Health Canada wants to see any water filter claim backed up by certification. And many products are certified. In fact, all three products we looked at for E. coli reduction are certified to reduce chlorine and make your water taste and smell better.

The Doulton ceramic filter is also certified to reduce lead and other harmful contaminants.

But certification is voluntary. In Canada there are no regulations to protect you. So what should you look for if you're shopping for a water filter?

There may not be any regulations in place to protect you, but there are some hints you can follow to make sure you're getting the right filter.

Marketplace asked Dr. Barry Thomas, toxicologist formerly with Health Canada, what consumers should look for when buying a water filtration system for the home.

The most common water filtration systems use activated charcoal filters. This is the least expensive option. Filters are used either in a jug or are screwed onto a tap. Not recommended for people who draw their water from wells.

There are literally hundreds of products sold across the country to filter home drinking water. Finding the right one for you will take a little bit of research.

"The first thing you have to do," according to Thomas, "is to decide whether you actually need a drinking water treatment device. So probably the first question is, is there a problem with your water?"

The only way to answer that is to have your water tested. Who you speak to and what it will cost are different across the country. (See our guide.)

Check the Label

Once you've determined that you need a water filtration system, the first thing to do is check the label. Make sure the product is certified.

There are three main organizations that certify water filtration products: the CSA, Underwriters Laboratory and NSF, which certifies more products with more rigor than any other company.

Does your system measure up? There are several organizations that certify water filtration devices. NSF International: widely regarded as the authority on the certification of water filtration devices. This not-for-profit organization has been developing standards for more than 50 years. Complete list of NSF certified water filtration products CSA International: not-for-profit organization established in 1919. Tests and sets standards for a wide variety of products Underwriters' Laboratories: set up in 1894, this not-for-profit organization tested nearly 60,000 products in 1999.

Still, you must read the label carefully. Not all NSF standards are the same.

There are six NSF standards for drinking water. Some are certified for health effects, such as removing lead from water. Others are for aesthetic effects, such as improving taste and odour. The six are:

Ceramic filters

Systems that use ceramic filters are installed under a sink and are attached to one faucet. They are substantially more expensive than the simple filters that are attached directly to the faucet or used in a refillable jug.

Ceramic filters are also high maintenance. They are fragile and need to be cleaned regularly. Often they are teamed up with activated charcoal or cloth filters to remove materials such as lead.

Reverse Osmosis

These systems can either be installed under a sink - or at the point where the water line enters your home. However, they are more often installed where the water enters the home.

A reverse system forces water through a membrane. One drawback is that a lot of water is wasted.

Reverse osmosis systems vary widely in price. But you can expect to pay at least several hundred dollars.

These systems work by forcing water through a small membrane which collects and contains bacteria and minerals.

Unfiltered water stays on one side of the membrane. Filtered water passes through to the other side.

The main disadvantage to this type of system is that there's always more untreated water than treated - so you end up wasting a lot of water.

Distilled water systems

An ultraviolet system relies on UV rays to kill bacteria in water. Does not remove contaminants like lead. Should be used in conjunction with activated charcoal system.

Like reverse osmosis systems, distilled water units can be installed either at the point of entry or at the faucet where you get most of your drinking water. Most systems tend to be installed at the faucet.

These systems also tend to vary widely in price and will run at least several hundred dollars.

Distilled water filtration systems work by heating water to boiling, then cooling and condensing it back to liquid form. That leaves behind all minerals and bacteria.

These systems use a lot of electricity, making them more expensive to operate than some other systems.

Ultra violet light

Systems that rely on ultra violet light do not rely on filters. They are actually disinfection systems. UV devices are installed where the water comes into your home. You can expect to pay at least $500 for a basic UV system.

These devices work by shooting UV light at the water, killing bacteria. They do not get rid of lead or other minerals, so you would still need some type of activated charcoal system to work in conjunction with a UV system.

Boiling

There have been a lot of "boil water orders" across the country. Boiling water is the cheapest way to kill bacteria in your water. It is also very effective.

However, Thomas warns, people should be aware that boiling will only disinfect water. For problems like lead, boiling will actually concentrate it.