Comparing Home Water Filters

Learn how five basic systems work to find the one that’s right for your household

We use it to cook, clean and wash. But how safe is the water coming into our homes?

Problems with drinking water contaminated with E. coli, coliform bacteria or lead have left many of us worried. A home water filter may be the simplest solution for ease of mind and to safeguard against potential contamination. But with so many products on the market how can you find the one best suited for your home?

Know your water

Start off by finding out what contaminates are in your water since this can determine what kind of filter you buy. Americans can get their local water contamination report online at the EPA website. Canadians will have to ask their municipality for the report since there is no central bank of information.

If you can't find your municipal report you may want to get your water tested by an independent analytics laboratory. The Canadian Association for Environmental Analytical Laboratories (CALA) offers an online directory for laboratories. Whichever lab you choose, be sure to look for the International Laboratory Accreditation Cooperation (ILAC) certification for following the ISO 17025 international standard.

Two systems

Most of us are going to want to filter out heavy metals and bacteria. Water filters come in two kinds:

  • Point-of-entry units/whole house: treats water before it gets distributed throughout the house. These systems are more sophisticated but also more expensive and require regular maintenance by a service technician.
  • Point-of-use units: treats water after it's out of the faucet, include countertop filters, faucet filters, and under-the-sink units. These systems vary is price and performance.
  • There are five basic types available:

  • Activated carbon filters
    Found in: Countertop, faucet filters and under-the-sink units.
    Filters: Bad tastes and odours, including chlorine. Can also reduce heavy metals such as copper, lead and mercury; parasites such as giardia and cryptosporidium, pesticides, radon, VOCS, MTBE, TCE.
    How it works: Positively charged and highly absorbent carbon in the filter attracts and traps impurities as the water passes through.
    Pro: Affordable and easy to find.
    Con: Ongoing cost of replacing carbon filters, filters not easily recycled, plastic pitchers may leach Bisphenol-A (BPA) into filtered water.
  • Ceramic water filters
    Found in: Countertop filters.
    Filters: Bacteria, heavy metals, tetrachloride, chlorobenzene, mercury, iron, zinc, toxaphene, chlordane, radon, lindane, simazine, PCB's, VOCs, MTBE, TCE, toluene, xylenes, lead, copper, cadmium, chlorine.
    How it works: Uses cleansing properties of clay combined with diatomaceous earth. Water first passes through the ceramic chamber and filters into a lower chamber coated with silver.
    Pros: All natural ingredients, extremely environmentally friendly, no waste.
    Cons: Not recognized by NSF, hard to find, slow process to filter water.
  • Distillation
    Found in: Whole house units, countertop.
    Filters: Heavy metals such as cadmium, chromium, copper, lead and mercury, arsenic, barium, fluoride, selenium and sodium.
    How it works: Water is boiled and the purified steam condenses back into water.
    Pro: Gets rid of most impurities.
    Con: Hard to find, works slowly, uses a lot of electricity, removes good trace elements including oxygen which can make water taste flat.
  • Reverse osmosis
    Found in: Whole house or under-the-sink units; often in combination with a carbon filter or UV disinfection unit.
    Filters: Most contaminants, including Cryptosporidium and Giardia parasites, heavy metals such as cadmium, copper, lead and mercury; arsenic, barium, nitrate/nitrite, perchlorate and selenium.
    How it works: Water goes through a semi permeable membrane that impurities can't penetrate.
    Pro: Finely filtered water.
    Con: wastes water, extremely slow, membrane must be chosen according to water, requires professional installation, does not filter out all impurities so must be combined with other filters.
  • Ultraviolet disinfection
    Found in: whole house units and under-the-sink units.
    Filters: bacteria and parasites; some heavy metals.
    How it works: uses a high frequency light to irradiate water.
    Pro: excellent sterilizing system.
    Cons: impossible to know if the system is working, whole hour units are more expensive and will require regular maintenance.
  • Do your homework

    After deciding what type you would like to buy then do some research to find a brand that works for you. The National Sanitation Foundation (NSF), the most respected authority on water filters, has a data base of products it has tested. Compare what your chosen system claims it does against what the NSF has found. 

    Other companies who have done their homework:

  • Water Filter Comparisons
  • Consumer Search Water Filters review
  • The Green Guide Water Filters
  • Consumer Reports (subscription required)
  • Mihira Lakshman is a Toronto based freelance writer who enjoys a glass of cool water every now and then.