Let's imagine I'm hiking and I find a water source - like a lake, a stream or a well, and I want to fill my water bottle with it.

I have a bottle and a water filter. And a bandana. Since I can't tell if the water I see is safe, I want to filter it prior to drinking. But - how should I proceed? I see 3 options here:

  • Filter the water right away, when filling the bottle. This way I'm sure the water inside the bottle is safe for drinking.
  • Or fill the bottle with (possibly contaminated) water and filter it before drinking. This allows me to have my filter last a bit longer (as some water from my bottle could be used for purposes that don't require a clean water...)
  • Or, maybe, have a bottle with the filter in the drinking cap (or drinking straw), so if I want the clean water - I can sip it from there and if I need "just" water, I can pour it from the bottle directly (note: I got no idea if there are any good bottles with good filters/drinking straws like that).

Before filling my bottle I can pre-filter the whole water via bandana, of course, to get rid of floating particles and maybe let the UV from the Sun do some job on killing bacteria.

What would be your approach? Assuming the filter won't last forever.

  • 2
    A bandanna may filter some bulk crud, but does little to get rid of the stuff that is really dangerous. Bacteria and virus are too small for a bandanna to catch. It might catch some parasites, but I wouldn't count on it. Dec 3, 2013 at 21:15
  • That's why I treat 'cotton-filtering' as a pre-job that I like to do on all water. Doesn't hurt and doesn't waste much time and is useful. Kind of:)
    – kender
    Dec 4, 2013 at 8:44

3 Answers 3


Filter the water right away, when filling the bottle. This way I'm sure the water inside the bottle is safe for drinking.


Why? The main point for me is accessibility of that water. If you come to a situation where you need fresh water, then it may not just be because you've set up camp, you've got a while to spare and you feel like a drink. It may be (for example) that you've cut yourself and need to wash the wound, and in that case you won't have time to sit there with a filter and sort it out - so chances are you'd just use the water as is or go without, neither of which are ideal scenarios.

Practical reasons are also worth pointing out - dealing with dirty and fresh water in separate bottles has the potential for getting them mixed, especially if you're tired after a long day of hiking, that could go rather wrong. These chances are compounded if you're hiking with someone else who may not know what water you've put in what bottle.

Personally I wouldn't be worried about a bit of filter life here and there, I'd much prefer to have a stable, fresh supply of water I don't need to worry about.

Also worth mentioning as your third option - good filters are really rather slow, so I'd be incredibly wary of using any filter that was in the straw directly. If the filter was any good then you simply wouldn't get enough to drink that way!


I use a Sawyer Squeeze filter and its pretty quick, light, and easy. You fill up a pouch that looks like a big Capri Sun and then just squeeze it out through the filter into your bottle or bladder. It comes with both a filter cap and a regular bottle cap, so if you were in a hurry you could fill the pouch at the water source, cap it, and filter it later. (I think the filter will also screw onto a water bottle)


  • Can this filter be used as gravity-fed filter, or you do have to squeeze it? :)
    – kender
    Feb 26, 2014 at 11:46
  • I have never used the filter with a gravity set up. It doesn't come with tubing or anything in the box. I have seen where people modified it and used it as such, but I am not sure how.
    – MalPal
    Feb 26, 2014 at 18:38

I have never used it and it looks bulky and rather expensive, but the LIFESAVER® bottle makes your third option otherwise practical. You fill the bottle from one end and get clean water from the other; it is capable of filtering biological threads directly so there is no wait period. Reviews I've seen are a bit mixed, but it does seem like a unique offering at this time. Here is a video presentation from the proprietor:


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