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Interpretation of Water Testing Results

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BACTERIOLOGICAL WATER TEST

The Provincial Laboratory for Public Health tests private water supplies for the presence of both total coliform (TC) and Escherichia coli (E. coli) which are indicators of well contamination.

Total coliforms include bacteria that are always present in animal waste and human sewage. However, they are also found in soil and vegetation. Their presence (in the absence of E coli) may indicate that surface water is entering your well, or that your well or another part of your water system is colonized by bacteria and needs cleaning.

E. coli are found only in the digestive systems of humans and warm-blooded animals. The presence of E. coli in your water supply is usually the result of human or animal waste contamination from a nearby source. Some examples of contamination sources include domestic or wild animal activity near the well or cistern (e.g. gopher holes, deer, mice, birds, dogs, cows, sheep, llamas, etc.); manure storage; manure spreading; onsite septic systems and lagoons (especially if malfunctioning); and surface water such as rivers, streams, lakes and flood waters.

The result of one water sample is not a reliable indicator of the safety or contamination of your well or other private water supply. The results of water samples that you submit may vary because the levels of total coliforms and E. coli that are collected from your water can vary with the time of day, time of year, and even between samples taken at the same time.

It is recommended that you collect three consecutive samples in total, taken 1-3 weeks apart, to establish the safety of water from your water supply.

The initial water sample that you submit will undergo a test that only determines the presence or absence of total coliforms and E coli bacteria. If the initial sample that you submit contains total coliforms and/or E coli, you will be advised to submit more samples to confirm the initial result. If you decide to submit re-samples, the lab will use another method that actually counts the number of bacteria that are present in 100 milliliters of your water sample.

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The numbers of bacteria will indicate a small or large amount of contamination. Knowing the number of bacteria is also useful for identifying trends in the water contamination over time, with well treatments such as shock chlorination, or with changes in the weather (e.g. numbers of bacteria increase after heavy rain). This information helps in understanding what is happening and help narrow down the source of the contamination.

Interpretation of Bacteriological Results

The Provincial Laboratory of Public Health performs laboratory tests on well water samples. Initially the laboratory looks for whether bacteria are present or absent in a sample. The presence of certain types of bacterial indicators such as E-coli or Total Coliforms can be an indication that your water is unsafe to drink.

If your well water sample result shows the presence of E-coli or Total Coliforms, you will be contacted by a Health Inspector to discuss these results and what further actions should be taken.

The following definitions will help you interpret your report:

Definitions:

  • Absent:Indicates bacteria were not identified in the well water sample tested.
  • Present:Indicates bacteria were identified in the well water sample tested.
  • E-coli:The presence of E-coli in a well water system indicates it has recently been impacted by fecal contamination and should not be considered safe to drink. This situation should be discussed with the Health Inspector who can make recommendations about boiling your water or other treatment methods.
  • Total Coliforms:The presence of Total Coliforms in a well water system are indications of possible surface contamination of the water supply. Total Coliforms may also indicate inadequate water treatment practices. This situation should be discussed with the Health Inspector who can make recommendations on what further action you should take.

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CHEMICAL WATER TEST

The University of Calgary’s Centre for Toxicology tests samples from private water supplies for levels of some common inorganic compounds and other water quality parameters. Below is a list of the results you will receive in your routine chemical water analysis report, along with an explanation of what each result means.

The Guidelines for Canadian Drinking Water Quality provides maximum limits for substances in drinking water that can be harmful to your health. For your protection, the maximum limits are set below the levels at which any harmful health effects have actually been observed. The substances listed in your chemical water quality report that have a maximum health limit set by the Guidelines for Canadian Drinking Water Quality include sodium, fluoride, nitrate and nitrite.

Many of these test results are not significant to human health. Many of the limits provided below describe water quality conditions (e.g. total hardness, sulphate, iron) that are best for various household uses and for aesthetic reasons such as taste, smell, and appearance of the water.

The amount of a substance in your water sample is described as milligrams per Litre (mg/L), which is equivalent to parts per million (ppm).

The test results for Conductivity, Cation / Anion Sum, Ion Balance, % Difference are for laboratory work purposes only.

