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I'm in Colombia, and recently visited lake Neusa - highly recommended, by the way!

The advice on drinking tap water in Colombia seems to be generally, big city/tourist hub = fine, otherwise avoid.

Despite this advice, I've still mostly avoided tap water in the cities, apart from brushing teeth. This is mostly due to an instinct of city = pollution = bad rather than anything evidence-based.

However, I noticed whilst up at lake Neusa that my instinct told me the opposite, that the water would be fine to drink. Being up in the mountains, next to a beautiful lake, it gives you a very strong intuition that everything's going to be clean, fresh, and OK. After all, images of mountain vistas are used heavily in marketing for bottled water, so it can't be just me!

Is there any basis in fact for this intuition? Are there any reasons, or evidence, that water up in the mountains is likely to be in any way safer and cleaner than that in towns and cities, given broadly similar water purification standards and technologies?

Off the top of my head I'm thinking it could simply be easier to clean in the first place due to being fresher and more quickly replenished, less exposed to pollution of various kinds, etc.

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    No, your intuition is not correct. One of the main concerns with drinking water is bacterial contamination and if there is livestock in the area, it's a very real possibility also in the mountains. Also, 'old' water is also safer, water from quickly replenished sources like karst springs could have been exposed to contamination very recently. – Relaxed May 25 '15 at 3:52
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    Note that tap water isn’t necessarily from the immediate surroundings of the tap. It may have been transported over hundreds of kilometres. – chirlu May 25 '15 at 3:55
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    This is probably one of the most important questions yet asked on Travel.SE. Thank you. – dotancohen May 25 '15 at 9:34
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    As others have said - a VERY dangerous assumption. Contamination is liable to be the rule without specific action to avoid or remove it. Doing your =own Chlorination is very easy and effective if you wish to. – Russell McMahon May 25 '15 at 9:59
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    This whole issue is counter-intuitive and pretty much impossible to rule without testing water samples. Eg river downstream might be cleaner than upstream. This sounds impossible until you realize that if river is contaminated close to the source and other, cleaner streams mix in later, it dilutes the contamination and brings it to safer levels. – Agent_L May 25 '15 at 20:31
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My parents live in the countryside (in the UK, not Colombia, admittedly), their tap water comes from a natural spring. They don't drink it.

The problem is the water like this tends to be in the open have a lot of crap can get in there. Including literal crap, live and dead animals, chemicals from farms and other businesses, etc, etc. The closer you get to the water source the cleaner it's likely to be, but there's also a chance that the groundwater itself is already polluted. Higher water sources may be safer, but probably not safe.

In the nearby towns the water comes from (essentially) the same source, but there it's filtered and must meet strict standards.

Obviously this varies per country but in general tap water is pretty safe in most western countries. You're in Colombia which does have standards (PDF, Google translation). I've no idea how well enforced they are and the general advice on-line is to drink bottled water.

In short, there's no guarantee that mountain water is safer than city water. If both are treated they should be equally safe -- although it's likely that there's less testing and enforcement for treatment in more rural areas. Also city water may be more aggressively treated, which may affect the taste -- which is actually the primary reason a lot of people don't drink city water.

Finally, as pointed out in the comments, city water is just as likely to come from a source in the mountains so the starting point could be the same.

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    On-line advice usually is to drink bottled water pretty much everywhere except home city/country of the person giving the advice. – Agent_L May 25 '15 at 20:01
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This probably won't apply to Europe, but I live next to this awesome lake, and a friend of mine actually own a water bottling company!

Kandy lake

Above is the Kandy lake, which is located right next to a few mountains. We don't even touch this water.

However, I still think it's somewhat safe to assume that you can drink water that is right next to a mountain.

Adams peak

The above image is of Seetha Gangula, which translates to English as the river of cold water. You can drink this water!

The difference between what you can drink and what you can't is based on the source of the water. Water from rivers are a big no no, but with a significant effort, you can find springs, which provide the best tasting water you'll ever find! It's never pure H20 (which tastes terrible by the way), but loads of minerals mixed to it.

There are two types of natural water bottling types: Spring water and Mineral water.

Spring water must be collected at the source (spring), and after a quite a few purification, you can safely drink that water. But the truth is, this purification process hardly makes a difference. Spring water, if collected in a hygiene way, is good to drink right away.

My friend owns a bottling company that produce mineral water. This usually refers to water taken from a river, and after heavy purification.

Government health departments usually require both of types to be purified first.

As for lakes (my first photo above), people put all the garbage there (animals will become garbage at least), and since the water isn't flowing, it is not safe to drink them at all.

