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
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
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
- employ certified operators;
- undertake a drinking water sampling
- 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;
a cross-connection control program;
- develop well protection plans
for each well source;
- review and update emergency response plan
- 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
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 two minutes
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
- 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.
- 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
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.