The information provided here has been simplified and is offered for educational purposes only.
Why is the water supplied to our homes sometimes yellowish or brownish?
Water drawn from deep wells, as is the case in the Town of Saint-Lazare, naturally contains metallic element such as iron and manganese. These elements are usually not oxidized since they have had little or no contact with oxygen.
Although the non oxidized manganese and iron contained in water drawn from deep wells are naturally colourless, they take on a yellowish or brownish tinge when in contact with the permanganate (Saddlebrook treatment plant) and the sodium hypochlorite (Saddlebrook and Sainte-Angélique treatment plants) used as precipitating and disinfecting agents. This change in colour is caused by the oxidizing ability of both these products.
When iron and manganese are oxidized, their form is altered. This leads, among other things, to higher density. Therefore they have a tendency to precipitate to form deposits in water mains and other equipment. Although the treatment plants filter most of the precipitated iron and manganese before the water reaches the distribution network, a small proportion may end up in the network and accumulate inside the water mains over time. Depending on the time of year when one-way rinsing of the water mains is carried out and during sudden peak demand periods, yellowish or brownish water episodes may occur. These episodes are caused by an increase in the flow inside the water mains prompting a re-suspension of precipitated iron and manganese particles.
A sudden increase in water demand may be caused by the opening of a fire hydrant to fight a fire, by a break in a water main, by increased consumption during peak morning and evening hours or on weekends as well as in spring to water lawns and gardens and fill swimming pools.
Is yellowish or brownish water hazardous to health?
Iron and manganese are not considered hazardous to health in the concentrations normally found in nature and in the concentrations released in the distribution network.
Testing for iron and manganese is not mandatory under the Regulation respecting the quality of drinking water of the Ministry of Sustainable Development, Environment and the Fight against Climate Change (MDDELCC).
Although it is not mandatory, regular testing is carried out to determine iron and manganese concentrations so as to maintain the aesthetic quality of the water when it leaves the treatment plants before its distribution.
What should one do if the water is yellowish or brownish?
Although we do not recommend drinking water with a yellow or brown tinge mainly because of its unusual taste or odor, discoloured water may be used for other daily tasks.
However, it is best not to use discoloured water to wash white clothes as it will cause staining especially if bleach is used. Some products sold in hardware stores are designed to remove rust stains from various types of surfaces.
If a yellowish or brownish water episode occurs – and this may be limited to one home only - , the only way to remedy this situation is to flush the water out of the pipes.
The first thing to do is to let the outdoor (garden) faucet run until the water is clear. If an indoor faucet must be used, it is recommended to run the bathtub’s cold water tap or to remove the aerator if another indoor faucet is used.
What is the Town doing to improve the water’s aesthetic quality?
The one-way rinsing of the water mains across the whole municipal network is the most efficient way to remove iron and manganese deposits.
The Town carries out a one-way rinsing operation in the spring on half of the network and in the fall on the other half. If needed and whenever practicable, one-way rinsing may be carried out twice a year in certain areas.
In 2015, important changes were made to the rinsing sequences to increase efficiency. Follow-up monitoring is conducted to verify the effect of these changes and make any necessary improvements.
Does the water supply contain fluoride?
Very little if any. Fluoride is not added to the water supplied by the Town and the water drawn from our wells naturally contains very little or no fluoride.
This is the English translation of the original French text.