Chlorine Flush FAQs

A chlorine flush is a procedure involving the application of a 12% solution of sodium hypochlorite to one or both of SSID's water tanks in order to disinfect any part of the infrastructure that may have tested positive for E.coli or coliforms.

Yes, the water will be treated with a quantity of sodium hypochlorite 12% that is within Canada's Drinking Water Guidelines.

The Operator and the persons doing tank thickness measurements will be entering the empty tank, which will require re-sterilizing after the work is finished, to prevent any coliform bacteria remaining in the tank. Coliforms can develop into increased quantities that are associated with an elevated risk of waterborne diseases, including gastroenteritis. Coliforms are living bacteria that divide and multiply, so even a small count should be prevented.

The chlorine used is a sodium hypochlorite 12% solution.

The amount of chlorine (sodium hypochlorite 12%) is variable. If applying to the 40,000-gallon lower tank, the amount would be 4x more than if applying to the 10,000-gallon upper tank, because the amount of chlorine is based on a prescribed ratio of chlorine to water at its application point, with another calculation for the residual amount to be achieved at the end of the water line. The residual goal is a range of 0.2 parts per million to 2.0 parts per million.

Run your tap for at least 5 minutes. Leave tap water on the counter in an open carafe for a few hours or until the chlorine smell dissipates. Citric acid neutralizes chlorine so a little squeeze of lemon works as well. We have received reports of a chlorine smell still detected in the water after a week. As more people use the water, the smell will dissipate.

SSID tests monthly at 8 sample stations throughout the District. All 8 samples must show less than one part per million. The water tests are posted to the Monthly Reports webpage.

At the time of the flush, it may be unknown how bacteria has entered the system. There may be instances where a part of the distribution system is failing, or that organic matter was introduced in above-water openings, or even that bacteria entered during the water sampling procedure itself, regardless of sanitary precautions.

Chlorine was flushed through the waterworks on April 15 and 16, 2023, following a tank cleaning. There is no additional plan to do a system-wide chlorine flush at this time.

Both chlorine and bleach come in several forms, so one is not exactly the other. The chlorine used in SSID flushes is a 12% solution of sodium hypochlorite. However, the smell and taste of this disinfectant does smell and taste as you might expect bleach to taste. This does not mean bleach is safe for consumption.

SSID water is untreated, except when bacteria has been detected. The aquifer water is considered pristine, so does not need treatment. The water does however have natural components, such as minerals for example. Twice per year, SSID does a full spectrum analysis.