I was recently walking in the North Pennines on a hot day. 10 miles into a 16 mile walk, I stopped to check my 2.5l water bladder and saw that it was almost empty. This naturally caused me some anxiety.

Much of my day was spent walking across blanket peatland bog so there was an abundance of water underfoot but I wasn't sure how safe it would be to drink. Would it be safe to drink using a Sawyer filtration system?

Prompted by the replies, I should add that I recently overheard a conversation from a local conservationist in the Pennines that there were trace amounts of arsenic in a stream near some abandoned mines. Subsequently sharing the following links for awareness:

3 Answers 3


EDITED TO ADD: Please also read the other answer by cbeleites unhappy with SX about the risk of heavy metal contamination. The information in my original answer (below) is still accurate regarding microbes, but you also need to worry about heavy metals, and a water filter will not remove those. Apparently the low pH of bog water makes the risk much higher than I realized. That makes the historical mining practices of the area extremely important to your decision about whether and how much of the water to drink.


Yes, a Sawyer water filter (or any other reputable brand of water filter) will remove microbial contaminants and make water safe to drink. The exception is if the water is chemically contaminated, eg by a nuclear plant, factory or mining. There is some history of mining in the North Pennines, so it would behoove you to look up where the abandoned mines are in advance, and try not to drink water from nearby. But as a general rule of thumb, if the nearby vegetation looks healthy, it should be find to drink filtered water from that site as a one-off. If you frequently hike the same route and regularly drink the water, then you might worry about longer-term health effects, and should do some more research about the historical land use along that route and possible chemical contaminants.

The issue with peatland water is that it tends to have lots of suspended vegetative particles that will quickly clog a filter. (This is based on my experience with the water in Dolly Sods, a peatland wilderness area in West Virginia, USA.) As the filter gets clogged, it will take more time and effort to push water through it. And Sawyer water filters are quite slow to begin with. Make sure you bring the cleaning syringe with you. You may need to flush the filter several times during the process of refilling a 2.5L water bladder. (And remember to only use already filtered water for flushing.)

I have found with the Sawyer water filters that the pouches are extremely difficult to fill from anything other than a water tap. If you try to fill the pouch by pushing it under water, the water pressure compresses it, so there's no empty space to fill with water. When you pull it out of the water, you have only half a cup or so in the pouch. It's much faster if you bring a spare water bottle, fill the bottle from your water source, and pour from the bottle into the pouch. Or if you have a bottle that the filter fits onto, you can attach the filter to the bottle and drink directly from it, using the filter like a straw. But then you'll have no way to flush the filter if it gets clogged, since you won't have any clean water. So it's probably best to test that method while you still have water left in your drinking bladder, to find out how much peatland water you can drink through a filter before it gets clogged.


Peatland/bog water has lots of humic acids. They lower pH (see also @SherwoodBotsford's answer), and they are chelating agents.

Both low pH and chelating mean that they tend to mobilize heavy metal ions, As-species behave in a very complex manner (see e.g https://www.publish.csiro.au/EN/EN05025 for a start).

I'd therefore avoid drinking bog/peat water in regions where metal mining is done or has been done in the past (mining here is a surrogate marker for those metals being around - even where no mine has been, my guesstimate would be that it may be more than I'd like to drink even though it's likely less heavy metal would be around than in active or former mining and downstream thereof).

E.g. I know some areas (including bogland) in the Ore Mountains where e.g. people are asked not to eat vegetables from their gardens since the soil contains heavy metals (and arsenic). Water coming from the bog is used for drinking water, but of course that undergoes chemical (and microbiological) analysis on a regular basis*.

OTOH, I read that the Northern Pennines are limestone, i.e. highly permeable for water. Any water you collect on the surface near the top of a hill (as opposed to springs and rivers at the bottom of a valley) is thus mostly rainwater and unlikely to be contaminated by heavy metals.

In contrast, I'd be much less concerned in this direction with peats/bogs e.g. on the Canadian shield as long as we're not talking of somewhere closely downstream from mining effluents): the ones I've seen are on pockets of extremely old bedrock which water doesn't permeate. The water is basically surface (rain) water rather than sources of ground water that has been going through large amounts of soil and rock and may have dissolved heavy metals from there. This means that basically this water is in contact with comparably small amounts of rock, and there has been sufficient time for the heavy metals to leech out (or other stuff: that's also why it is so low in nutrients like N and P). (Note that this is not in contradiction with mining: mining can expose rock that has not been in contact with the surface water)

All this being said,

  • it's of course better to drink such water than to die of dehydation, there's a large difference between being exposed once to water with a possible contamination and using it as drinking water on an everyday basis (or planning to use it on extended tours).

  • We humans don't need that much water for other purposes than sweating. Using the peatland/bog water for cooling yourself, e.g. by soaking your shirt and cap etc. can significantly reduce your need for drinking water, and you can safely use water that you'd rather not drink.

  • Bottles give a rather direct feedback on how much is still left. It may be worth while switching to bottles or to a reserve bottle in addition to the bladder: the earlier you realize that you need more water than planned, the earlier you can start saving drinking water by switching to the wet shirt approach.

*The place I'm thinking of is at an old road with the illustrative name of Giftmehlweg, literally translated poison meal way, Giftmehl is As(III)oxide powder obtained from the smoke of ore roasting - a practice followed for centuries before exhaust gas treatment was invented. In areas where ore was roasted, arsenic contamination will be widespread because it was distributed via the smoke of the roasting ore.

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    Thank you for this very important information. I will definitely keep it in mind when choosing where to collect drinking water in the future. I added a note to the top of my answer encouraging people to read and consider your answer as well.
    – csk
    Commented Jun 15, 2021 at 16:25
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    In response to comment on my answer: Once mining is involved, you need to proceed with caution. Because granite is essentially impermeable, toxins can move large distances. See the story of the Dryden paper mill and mercury poisoning of the English river. Mind you, the toxic part was eating top predator fish, not drinking the water. Beaverlodge and Nero Lake near Uranium City are still virtually sterile, not due to heavy metal, but due to the acid used to extract it. The lakes are nearly landlocked with very little flow. I took a sample to the lab. No radioactivity. Commented Jun 16, 2021 at 14:39

You have to make a judgement call based on what you know about activities in the area. Peat bogs tend to be both very low in nutrients (life is hard if you are a small organism in water) and very low in pH (few bacteria thrive at pH of ~4)

In Canada, I have drunk water untreated from:

  • North Saskatchewan

  • Red Deer

  • South Saskatchewan

  • Red River

  • Winnipeg River

  • English River

  • Fraser River

  • Nechako River

  • Churchill River

  • Slave River

  • Athabasca River

  • Lake Superior

  • Lake of the Woods

  • Reindeer Lake

  • Wollaston Lake

  • Blake Lake

  • Lake Athabasca

  • Great Slave Lake.

  • Every creek I crossed in Rocky Clearwater Recreational Area.

  • Every creek I crossed in Willmore Wilderness.

I'll admit that the Red, Red Deer, and Nechako were a bit dodgy, and I was lucky. The Slave and the Athabasca contained so much silt/sand you'd let it settle for 10 minutes then drink only the top half.

In 30+ years of 3-5 weeks in the bush per year, I've yet to be seriously sick, although there have been single days where I used a week's worth of toilet paper.

  • I see a substantial difference between pockets of bog on very old bedrock and mining areas with limestone which is easily penetrated by water. Would you mind looking over my answer whether you agree on the Canadian shield part? Commented Jun 13, 2021 at 15:15

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