse the pun) into any old water source and not purifying it before drinking, but at some point humans must have... it isn't just modern pollution that contaminates the water... if a cow is lying dead in the stream 2 miles up, all the water is being filtered through rotting flesh... so did the earlier humans just rely on pot luck?

 

[homesicksteve]

'nasties' can bind with larger particles requiring longer boil times.

At Altitude water boils at a lower temperature requiring longer boil time.

The need for clean water in history was a driving force behind the brewing industry. Mead.

 

[Goatboy]

Water purification is a big subject. Think the best single source on the subject is in the very good book "How To S*** In The Woods". Used to use it a source when teaching it to staff for years.
On water purification in the past before germs were understood for long enough the probable most common method was brewing it into beer. Not superstrong stuff but everyday small beer. Once a babe was weened it was onto small beer.
But potable water has been sought and guarded all over. Some of the superstitions and beliefs around wells and springs may come from some of them being safe water. Suppose living in Scotland I take it a little forgranted, I'll still drink from an upland burn and I happen to live where the UK most popular bottled water comes from. Though the water from my old farm well was the sweetest I've ever tasted.
There is a school of thought when travelling to drink the local water, get the runs, and you should be okay in a couple of weeks. Doesn't really work though as there are some nasties that don't go away. When they've analised poo either dug up from Viking sites at York or in European salt mines from the bronze age they've found that the guts of the depositers must've been a zoo for intestinal flora & fauna.
So I think our forebears lived with it, maybe ate the odd bit of herbage to scour out their system and maybe some in certain areas didn't have any due to water quality.

Sent via smoke-signal from a woodland in Scotland.

 

[dewi]

Steve, when you say nasties binding with larger particles, what do you mean?

I was reading a thing from an university boffin where he was saying that if you boil at between 63c and 65c it will kill most bacteria in 30 minutes, but boil at 73c -75c it will kill most bacteria in 15 seconds. Given that it takes a good few minutes to get to 100c (boiling point) by the time the water has got to 85c, the bacteria is deader than a dead thing that is dead.

When it comes to altitude, the boiling point of water reduces by what, 1c per 1000ft roughly? So unless you're above 15,000ft (halfway up Everest) then the bacteria is going to be dead when the water boils.

Already knew about the beer thingy for safe drinking water... I was thinking more about before humans even knew how to boil water... perhaps even pre-firestarting... they had to drink from somewhere. Which also brings up the question... why do animals of multiple species not have to boil water before they drink it? And I'm thinking of apes and tigers rather than whales

 

[rik_uk3]

80c will do the job up to around 4000 feet, in the UK bring to a rolling boil 100c and jobs done.

 

[John Fenna]

In pre-boiling days man probably just put up with things like the trots and developed a natural resistance to some bugs by constant exposure ... mind you , life expectancy was MUCH less, infant mortality etc was MUCH higher and pain and suffering a lot more common than it is in Modern societies....

 

[British Red]

Steve, when you say nasties binding with larger particles, what do you mean?

I was reading a thing from an university boffin where he was saying that if you boil at between 63c and 65c it will kill most bacteria in 30 minutes, but boil at 73c -75c it will kill most bacteria in 15 seconds. Given that it takes a good few minutes to get to 100c (boiling point) by the time the water has got to 85c, the bacteria is deader than a dead thing that is dead.

When it comes to altitude, the boiling point of water reduces by what, 1c per 1000ft roughly? So unless you're above 15,000ft (halfway up Everest) then the bacteria is going to be dead when the water boils.

Already knew about the beer thingy for safe drinking water... I was thinking more about before humans even knew how to boil water... perhaps even pre-firestarting... they had to drink from somewhere. Which also brings up the question... why do animals of multiple species not have to boil water before they drink it? And I'm thinking of apes and tigers rather than whales

If your water is turbid (cloudy) the particulates may have bacteria / viruses inside them. Just because the water reaches 85C doesn't mean the bacteria has as soil etc. can act as an insulator. Take a look at my post "The Science of Water" - it covers all this

 

[rorymax]

It is not infrequently that I drink water from burns, rivers, lochs and wells etc. without filtering or boiling, if it looks clean and there is a good flow of water and the surrounds seem free from pollutants then I do.

Last year in the West of Ireland I was daily drinking water from a well for a 2 week period, only for a local to tell me that the well had tested positive for e-coli the previous year, I don't think he was winding me up.

So far I have not had any problems.

Collected rainwater, I drink without hesitation.

 

[mrcharly]

Steve, when you say nasties binding with larger particles, what do you mean?

I was reading a thing from an university boffin where he was saying that if you boil at between 63c and 65c it will kill most bacteria in 30 minutes, but boil at 73c -75c it will kill most bacteria in 15 seconds. Given that it takes a good few minutes to get to 100c (boiling point) by the time the water has got to 85c, the bacteria is deader than a dead thing that is dead.

Water won't be boiling at 63C, not at sea level, not anywhere in the UK.

You don't want to kill 'most', you want to kill 'all'.

 

[homesicksteve]

Steve, when you say nasties binding with larger particles, what do you mean?

This :

If your water is turbid (cloudy) the particulates may have bacteria / viruses inside them. Just because the water reaches 85C doesn't mean the bacteria has as soil etc. can act as an insulator. Take a look at my post "The Science of Water" - it covers all this

Millbank bags can help.

 

[dewi]

Water won't be boiling at 63C, not at sea level, not anywhere in the UK.

You don't want to kill 'most', you want to kill 'all'.

Fixed that....