Parameter (limit)

Description

  • pH (6.5 – 8.5)
    Measure of hydrogen ion concentration in water. Corrosion of metal plumbing and appliance parts may be a problem below pH 6.5. Scale formation (mineral deposits) on pipes, cookware and appliances may be a problem above pH 8.5.
  • Sodium (200 mg/L )
    Sodium in drinking water should not exceed 20 mg/L for people on sodium-reduced diet for conditions such as hypertension, congestive heart failure or heart disease. If in doubt consult your physician. Over 200 mg/L will give water a salty taste, but poses no significant risk to people in good health.
  • Potassium (No guideline)
    Potassium at levels of 50 to 100 mg/L may contribute to corrosion and scaling.
  • Calcium (No guideline)
    Calcium is good for human health. Calcium contributes to water hardness.
  • Magnesium (No guideline)
    Magnesium is essential for human health but can cause a laxative effect at high concentrations (See Sulphate). Magnesium contributes to water hardness.
  • Total Hardness (80 to 100 mg/L)
    Water hardness results from the calcium, magnesium, and other minerals that water collects as it moves through the ground. Water hardness is characterized as follows: soft, 0 to <60 mg/L; medium hard, 60 to <120 mg/L; hard, 120 to <180 mg/L; and very hard, 180 mg/L or more. Soft water can contribute to corrosion while hard water contributes to scaling on pipes, water heaters and appliances. Hard water also requires more soap during washing. Water softeners will reduce hardness to acceptable levels, but will increase sodium levels (see sodium).
  • Iron (0.3 mg/L)
    At concentrations above 0.3 mg/L, iron can leave a reddish-brown stain on laundry and plumbing fixtures and produce undesirable tastes in beverages. High iron levels also encourage the growth of iron bacteria, which can grow in your well causing deterioration of well, water system components and plumbing. Shock chlorination is an effective means of controlling iron bacteria (this procedure may have to be repeated annually). In severe cases, an iron filter may be required.
  • Total Dissolved Solids, TDS (500 mg/L)
    TDS is the approximate concentration of inorganic & mineral substances dissolved in the water. High TDS can cause scaling and affect water’s taste and smell. Low TDS can give water a flat taste.

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Parameter (limit)

Description

  • Total Alkalinity (No guideline)
    Alkalinity is formed by bicarbonate, carbonate and hydroxide. Alkalinity affects water characteristics and treatment processes. Lower levels of alkalinity contribute to corrosion while higher levels contribute to scale formation.
  • Fluoride (1.5 mg/L)
    Fluoride levels over 1.5 mg/L may increase the risk of a condition known as dental fluorosis (mottling of tooth enamel) in children with developing teeth (newborns to age thirteen). Lifelong exposure to high levels of fluoride in drinking water has been linked to an increased risk of developing skeletal fluorosis later in life.

    Fluoride can be removed from drinking water by point-of-use devices such as reverse osmosis or distillation.
  • Carbonate, Bicarbonate & Hydroxide (No guideline)
    Carbonates, bicarbonates and hydroxides are associated with water’s alkalinity, salinity, and the amount of total dissolved solids. Higher levels of bicarbonates can contribute to scale formation.
  • Nitrate-Nitrogen (10 mg/L)
    Nitrate as NO3 (45 mg/L)
    Nitrite as NO2 (3.2 mg/L)

    Nitrate and nitrite concentrations above limits in drinking water can cause a condition known as methaemoglobinaemia, or blue baby syndrome, in susceptible people including pregnant women and infants less than 6 months of age. Blue baby syndrome decreases the ability of the blood to carry oxygen and is a serious, life-threatening condition for infants.

    If these limits are exceeded, human and/or animal wastes contamination should be suspected and an investigation carried out to determine the source.

    Nitrates and nitrites can be removed by point-of-use devices such as distillation and reverse osmosis.
  • Sulphate (500 mg/L)
    Sulphates can occur either naturally in water or from the decomposition of plants, animals and organic wastes. Ground water that contains natural concentrations of sulphates may also contain sulphate-reducing bacteria which change sulphates to hydrogen sulphide (a gas with a “rotten egg” odour). Sulphate-reducing bacteria can also cause corrosion problems. Aeration or chlorination with filtration will reduce hydrogen sulphide in well water.

    High levels of sulphate may have a laxative effect on new users. Regular users tend to become accustomed to high sulphate levels.
  • Chloride (250 mg/L)
    Chloride may begin to affect the taste of water and beverages at 200 mg/L. High levels of chloride can contribute to either corrosion or scale formation, depending on water quality. A sudden increase in chloride levels may indicate pollution of your water supply by an external source (e.g. road salt, irrigation drainage).

If you have further questions regarding the results of your water analysis, or if you would like information on water treatment, please contact your local public health inspector by clicking here.

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