  • Pure H2O tastes horrible? Honestly, try tasting it once, it just tastes as boring as any other water ;-) It's better than a lot of tap water, but definitely not as good as some water. But beyond that, good answer and +1 . – David Mulder May 26 '15 at 1:18
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    It's possible he's referring to distilled water which while I don't consider "terrible", still doesn't taste very good. I've consumed more than my fair share from onboard distilleries while in the US Navy or on Merchant Marine ships. Both treated the water with some form of either chlorine (bad taste) or bromine (not so bad), but neither tasted good, even right out of the distillers. I live in Washington State in the US now, and the water coming out of the taps here is fabulous, I have no idea why anyone buys bottled water around here. – delliottg May 28 '15 at 22:25
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The advice that water in cities is more likely to be drinkable is based on that larger urban water systems tend to have some degree of water treatment (i.e., chlorination, ozone, or UV-based) that will kill bacteria, viruses, parasites, and spores. However, the water source itself may be of questionable quality from the perspective of other pollutants (heavy metals, pesticides etc.).

Rural tap water may not have any sort of water treatment and be pumped straight from the lake or aquifer. The water could easily be a source of giardia or other parasites. That said, lakes in high mountain regions are likely to be free of industrial pollutants like mercury, pesticides, and fertilizers.

tl;dr:
City water == may be polluted with industrial chemicals but may be treated and relatively free of infectious pathogens.
High mountain water == clean of chemicals but may have infectious pathogens.
Low rural areas == may have both agricultural runoff as well as pathogens

Solution: In cities and low rural areas, buy bottled water. In mountain areas, bring your own UV or chlorine/ozone tablets and treat the tap water anyway.

I have a UV SteriPen which I use hiking or in countries with iffy water treatment systems. Note that this advice applies to places where tap water is considered suspect -- notably, mainland Asia, SE Asia, S. Asia, parts of sub-saharan Africa, rural Latin America, etc.

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    Why would pesticides be more likely to be found in urban water systems? Is it even a concern anywhere for occasional consumption? I think bacterial contamination is the main concern in both cases with livestock a special problem in the countryside and human contamination a bigger issue in cities. – Relaxed May 25 '15 at 3:55
  • I did specify as a given at least broadly similar standards of treatment, i.e. at least rudimentary processing. Obviously I realise that drinking water straight from the lake will probably end badly :-) – techpacker May 25 '15 at 4:02
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    Cities tend to be located near rivers and use river water. River water tends to come from runoffs from higher tributaries. Runoff from agricultural fields tends to be high in pesticide and fertilizer contamination. – RoboKaren May 25 '15 at 4:35
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    You should have added a location/region for your guidelines, I think. In western Europe all tap water in cities is safe to drink, in most countries in Europe all tap water is safe to drink even when the locals do not always trust it. In tests it has come out as cleaner and more safe than bottled water, usual in the Netherlands. – Willeke May 25 '15 at 7:33
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    This answer is completely wrong. There is no reason for city water to be polluted with "industrial chemicals". There is no reason for rural water to be clean of "chemicals", as pretty much every well has problems with agricultural runoff this days. I guess pesticides count a "chemicals" in your book. Bottled water is either regular city tap water or comes from rural sources anyway. The real issue is: whom do you trust more - water system health inspector or bottled water manufacturer. This cannot be decided without knowing laws of the country and how are they upheld. – Agent_L May 25 '15 at 20:06
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Here in Colorado just about all the rivers, even little creeks, have giardia spores in them. Giardia is really a tough thing to kill. Just boiling the water won't do it. There are some very tiny filters that can, but you have to be very gentle with them or the filter breaks.

The DEA has halted sales of iodine, which could purify water, because iodine can be used in meth labs.

I want to guarentee you that you'll have a really rough time if you get giardia. It's like the worst GI problem you've ever had X a million. Go far out of your way to avoid it.

City water tends to be chlorinated and goes through things like sand that effectively strip stuff like giardia out. While we have a cabin in the mountains, we bring up 5-10 gallons of water when we go there, even though there's a creek 50 feet away from the cabin.

thanks, Dave Small

  • Essentially all the statements in this answer are false. Here in Colorado just about all the rivers, even little creeks, have giardia spores in them. Citation needed. I'm more familiar with detailed scientific studies of the Sierra, but basically water sources in backcountry mountain areas in the US don't have enough giardia spores to cause disease. You need to drink about 20-30 spores (on the average) to contract giardiasis, and in locations that have been studied in the Sierra, this would require drinking hundreds of liters of water. – Ben Crowell Aug 9 '16 at 20:25
  • Giardia is really a tough thing to kill. Just boiling the water won't do it. False. Protozoa cysts are killed rapidly at about 55 C, so you don't even need to bring the water to a boil. The DEA has halted sales of iodine, which could purify water, because iodine can be used in meth labs. False. You can buy halogen tablets at REI. I want to guarentee you that you'll have a really rough time if you get giardia. It's like the worst GI problem you've ever had X a million. False. Giardiasis is most often asymptomatic. About a third of toddlers and 3-7% of adults in the US have giardia. – Ben Crowell Aug 9 '16 at 20:29

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