Millbank Bag – Any Experience?

[Zachary]

On a recent late summer overnight at Mount Saint Helens, I set camp up at/above tree-line and was able to find water from the melting glacier/ice field near the rim. The challenge is that because there had been no significant precipitation in over six weeks, when the water reach our access point, it was so filled with ash sediment that I knew was going to clog my filter on the first pass. I pre-filtered the water through a bandana (twice), but the filter still became clogged. We used some of our clean water to backflush, but that was not enough.

Once I came back to civilization, I began researching this problem and discovered millbank bags. They seem very effective to use as a pre-filter before filtering through a Sawyer/Katadyn/etc. (with purification afterwards, if necessary). My question is this: Do you have any experience using a millbank bag and if so, do you believe that it would be effective at filtering out most of the ash/sediment from a volcano water source?

[Dan]

I don’t have experience with that particular filter, and I apologize in advance that my response is not directly relevant. However, I have on a few occasions been forced to drink from water sources with a ton of sediment, including mud puddles, and maybe my experiences will be helpful to someone. I don’t think I found an ideal solution, but I always got through it, and it never ruined my trip or clogged my filter past the point of no return.

One thing that helped was hanging the water in a bag overnight, allowing the sediment to … sediment … and then carefully draining out the very bottom part. In the lab, one would use a centrifuge to separate particles from supernatant, but gravity was the best I could do in the field. Still, it helped a LOT, and I was able to filter it afterwards. You need to be careful to keep the bag inverted and very still, or the entire effort will be in vain. For me, it worked best to hang the bag with the opening at the bottom and a piece of tubing attached, crimped and clamped. That way, I was able to drain the bottom of the bag just by removing the clamp from the tubing. Even unscrewing a cap on an inverted bag can generate a fair amount of mixing.

Complementing the above approach, I purified some silty water chemically, and just dealt with it. I always have iodine or chlorine tabs as backup. It didn’t taste great, but it was still water. I don’t carry a steripen, but I imagine that would work just as well.

[Zachary]

Thanks Dan. I’ve done this as well in previous trips where time allowed the sediment to settle. It is a good technique if time allows.

[Russell M]

I’m really surprised this hasn’t gotten more comments from such gear heads around this forum. The Brown Filter Bag which is a modern authentic replica of the famous Milbank bags used by the British Army does just as good at pre-filtering sediment as Alum does and it doesn’t require adding heavy metals to your water. It also can be used over and over again, is light, and is very durable.

https://paulkirtley.co.uk/2017/rupert-brown-water-filtration/

[Terran Terran]

Filter bag

[Author]

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