Do you know what's in your drinking water? Finding out could be the key to picking the best filters. [Photo: Bigstock]

Q&A: What’s the best type of water filter?

12 August, 2014

Q — I’d like to buy a water filter but am confused about which type is best. Can you help me understand more about this?


A — We need clean water to live and thrive but many people these days worry about whether the water that comes out of the tap is as clean as it (usually) looks.

It’s not an idle fear. Studies and surveys consistently show that our tap water can contain many chemicals known to damage health.

In 2009 an investigation by The New York Times found that, in the previous 5 years some 62 million people in the US had been exposed to drinking water contaminated with thousands of chemicals – albeit in low concentrations – that are not regulated under federal law.

In 2013 another survey by the US Geological Survey and the Environmental Protection Agency found traces of 18 unregulated chemicals were found in drinking water in a nationwide sampling. These included 11 perfluorinated compounds, an herbicide, two solvents, caffeine, an antibacterial compound, a metal and an antidepressant.

In the UK in 2013 a water quality survey by the Environment Agency found the slug poison metaldehyde in 1 in 8 rivers and reservoirs used for drinking water in England and Wales.

Water contamination chart

The 2013 USGS/EPA survey found many unregulated chemicals in drinking water

What to do?

Stories like this led initially to a surge in sales of bottled waters.

But bottled water may be more convenient, but it is definitely not sustainble because it is associated with numerous environmental concerns, including the generation of billions of wasteful plastic bottles, the burning fossil fuels to refrigerate and transport those bottles, and the draining of aquifers and watersheds to fill the bottles.

Plastic bottles can also leech chemicals into the water, especially if they are stored for long periods at high temperatures.

This in turn has led to an interest in water filtration systems and ongoing debate about which type is official the “best”. 

The truth is there is no “best”. There are benefits and limitations in every type of water you choose to drink. Most water filtration systems can reduce but not entirely remove all harmful industrial chemicals, pesticides, heavy metals, parasites and other nasties.

Know your local water supply

Water filters are great to improving the overall taste, smell and appearance of drinking water and most can remove or reduce levels of harmful industrial chemicals, pesticides, heavy metals, parasites and other nasties.

But it’s important to select a water filtration that is suitable for whatever you have in your local water supply. If, for example, your area is high in lead, you need one that is certified to remove lead.

In the US you may be able to find out what’s in your water by logging on to the  Environmental Protection Agency (EPA)’s Web site. In the UK local water companies should provide customers with a free report on water quality in their areas on request. The Drinking Water Inspectorate has a list of contact details for local water companies.

Once you know what’s in your water then you can figure out which filter is best for you.

In the US, the National Sanitation Foundation (NSF) produces a comprehensive   Contamination Guide, which gives an indication of the effectiveness of different types of filters based on the particular contaminant.

The Environmental Working Group’s What’s in your water? website also contains information on different types of filtration and has a handy interactive tool for finding the best filter for your needs.

You don’t need to spend a fortune

We summarise the pros and cons of some of the most common types of water filter below, but what is clear is that you don’t always have to spend a lot of cash to get results.

 For instance, a team at Universite Laval in Quebec City researched ways to cut down on trihalomethanes (THMs) and haloacetic acids (HAAs) the two main byproduct chemicals produced when chlorine used to disinfect tap water reacts with the organic matter normally present in it.

THMs and HAA are thought to increase the risk of liver, bladder and kidney cancer.

The researchers tested three common forms of household treatment on tapwater from the Quebec city area.

Storing water in a refrigerator for 48 hours reduced THMs by 30%, while boiling water before storage cut them by 87%. Using an activated carbon filtering pitcher however, cut levels by 92%.

Direct storage and boiling had no effect on HAAs, but filtering was found to reduce them by 66%.

So simply using a counter top filter may be a good all round choice for you.

The pros and cons

The quality of water we drink is almost as important as the quantity.

No filter will remove every contaminant, in part because the list of risky chemicals keeps growing.  But here are the most common types of filters and the major contaminants they are designed to trap:

Carbon filters include countertop pitchers, faucet-mounted models, undersink models (which usually require a permanent connection to an existing pipe), and whole-house or point-of-entry systems (usually installed in the basement or outside). Carbon, is a porous material that absorbs impurities as the water passes through.  Smaller filters are very affordable and generally use granules of activated carbon. Larger more expensive units use solid block carbon. The latter is likely to be more efficient.

Both types need replacing regularly and if left too long counter top filters need replacing regularly or they can become reservoirs for bacteria Carbon filters do not remove heavy metals, herbicides, pesticides, fluoride, or endocrine disruptors. What it’s good for: Lead, PCBs, chlorine byproducts (chloramines and trihalomethanes), certain parasites, radon, pesticides and herbicides, the gasoline additive MTBE, the dry-cleaning solvent trichloroethylene, some volatile organic compounds, some levels of bacteria (such as Cryptosporidium and Giardia) and a small number of pharmaceuticals.

Reverse-osmosis systems push water through a semipermeable membrane, which acts as an extremely fine filter. They’re often used in conjunction with carbon filters which must be replaced regularly. They can be expensive and the waste 4 to 9 gallons (15 to 34 litres) of water for every gallon (3.8 litres) filtered. This is increasingly unacceptable in a world where water is becoming scarce. In addition reverse osmosis filters can also take out beneficial minerals from the water along with less desirable elements (something they have in common with distillers). This type of filtration does not remove endocrine disrupting chemicals. What it’s good for: Chemicals carbon filters may miss, including perchlorate, sulfates, fluoride, industrial chemicals, heavy metals (including lead), chlorine byproducts, chlorides (which make water taste salty), and pharmaceuticals.

Ultraviolet light units expose water to strong UV radiation. Countertop units can bought relatively cheaply but whole house units can be pricey. They can’t remove endocrine disruptors, VOCs, trihalomethanes, asbestos, lead or mercury and may not remove cryptosporidium. What it’s good for: Bacteria and viruses. Some experts recommend using them with carbon filters to remove a broader range of contaminants.

Ozonation In this type of system ozone gas is injected into water injected as tiny bubbles in water. This precipitates and then filters our materials such as iron, sulfur and manganese out of the water and because ozone is also antibacterial helps kill bacteria as well. Units can be expensive and unless well maintained the process can also create some harmful disinfection byproducts (DBPs)  if chemicals like bromine and formaldehyde are present in the water. What they’re good for: A very effective disinfectant that kills most organic contaminants. Breaks down and oxidizes most organic chemicals that cause taste and odour problems.

Distillers, boil and condense water. While countertop units are available, distillers use lots of electricity, generate excess heat, and require regular cleaning. Explore filters or other alternatives to remove your contaminants, or, in a pinch, buy distilled water.  What it’s good for: Heavy metals (including lead), particles, total dissolved solids, microbes, fluoride, lead, and mercury.

Remember also that, if you have confidence in your local water supply, tapwater does have multiple benefits – the main one being that it is almost always available. In addition, if you get into the habit of drinking only bottled water, you can easily reach a point where you believe that when the bottle is empty, you’ve run out of water!

Most of us don’t get enough water on as daily basis, so once you’ve decided on the type of filters you want and need, don’t forget to DRINK!