By Mark Nelson President Nelson Water:

With more than 30 years’ experience in the residential and commercial water treatment space, Mark Nelson is a Class 1 Drinking-Water Operator and a CBWA (Canadian Bottled Water Association) Certified Plant Operator. As founder and president of Nelson Water in Ottawa, Mark focuses on dealing with challenging water treatment system designs for problem water. He also heads the largest water bottling plant in the city of Ottawa with a delivery network throughout the Valley.

Over the years chlorine has be the default chemical used to disinfect city drinking water. This changed during the last decade when many cities moved over to using chloramine as their residual disinfectant of choice. This was done because chloramine is a more stable molecule that will persist longer in water than chlorine. This stability makes chloramine harder to remove from the water, and specialized water treatment will be needed. For this reason, we have compiled a list of the top 5 Canadian cities by population and whether they use chlorine or chloramine to disinfect water.

Cities Using Chlorine

  1. Montreal, QC
  2. Calgary, AB
  3. Winnipeg, MB
  4. Vancouver, BC
  5. Brampton, ON

Cities Using Chloramine

  1. Toronto, ON
  2. Ottawa, ON
  3. Edmonton, AB
  4. Mississauga, ON
  5. Markham, ON

Chlorine vs. Chloramine

When your city disinfects drinking water, it’s a two part process.

The first stage is known as primary disinfection, and this is where pathogenic organisms, such as viruses, bacteria, and cysts are destroyed. The next stage is to treat the water with residual disinfectant further as it travels through the water pipes to reach our homes. As you can see above, the vast majority of water treatment in Canada uses free chlorine, which is an oxidizer that destroys the organism’s tissues to kill them.

When we examine the differences between chlorine and chloramine, we are usually discussing the choice of residual disinfectant. Increasingly, we are seeing the adoption of chloramine for this purpose because it will not naturally dissipate in the air or aggressively react to surfaces. In essence, the chloramine will last longer and will not cause as much damage to pipes. A more persistent chemical disinfectant will be more persistent and provide better disinfection for people.

The Problem with Chloramine

The very properties that make chloramine attractive as a water disinfectant make it harder to remove for homeowners. Chloramine is a very stable molecule compared to chlorine and if you want to remove it a water treatment system using activated carbon will be required. This will also remove chlorine, so if your city isn’t listed above, this type of water treatment method will also remove that unpleasant “swimming pool” taste.

If you have concerns about your water supply, you should speak to a water treatment specialist. A fully CWQA certified professional can not only assess your water quality, but guide you through the available options that are best suited to your specific requirements.