Turbidity is a water quality term that refers to fine suspended particles of clay, silt, organic and inorganic matter, plankton, and other microscopic organisms that are picked up by water as it passes through a watershed.

Which water sources are most affected by turbidity?
Turbidity levels are much higher in water from surface water sources (e.g. streams, rivers, and lakes) than from groundwater sources. Some surface water sources exhibit high turbidity levels during periods of high precipitation or snow melt (e.g. spring runoff).

How is turbidity measured and reported?
Turbidity, which is measured and reported in nephelometric turbidity units (NTU), is an optical measurement of water’s ability to scatter and absorb light rather than transmit it in straight lines. Turbidity levels can range from less than 1 NTU to more than 1,000 NTU. At 5 NTU water is visibly cloudy; at 25 NTU it is murky.

How often is my water tested, and for what?
Water intended for drinking is measured against physical, chemical, radiological, and microbiological standards outlined in the federal Guidelines for Canadian Drinking Water Quality. To that end, your water is tested regularly for viruses, bacteria (e.g. E-coli), parasites (e.g. Giardia and Cryptosporidium), and turbidity. The guidelines recommend that water intended for drinking have a turbidity level < I NTU.
How will elevated levels of turbidity be reported?
In keeping with the Guidelines for Canadian Drinking Water Quality and B.C.’s Drinking Water Protection Act, water suppliers will notify customers of turbidity levels that exceed 1 NTU. A Turbidity Index on the supplier’s website will indicate if the water is ‘Good’ (< 1 NTU), ‘Fair’ (1-5 NTU), or ‘Poor’ (>5 NTU), and provide recommendations for each. ‘Fair’ and ‘Poor’ ratings will also be publicized through the media. To subscribe to an automatic email notification service, please contact your water utility.

Is turbidity a health concern?
Turbidity is not so much a health concern as an indicator of health risk. Science has proven that as turbidity increases, the risk to human health also increases—particularly for at-risk populations such as newborns, the elderly, and people with compromised immune systems (e.g. those with HIV/Aids, undergoing chemotherapy, or taking anti-rejection drugs.)

Why is turbidity an important water quality indicator? 
Bacteria, viruses, and parasites such as Giardia and Cryptosporidium can attach themselves to the suspended particles in turbid water. These particles then interfere with disinfection by shielding contaminants from the disinfectant (e.g. chlorine). Nor is chlorine effective in deactivating Cryptosporidium.

What are accepted water-industry standards for turbidity, and who sets them? 
Health Canada’s Guidelines for Canadian Drinking Water Quality recommend that surface water suppliers aim for turbidity levels <1 NTU at the point of disinfection. The guidelines state that a water supplier with turbidity levels > 1 NTU should notify the public of the increased health risk, and that a turbidity level > 5 NTU should trigger a Boil Water Notice. The guidelines also recommend filtration for water from all surface water sources, and specific water quality parameters for each type of filtration used. These standards are reflected in B.C.’s Drinking Water Protection Act, and advocated by IH in its 4-3-2-1-0 treatment objectives.

What are Interior Health’s 4-3-2-1-0 treatment objectives?
In 2004—after carefully examining B.C.’s Drinking Water Protection Act, the Guidelines for Canadian Drinking Water Quality, and standards set by the U.S. Environmental Protection Agency—IH defined new water treatment goals for water suppliers within its region. The 4-3-2-1-0 treatment objectives recommended 4-log (99.99 percent) inactivation and/or removal of viruses, 3-log (99.9 percent) inactivation and/or removal of Giardia and Cryptosporidia, dual treatment (e.g. filtration and disinfection), <1 NTU turbidity, and 0 total or fecal coliforms.

Who is responsible for ensuring my drinking water is safe? 
In keeping with B.C.’s Drinking Water Protection Act, Interior Health is responsible for overseeing source-to-tap assessments of all drinking water systems, and monitoring operational standards, including turbidity testing, monitoring, reporting, and public notification. IH’s Drinking Water Team (in its Health Protection Division) works closely with the region’s 1,300 water suppliers to ensure compliance with the act and corresponding regulations. As outlined in the act, IH requires each water system serving more than 300 connections to:

  • employ certified operators;

  • undertake a drinking water sampling program;

  • conduct continuous on-line turbidity sampling and recording of raw water for each surface source;

  • conduct continuous online monitoring of the disinfection process;

  • perform Giardia performance monitoring as prescribed by the public health engineer;

  • implement a cross-connection control program;

  • develop well protection plans for each well source;

  • review and update emergency response plan annually;

  • provide long-term plans for source, treatment, and distribution system improvements; and

  • report prescribed monitoring results to the public health engineer monthly.

