How to choose a Water Filter or Water Purifier

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 0.2 microns which includes bacteria, protozoa, giardia and cryptosporidium. Water filters do not remove water bourne viruses like poliovirus, hepatitis, and Norwalk. (A little more on viruses lifted from the MSR website - Currently, poliovirus only occurs in a few of the poorest countries. Waterborne viruses are very resilient and can survive for months in water. Viruses are generally species-specific; in other words, those that infect animals don't infect humans and vice versa. Because of this and the well maintained sewage systems in developed countries, not as many water sources are contaminated with viruses. In developing countries with little or no sewage control, the opposite is true. However, as more and more people head for the great outdoors, more rivers, lakes and streams are at risk of viral contamination.)

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.

Water Filters work at about 1 litre per minute, either using a pump or gravity. Water purifiers take seconds 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 is a couple of minutes. Both filters and purifiers have their place depending on the water quality that you start with.

Clean free running water in developed countries may only need to be purified, where as some ground run off may need to be filtered. In developing countries and areas where cattle excrement may be in the water it would be advisable to use both systems to be sure your water is safe to drink. In this instance you can purify your water first and then filter it after the appropiate dwell time. This has the advantage of removing any taste or odour from the water that the purifying process may have added. Or you can filter first and then purify after which uses less chemical purifier but does leave an after taste. 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.

So in order to get the right system for you, an accurate assesment of the water you will need to drink must be made. Once you know this then it's straightforward to get the right system. A summary of all the differents systems strengths and weaknesses are below.

	MSR Miox - A battery operated water purifier. Some untreated water is put in this small purifier, then mixed oxidents (MIOX, created using salt and electricity) is added. This small amount of water is then mixed with the whole body of water to be purified. The MSR Miox can treat 4 litres of water with each preparation. Dwell time is 30 min for Giardia and 4 hours for Crytosporidium. Advantages - The MIOX is tiny, like a fat pen, weighing 99g, but can be used to treat large volumes of water. It uses rock salt and batteries so can be easily replenished. 2 x CR123 3V batteries and a small amount of salt will purify 200 litres of water. No pumping and no cleaning required. A great item for a disaster kit. Disadvantages - Long dwell time for complete purification. Does not remove silt.
	Steripen Adventurer Opti - A battery operated water purifier. The Steripen uses UV radiation to render the viruses, bacteria and protozoa sterile and unable to reproduce. So although you consume some live bacteria, they are unable to reproduce inside you and make you sick. Stick the bulb in your water bottle and activate the light. Very simple. Uses 2 x CR123 3V batteries which will purify about 100 Litres. Advantages - Only 15cm high and weighing 100g. Purifies 1 Litre in only 90 seconds. No pumping or cleaning. Disadvantages - Does not remove silt. Can only treat 1 litre at a time.
	MSR Mini Works EX - Ceramic and charcoal water filter. Pumps water through the filter cartridge, removes everything but viruses. This is an MSR expedition product so can be completely stripped, cleaned and serviced in the field without tools. Advantages - Long lasting (about 2000 Litres per cartridge), tough and field maintainable. Compatible with MSR and Nalgene containers. Removes tastes and odours from chemical pretreatment (if used). Disadvantages - Does not remove viruses. Quite heavy at 456g.
	MSR Sweetwater Microfilter - Silica water filter. Pumps water through silica cartridge, removes silt, bacteria and protozoa. Filters at over 1 litre per minute. Compact and lightweight. Ideal for backcountry use in developed countries. Advantages - Light and small at 320g for a filter. Simple to use. Great for western countries. Great value. Removes tastes and odours from chemical pretreatment (if used). Disadvantages - Does not remove viruses. Average cartridge life is only 750 litres. Field cleanable but not field servicable.
	MSR Sweetwater Purifier System - Chemical Purifying and Silica water filter - This is actually the same filter system as the Sweetwater Microfilter but with the addition of a purifying solution, stainless steel prefilter and some other useful bits. MSR recommend that you filter first and purify after in order to use less purifier solution (food grade chlorine). This does leave a slight tap water taste. Advantages - Complete treatment of water, kills everything we know about so far. Light and small at 320g for the filter and 80g for the purifier solution. Simple to use. Disadvanatges - Average cartridge life is only 750 litres. Field cleanable but not field servicable.
	Aquapure Traveller Bottle 2 - Mechanically Advanced Disinfection technology allows for instant filtering. Removes viruses bacteria and pathogens including Cryptosporidium & Giardia. This system mounts the filter into a drinking bottle for a personal solution. Very simple and effective even in developing countries. Filters last approx 350 litres. No hoses, pumps or extra bottles needed Advantages - Complete treatment of water, kills everything we know about so far. Very light and compact. Simple to use. Excellent value Disadvanatges - Only filters 750ml at a time. No good for group or volume use. Not field maintainable
	Aquapure Traveller - Chemical purifier and water filter. This system mounts the filter into a drinking bottle for a personal solution. Very simple and effective even in developing countries. Fill the bottle with water to be purified and shake. This releases Iodine into the water to kill viruses. Dwell time 15mins. Once this time is up, squeeze the bottle to force the water through the 0.2 micron filter which removes all particles and the iodine taste. Filters last approx 350 litres. No hoses, pumps or extra bottles needed Advantages - Complete treatment of water, kills everything we know about so far. Very light and compact. Simple to use. Excellent value Disadvanatges - Only filters 750ml at a time. No good for group or volume use. Not field maintainable
	Aquapure Inline Filter - 0.2 Micron water filter designed to be inserted into the drinking tube of a hands free drinking system. Excellent system for filtered water on the move without lots of extra kit. Includes quick disconnect system so reservoir can be used with or without the filter. Filters last approx 350 litres. Advantages - Very small and light, only 140mm long and 106g. Simple. Do not have to stop to filter water. Disadvantages - Does not remove viruses. Not field maintainable.