The Ultimate Guide to Millbank Bags

by Elvis Jai Closs on January 10, 2022
The ultimate guide to Millbank water filtration bags

Every outdoors person knows the importance of hydration - your body will start to shut down after 3 days with no water.
For weekend camping trips or longer expeditions, the correct gear for collecting, carrying, and purifying water is essential.
Originally invented by the British Army, learn why Millbank these bags are an essential piece of kit and the best way to use them.

What is a Millbank bag?

A Millbank Bag is a water filtration device, designed to filter out all of the detritus from the water. These detritus include sand, mud, silt, or other suspended particulate matter.

Why are Millbank bags important?

Removing all of the detritus before further sanitation is extremely important. Even if there are no waterborne diseases present, turbid water will irritate and cause damage to your digestive system. In addition, turbidity can reduce the effectiveness and lifespan off other water sanitation systems including the Life Straw, for example.

What are the limitations of Millbank bags?

However, a Millbank bag will not filter out pathogenic organisms, unless those organisms are attached to the detritus that is filtered. This is why additional forms of sanitation are required, including chemical or heat sterilisation. If your water source is already clear and has no detritus present then there is little advantage to using the Millbank bag. Although, few of us are lucky to find such water sources out in the wilderness!

So, how do you use a Millbank bag?

Using the Millbank bag is pretty self-explanatory, but there are a few essential steps and useful tips and tricks to know!

1) Start by thoroughly soaking and massaging the bag underwater. This process will help saturate and loosen the bag's fibers, so the water drains through faster. Otherwise, it can take hours for the water to filter through the bag.

3) Then, after the water level meets the transition line start to collect the water that is draining through. Filtering a 1L bottle in our Millbank bag will take around 20mins, although sometimes it is a little faster. If sanitising over the fire, it's useful to collect the water straight into a metal pan or cup.

4) After the bag is empty, wash off the bag, fold it up and tuck it neatly away in its waterproof carrying bag. The bag will need cleaning from time to time. This is because the build-up of detritus can cause the filtration process to slow as it blocks the passage of water through the bag.

5) Make sure to sterilise! Remember, the Millbank bag is designed to aid further sterilisation, not to purify water completely. MCQ Bushcraft has a great video how to sterilise water which is available here.

Forest Fundamentalas Millbank Bags

At Forest Fundamentals, we have been long-term users of the old British Forces Millbank bags but pleae be careful doing this! Today, mostly all Millbank bags being sold are surplus - they have seen years of use, and were most likely used to filter oil and other nasty chemicals. So we thought, why not start designing and handmaking our own!

Our Millbank is a handmad copy of the original Birtish Army Millbank Bag. All of the dimensions are the same. However, after some testing, we decided to go with a slightly thicker and desner 12oz canvas for better filtering capability.

However, after some testing, we decided to go with a slightly thicker and denser 12oz canvas for better filtering capability. Unbleached canvas is not flawless but is natural and safer for us and the environment. You can checkout the full list of design changes and our Millbank Bags here.