And, as also required by the act, IH staff are working with water suppliers via the Turbidity Education and Notification Campaign to ensure customers are aware of potential health risks posed by increased turbidity, and are informed of turbidity spikes that may compromise their health.

How do Interior Health and my water supplier respond to elevated turbidity levels? 
Surface water suppliers serving more than 300 connections are required by IH to monitor and report turbidity levels on an ongoing basis. If turbidity levels rise above the federally recommended level of 1 NTU, a water supplier must notify IH, monitor bacteriological levels and chlorine residuals within the distribution system, and notify customers of increased health risks using the Turbidity Index. If turbidity levels exceed 5 NTU, and if IH deems it necessary, the water supplier will initiate an Emergency Response Plan. The public will be notified of the resulting Boil Water Notice via the water supplier’s website and through the media.

What precautions should I take if the water is turbid? 
The Province of B.C. recommends that newborns and people with compromised immune systems drink boiled water or safe alternative at all times if they’re served by an unfiltered surface water source. When turbidity levels range from 1-5 NTU, IH and water suppliers recommend that children, the elderly, people with compromised immune systems, and anyone seeking additional protection drink boiled water or a safe alternative. When turbidity levels exceed 5 NTU, IH and water suppliers recommend that all users drink boiled water or a safe alternative.

How can I protect my children?
IH and water suppliers recommend that newborns (up to six months) drink boiled water or a safe alternative at all times. They also suggest that children drink boiled water or a safe alternative if turbidity levels exceed 1 NTU. You can provide them with water that has been boiled (at a rolling boil) for at least one minute, bottled or distilled water, or water that has been filtered through a well-maintained treatment device. You might also want to inform that there is a far greater risk of gastrointestinal illness from poor hygiene (e.g. not washing their hands well and often).

How do I boil my tap water to make it safe for drinking?
Water must be boiled (at a rolling boil) for at least one minute and then stored in a clean, covered container in the fridge.

What are safe alternatives to tap water? 
Safe alternatives to tap water include bottled or distilled water, or water filtered through a well-maintained in-home treatment device.

  1. Point-of-entry systems treat all water entering your home. They effectively remove colour, sediment, and minerals. Activated-carbon backwashing filters work well, as do reverse osmosis and filtration systems, which also remove or inactivate parasites such as Giardia and Cryptosporidium.
  2. Point-of-use systems treat water intended for drinking or cooking. Usually hooked into the kitchen faucet or installed below the sink, they treat water using reverse osmosis, carbon filtration, or distillation. Point-of-use systems that remove particles one micron or less in diameter are effective against parasites. Filters in this category include those using reverse osmosis, those labeled as ‘absolute’ one-micron filters, and those certified by NSF International under NSF Standard #53 for cyst removal.

    Whatever system you choose, follow installation and maintenance directions carefully. Poorly-maintained units can actually pose serious health risks. IH can provide you with information about bottled water and other alternatives.

    Can I get my point-of-use water treatment device tested?
    Yes. Testing is available at private analytical laboratories. Bacteriological testing is about $40; chemical testing is about $300.

    Is bottled water safe?
    In Canada, bottled water products are considered food items and, as such, are monitored by the Canadian Food Inspection Agency. Members of the Canadian Bottled Water Association are also subject to the standards of the association. Bottled water plants in B.C.’s interior are inspected by IH public health staff.

    Are grocery store water systems tested?
    Yes. IH conducts bacteriological testing on grocery store water systems at least twice a year.

    How long can I keep bottled water?
    Water can support microbial growth, and like any other product has a shelf life. Shelf life depends on the type of water bottled and the treatment methods used. You can consult with bottled water companies about the shelf lives of their products.

    Should bottled water be refrigerated?
    As water can support microbial growth, bottled water should be refrigerated once it’s opened.

    Will my coffee maker purify the water?
    No. The coffee filter may remove some turbidity and the heat may kill some bacterial, but neither Giardia nor Cryptosporidium will be removed or inactivated.

    Is it safe to brush my teeth with turbid water?
    Yes, unless a Boil Water Notice is in effect.

    Is it safe to wash my vegetables in turbid water?
    Yes, unless a Boil Water Notice is in effect.

    Is it safe to bathe or shower with turbid water?
    Yes, but children should be discouraged from drinking bath water or chewing facecloths.

    If you are interested in getting water quality notices by email, complete the email submission form on the bottom of our Home Page and be sure to tick the "Yes I would like to receive Water Quality Notifications" box.