To find the best filter in the world you have to look for the worst water, and the greatest need for truly clean water. That you'll find in South America and Africa, where you will also find the Just Water filter. It is silver impregnated, so it will not grow algae, and the middle is filled with activated charcoal.
Made in the USA, the Just Water filter removes all particulate down to .2 microns, or 200 nanometers. This covers:
99% Arsenic 5
99% Hydrogen Sulfide (Rotten egg odor - H2S)
95% Chlorine and Chloramines
99% bad taste
99% bad odors
90% Rat poisons
95% Polyaromatic hydrocarbons
100% Giardia Lamblia
100% live Cryptosporidium (WRc Standard)
100% Cryptosporidium (NSF standard 53)
100% E. Coli, Vibrio Cholarae
99.999% Salmonella Typhil, Shigella Dysenteria
This filter will also greatly reduce fluoride, and the only filter that will remove more harmful additives than the Just Water filter is a Reverse Osmosis system. The problem with RO is that it wastes 90% of the water that is fed into it, and requires constant pressure on the water. In an offgrid survival situation, there is no better filter than Just Water.
This is a low profile gravity filter, which when new will give you about 1 gallon per hour.
The Just Water filter comes with a microfiber sock, to filter out heavy particulate first, preserving the life of your filter between servicing.
To clean your filter, once it turns brownish, scrub off the outside layer with a brush or green scrubbie, but don't get too aggressive because this will reduce the life of your filter. It takes a good year under daily use conditions with moderately clean water to require enough scrubbing to remove the outer layer entirely.
Inside this filter is activated charcoal, which will last the life of the filter to get rid of chlorine and other soluble chemicals.
You mount this filter dome up in the bottom of a bucket or pot, drilling a hole in the bottom for the spout to stick down. This is then put on top of a second bucket or pot that has a hole cut in it's lid to also allow for the spout. The water fills the bottom bucket, which will be clean and good to drink.
Every filter comes with a spout for your bottom bucket.
It is common to use two filters in one bucket bottom to retain a good enough flow rate as the filter gets dirtier and slows down some.