I was reading a thing from an university boffin where he was saying that if you HEAT, NOT BOIL at between 63c and 65c it will kill most bacteria in 30 minutes, but HEAT, NOT BOIL at 73c -75c it will kill most bacteria in 15 seconds. Given that it takes a good few minutes to get to 100c (boiling point) by the time the water has got to 85c, the bacteria is deader than a dead thing that is dead.

Although I did say that boiling point was 100c later in the sentence... just a 'pour' choice of words.


As for killing 'all' bacteria, that is never going to happen. You're getting rid of harmful bacterias through boiling, but I don't think that kills everything whether you just boil it or boil it for an hour. Can't remember the name, but I did read of a heat resistant bacteria... going to look it up.

 

[dewi]

If your water is turbid (cloudy) the particulates may have bacteria / viruses inside them. Just because the water reaches 85C doesn't mean the bacteria has as soil etc. can act as an insulator. Take a look at my post "The Science of Water" - it covers all this

Millbank bags can help.

I did say filter, boil and drink in the initial post... I meant after you've filtered, there are varying times people say to boil.

To add to my confusion, I decided to look on the Centre for Disease Control website where they recommend boiling for 1 minute unless at an altitude greater than a mile, where it becomes 3 minutes. This is to counter cryptosporidium (nasty from human and animal poo) but when you look up cryptosporidium, it is killed at 71c, so again by the time the pot comes to boil at 100c, cryptosporidium is long dead as the higher the temperature, the quicker the nasty is killed off.

The altitude thing still doesn't make sense, because yes water boils at a lower temperature, but if you're at the sort of altitude where that would really make a difference to the nasties, then surely you wouldn't be able to breath, let alone boil water??

In pre-boiling days man probably just put up with things like the trots and developed a natural resistance to some bugs by constant exposure ... mind you , life expectancy was MUCH less, infant mortality etc was MUCH higher and pain and suffering a lot more common than it is in Modern societies....

The natural resistance sounds the most likely because otherwise with all the other nasties, such as the infant mortality, starvation, even broken bones, would have resulted in a family line being broken every other day and a gene pool so shallow that we could all have evolved to have 12 fingers and boomerang feet!

I just wonder whether that natural resistance, if it existed in the first instance, has been gradually lost through the cooking of food, boiling water etc over several thousand years... whether back pre-fire that we were maybe more like other animals and able to drink from a variety of sources without getting sick??

 

[Tonyuk]

I've always went with when it reaches a rolling boil, its safe. I wouldn't bother trying to boil turbid water for a start anyway so the whole issue of it insulating bacteria etc. hasn't really came up. What i do take issue with however is this whole "must be boiled for 10 minutes" nonsense, half of it would be gone along with a good portion of your fuel.

Tonyuk

 

[British Red]

I did say filter, boil and drink in the initial post... I meant after you've filtered, there are varying times people say to boil.

Normal filtration (with a millbank bank for example) does not remove turbidity - fine particulates pass straight through a coarse filter. If using an ultra fine filter sich as reverse osmosis then boiling is pointless

 

[pysen78]

Minute particles too small to see, and still able to shield germs inside them from boiling temps more than a second, has got to be made from some extraordinary insulating materials. I'd like to see the R-value of whatever those particles are made of, and then make myself rich manufacturing ultra-minimal-superlight insulation from it.

Joking aside. IF you've got your water to a rolling boil, there shouldnt be a problem. The (American) CDC states 1m rolling boil in this link:

http://www.cdc.gov/healthywater/drinking/travel/backcountry_water_treatment.html

 

[British Red]

Minute particles too small to see, and still able to shield germs inside them from boiling temps more than a second, has got to be made from some extraordinary insulating materials. I'd like to see the R-value of whatever those particles are made of, and then make myself rich manufacturing ultra-minimal-superlight insulation from it.

Joking aside. IF you've got your water to a rolling boil, there shouldnt be a problem. The (American) CDC states 1m rolling boil in this link:

http://www.cdc.gov/healthywater/drinking/travel/backcountry_water_treatment.html

If you think a millbank bag makes cloudy turbid water clear, you have clearly never used one. The particles are far from "too small to see"!

 

[pysen78]

Sorry BR, didn't mean to comment on the millbank specifically. (You're right, I've never used one, and before coming on BCUK I would have taken it for a boot liner if I ever saw one!)

However, my comment on temperature and particles still applies. The particles pose more of a problem regarding taste and chemical pollutants. Patogens will all be killed off by boiling.

 

[rik_uk3]

http://modernsurvivalblog.com/health/how-long-to-boil-drinking-water/

 

[British Red]

Pathogens will but particulate soil and clay, animal faeces etc. have an insualtive value. This is why some authorities recommend a boil period beyond what would be necessary without that insulation. This simply is the reason why the recommendation exists. One can debate how long and how hot such a period should be - so authorities err on the cautious side since "filtered" is an imprecise term hence the size of particulate cannot be known.

 

[pysen78]

You're correct in theory, and larger particles will take longer to "saturate" with heat, but if we're talking particles and not lumps, that point is moot.
Boil time for Chinese dumplings according to one recipe I found, is 3minutes, and those even contains pork with the risk of tricines.
Surely we can go well below 3mins if we're talking "particles"?
The reason for the "big bubbles no troubles" saying is that if you work up a rolling boil, all of the water will have been above 60-70deg C, for long enough to kill of most if not all of the nasties.
Anyways, not meaning to pick a fight. In the end, I guess best practice is to do what feels right in this kind of situation, since worrying about the possibilty of an upset stomach is about as fun as actually having one!