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LifeStraw has a 0.2 micron filter. Since "most bacteria are 0.2 µm in diameter and 2-8 µm in length" (source), is it safe to drink water from any source using LifeStraw without boiling? (India in particular) Or should I better use water purification tablets?

enter image description here

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    Bacteria aren't the only concern in contaminated water; viruses and chemical pollutants could be much smaller. I don't know how much of an issue these are in India, though. It might depend on what specific part of India you are talking about. But this product certainly can't guarantee you safe water from "any source". – Nate Eldredge Sep 18 '16 at 21:09
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    A LifeStraw should be a hail mary for emergency use only, using bottled water from reliable sources is preferable – user13044 Sep 19 '16 at 1:19
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    @Fiksdal How do you know? – A E Sep 19 '16 at 19:02
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    @AE I may be working for LifeStraw... – Revetahw says Reinstate Monica Sep 19 '16 at 19:37
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    Just drink bottled water, coke, and fanta like everyone else :) – Navin Sep 20 '16 at 8:40
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No.

Physical filters using pores with 0.2 µm (microfiltration) cannot

  • remove heavy metal contamination (lead, mercury). This is possible with ion exchangers, distillation and nanofilters (see below).
  • remove viruses. Most of them are too small and will easily pass through the filter.
  • remove substances like salt and magnesium which make the water undrinkable. It is possible with the same principle and is then called reverse osmosis, but it needs filter sizes about 1 nm. Also possible is the use of ion exchangers.
  • remove pollution with big particles. For that reason the filter does not work alone, but needs prefilters like charcoal which prepares the water for the microfiltration. Such units used by survivalists and the military have several components to make water drinkable.

This does not mean that the product is not working or is unsafe, it simply means that you cannot trust any source. Boiling is not able to remove heavy metals (in contrast, it increases the concentration) and some pathogens, but for the "normal" usage it is sufficient. Inform yourself about the problems you may face in your destination country (In India it is mainly giardiasis).

The normal and quite cheap way in India and in other countries for getting water is always use packaged, unopened(!) bottled water. I for myself prefer Micropur (silver ions) for water preparation.

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    Looks like LifeStraw is effective against giardiasis (too big to pass through the filter). – Sparkler Sep 19 '16 at 2:27
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To add to Thorsten's excellent and quite accurate answer:

No, it takes quite a lot more than that to create perfectly safe water. For example, here's my Indian water purification system. I know it's not feasible for travellers, but I'm including it to illustrate just how much is actually needed to get really pure water: enter image description here

Some things to note about it:

  • It needs electricity to pump water through a very fine membrane (and another, rougher one). This process is known as reverse osmosis. It's the same technology that's used to create the vast majority of bottled water in India. It needs an electric pump because the holes in the membrane are so tiny that even viruses can't get through. This makes pumping harder, and also means that there's a significant amount of wastewater that doesn't make it through the membrane, but goes back out into the ground instead.
  • It has an additional ultra-violet filter which kills any number of microorganisms that might have made it through the membrane somehow. This is for absolute redundancy.
  • It removes all dangerous chemicals, metals, minerals, salts, etc. from the water as well. This is needed where I live, since there are plenty of unhealthy substances in the ground water. The water that goes in shows roughly 600 parts per million of dissolved solids. (I measure it myself with a meter.) The output has around 20. (My machine also adds some healthy minerals to the water.)
  • I paid 13.000 INR for that machine, while the LifeStraw sells for 1100 INR on Indian Amazon.

Needless to say, much of this can not be accomplished by the LifeStraw.

Many parts of India have severe problems with industrial waste draining into the ground water. In the area where I live, there's no sewage or drainage system. Much of the household sewage and wastewater (as well as industrial and agricultural waste) goes directly into the ground. That includes detergents, chemicals, pesticides, feaces, etc. from factories, farms and households.

In some areas, water comes from lakes and rivers, and these are often polluted and contaminated as well.

I use RO water for cooking too. So does any halfway decent restaurant. Such restaurants and households have their own RO machines.

Use bottled water.

For short trips I certainly recommend bottled water.

