Water Filters - what type should I use?

What type of water filter is best for home use? There are many different brands and types of water filters out there. Which one is best for you depends on where you live and what is actually in your local drinking water. For example, is it fluoridated or highly chlorinated? Are you on tank water or town water? Do you own your home or are you renting? How much space do you have for a filter? In addition, you also need to understand which filtration systems can do what.

Activated Carbon Filters

These are the cheapest and most common type of filtration system.  They absorb organic contaminants that cause bad taste and odor. Some are also able to remove chlorination byproducts, cleaning solvents and pesticides. Carbon Filters are unable to remove metals such as lead and copper, nitrates, bacteria or dissolved minerals.

Ceramic Filters

Porous ceramic allows nothing larger than water molecules to pass through it - but there are lots of chemicals smaller than water molecules.  Most microbes are blocked and colloidal silver lining helps control bacterial buildup in the water. Unless an activated carbon filter is included, ceramic filters will not remove chlorine.  Where water is relatively high in sediment, these filters become easily blocked and will not filter anything.  Regular cleaning and replacement is necessary.

Ion Exchange Units

These filters can remove minerals, in particular calcium and magnesium which make water "hard". They can remove around 50% of fluoride and some models remove radium and barium. Used on their own, don’t effectively remove bacteria.

Activated Alumina

These filters are often marketed as good for whole-of-house filtration and for removing up to 95% of fluorides. This is misleading in that they may start out as very efficient filters but once installed they get blocked easily, especially in areas of high sediment.  They cannot sustain the manufacturer's specifications unless the filters are constantly replaced, making them an expensive choice.  Furthermore, filter cartridges are usually exclusive to the manufacturer, so you are stuck with buying their replacements.  If you don't replace the activated alumina at the specified time, which is fairly short and expensive, you run the risk of the alumina breaking down and leaching aluminium into the water.  At a usage of 4 litres/day of drinking water, this filter would only last around 12 weeks.  This makes it unsuitable and very expensive for whole-of-house filtration of approx 450litres/day.

Reverse Osmosis (RO) Units

Considered the Gold Standard of filters, RO units, (should be multistage - ie a series of filters in addition to the RO membrane) remove nitrates, sodium, fluorides, heavy metals, foul tastes, smells and colors. They can reduce the level of some pesticides, dioxins, chloroform and petrochemicals. These filters utilise activated carbon as well as an ultrafine reverse osmosis membrane which only allows particles smaller than 0.0005 microns through.  They should have an additional filter following the RO membrane to re-alkalise the water.  Reverse Osmosis produces waste water - depending on the system, from around 3 to 5 litres of water is wasted for every 1 filtered.

Whole of House RO units are available but are large and expensive.  To filter properly, they require a reduction in water pressure and so the water pressure throughout the house will be lower.  The waste water will be significant, compared to just using RO for drinking water.

Distillation Units

Requiring electricity to operate, water is heated to boiling, the vapour is collected and cooled. They remove the same contaminants as RO units but can actually concentrate some pesticides and herbicides. Although effective, water distillation is not very energy efficient and produces significant heat.  The heating element is prone to early burn out.  Water can have a flat taste.