Brown bag effectiveness

[theScepticalPrepper]

Between the recent hacks taking 2 water treatment plants offline in the US and the UK (finally) launching the Be Ready campaign over here, I've been looking at water purification options. Should the taps run dry for any length of time, people will panic buy bottled water and you can bet there won't be enough bowsers to go around.

Obviously rainwater needs to be filtered and brown bags look to be a good first step for separating out suspended sediment but I'm having difficulty finding any specifics on their effectiveness. The sites that sell them just say they're made to the same MOD spec as the old Millbank ones but don't say what that is.

[Adjee]

No idea of any specifications on Millbank bags but we use them as a pre-filter when "out and about" and the water source is not too clean. They remove a lot of debris from your collected water but the resulting clean/clearer water still needs filtering/purifying. The advantage we find using them is your water filter does not clog up so quickly and the cleaner water passes through the filter faster. For the space they take up either in a cupboard or in your bag they are a worthwhile addition to your resources/equipment.

If you do opt for one, remember to break it in properly or the filtration through the bag will be painfully slow or none at all.

[theScepticalPrepper]

Sorry I didn't say explicitly in the first post, but I'd also be looking to use them as a pre-filter before boiling the water. Just interested to see how they compare to e.g. cheese cloth.

[ForgeCorvus]

The Millbank bag is just a canvas sock that holds about 6 pints (from memory), you fill it and let the first third run away to rinse the outside off. I think they're a 10 oz or 12 oz canvas...... Anyway, as Adjee says they're just a pre-filter.

Any fairly tight weave cotton or linen cloth will work, saying the brown bags are "Millbank spec" doesn't mean all that much.

Having just seen your follow up post.
Cheese cloth is far too open a weave for this job, you need something more like proper old bedsheets or chambray weigh shirt fabric.
I use offcuts of linen from my re-enactment shirts as filter cloths in a funnel when racking-off my "potions"