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    Do you need to add any minerals to the pure water it produces to make it healthy for long-term consumption? I know that this is done in places where the city water supply goes through reverse osmosis (typically when the only water source is the sea). – Szabolcs Sep 19 '16 at 9:21
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    @Szabolcs Natural, healthy water (like that from clean rivers, etc.) contains a certain amount of healthy minerals. The World Health Organization has stated that it may be less than healthy to consume totally distilled water (like RO water, which is totally cleared of practically everything.) This is because it lacks natural, beneficial minerals. Therefore, the largest bottled water manufacturers in India add some healthy minerals to the water. So does my machine. – Revetahw says Reinstate Monica Sep 19 '16 at 9:25
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    @Szabolcs Please note that for short periods (like on holidays, etc.), even demineralized water is probably nothing to be worried about, as our bodies keep internal reservoirs of minerals and can probably do fine for a few weeks. – Revetahw says Reinstate Monica Sep 19 '16 at 10:28
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    In fact, drinking distilled water while on a healthy diet is not dangerous as we get the required minerals from other sources. You could also drink distilled water while taking additional supplements with it. – Vilmar Sep 19 '16 at 14:06
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    @Vilmar Unfortunately, it might not be that simple. The WHO paper I referred to earlier has quite a long chapter on potential risks. Not all of them can be mitigated by taking pills or having a varied diet. It's too technical to get into here, and I'll readily admit that I don't fully understand the subject matter. But it's a much researched subject. I'm sure you could find some references for you statement as well. – Revetahw says Reinstate Monica Sep 19 '16 at 14:16
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Thorsten has an excellent response re: the filtration failings of the lifestraw itself.

I would find sucking on the lifestraw for all drinking water tiring. When I visited rural China, I used a tiny, battery-operated UV based sterilization system. It would sterilize 500ml of water at a time, plenty for everyday use. I also used the water to wash my own utensils as I didn't always trust the utensils provided at rural restaurants. I even "nuked" the bottled water when I didn't trust that the bottle hadn't been refilled.

One thing to consider, for example: how are you going to rinse your mouth after you brush your teeth if you only had a lifestraw. Many tourists have unthinkingly used faucet water by mistake!

There's also the problem that water is not the only source of contamination. You need to be very careful about the type of food you eat and how it was prepared, stored, and served to you.


Note that UV and chlorine/iodine systems don't remove chemical contaminants. Many people use an activated carbon filter in conjunction. Still, a carbon filter and UV sterilizer can fit in a large nalgene water bottle and operate on batteries without ac power, which is more can be said for reverse osmosis systems.

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    Local people may develop immunity to bacteria or viruses, but not to chemical contaminants. If the source of your water is the same the local people uses and they are not dropping dead like fleas, you should not worry about chemical contaminants unless you are going to stay in the area for a very long time. – SJuan76 Sep 19 '16 at 0:27
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    Even trace amounts of many toxins such as lead, PFOAs, and mercury will bioaccumulate. I'd rather not risk my long term health. Thanks. – RoboKaren Sep 19 '16 at 4:04
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    @SJuan76 Just because people aren't "dropping dead like fleas" doesn't mean they aren't ingesting harmful substances from the water. Saying that you "shouldn't worry" is irresponsible, IMO. Why would you risk drinking water that may contain harmful contaminants when bottled water is cheap and readily available? "Ah, just a bit of mercury won't hurt."? No, thanks, I prefer zero over a little bit. – Revetahw says Reinstate Monica Sep 19 '16 at 6:52
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    @SJuan76 I'm not talking about "trace" chemicals. Many parts of India have severe problem with industrial waste into the ground water. Where I live, there's no sewage or drainage system. All the household (and industrial) waste-water just goes straight into the ground. That includes all the detergents, chemicals, etc. from all businesses and households. And yes, I used RO water for cooking as well. So does any halfway decent restaurant. Restaurants and households have their own RO machines. – Revetahw says Reinstate Monica Sep 19 '16 at 7:36
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    @SJuan76: and what if the locals are dropping dead like flies? Life expectancy in India is 13 years less than in the country I live. Obviously that's not solely or even mainly due to chemical contaminants in water, but it is partly due to that. So am I going to perform a sophisticated epidemiological study of each region I visit, or am I going to prefer RO water, just like the locals who can afford it do? I suppose if they're worried about the water they shouldn't live there either? ;-) – Steve Jessop Sep 19 '16 at 11:15

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