Getting the right water filter or purifier for you can be a tricky business as it's not always easy to compare like for like, hopefully this guide should get the right product for you.
The first thing is the difference between a filter and a purifier.
A water filter mechanically removes any particle in the water down to a certain size (depending on the filter element). For most filters and ALL the filters Facewest sell this is at least 0.2 microns which will remove bacteria, protozoa, giardia and cryptosporidium. Some water filters also remove water bourne viruses like poliovirus, hepatitis, and Norwalk, though most do not.
A water purifier kills or sterilises all living things in the water (bacteria, protozoa, giardia, cryptosporidium and viruses), either using chemicals or UV light but leaves any physical matter untouched (e.g. silt, chemical odour and taste). So although your water may be bug free it's still brown and smelly.
Clean free running water in developed countries may not need to be filtered, only purified though some ground run off may need to be filtered and possibly purified. In developing countries and areas where cattle excrement may be in the water it's best to use both systems to be sure your water is safe to drink. In this instance where the water is turbid (cloudy) it's best to filter first and then purify after as it is possible the purifier will not get to bacteria or viruses inside the particles which are making the water cloudy. This also uses less chemical purifier but does mean your purified water still has the chemicals from purification in it which can leave an after taste. With clearer water you can purify your water first and then filter it after the appropriate dwell time. This has the advantage of removing any taste or odour from the water that the purifying process may have added. You can also filter your water and then boil it strongly for at least 10 minutes, but this uses a lot of fuel and is an expensive and heavy way of purifying.
It's worth noting that not all chemicals and heavy metals will be removed by filters or purifiers. Fortunately these sorts of contaminates are usually only found in water as a by product of industry such as mining and large scale farming. Despite having a filter and purifier it is always best to obtain information about any water source.
Water Filters usually work at around 1 litre per minute, using a pump or pressure for force the water through the filter. Water purifiers take seconds to apply but the treated water normally has to be left to dwell to give the bugs time to die. For a chemical purifier this can be 15 mins to 4 hours depending on the volume and treatment used. For UV systems this it is a couple of minutes. Both filters and purifiers have their place depending on the water quality that you start with.
In order to get the right system for you, an accurate assessment of the water quality you're likely to encounter must be made. Once you know this then it's straightforward to get the right system. A summary of all the different systems strengths and weaknesses are below.
A tough filter and purifier which is able to mechanically remove all unwanted particles including bacteria, protozoa and viruses. Ideal for prolonged use in any part of the world where water will need to be obtained from any source.
Flow Rate: 2.5L/min | Cartridge Life: 10,000 litres | Type: Hand Pump
A lightweight pump action filter best for use with clear water but can be used with slightly cloudy water, though this will require frequent cleaning and will quickly reduce the cartridge life. Ideal for solo trips where safe water is not a guarantee.
Flow Rate: 0.5L/min | Cartridge Life: 7000 litres | Type: Hand Pump
A lightweight pump action filter for use with clear or cloudy water, ideal for longer trips where water quality is not guaranteed, though a replacement cartridge may be required.
Flow Rate: 1L/min | Cartridge Life: 1150 litres | Type: Hand Pump
A tiny filter with an incredible cartridge life when cleaned which also removes bacteria and protozoa. Ideal as a personal system for any trips where water quality isn't guaranteed.
Flow Rate: 1.7L/min | Cartridge Life: 375,000 litres | Type: Gravity or Squeeze Bottle
Tiny hand held filter which removes bacteria and protozoa. Ideal for those looking for something which can keep up with their fast and light pace.
Flow Rate: 1L/min | Cartridge Life: 2000 litres | Type: Palm Pump
Disinfectant tablets which are effective against bacteria, viruses and Giardia, 1 tablet per litre. For use with a clean water source or with filtered water.