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.

If you’ve ever turned on a tap inside your home and smelt a swimming pool like odor, you may immediately think of chlorine. Chlorine is added to municipal water supplies to disinfect the water and protect consumers against viruses, bacteria and waterborne diseases. While this is a great idea, that chlorine smell can make water unpalatable. So, here we’ll explore the chlorination process and just how much chlorine is in tap water.

Why is Chlorine Used in Drinking Water Supplies?

While treating drinking water is nothing new, the move to chlorinating water supplies was an important shift in improving public health.

Early water treatment dates back to 4,000BC, but it was primarily to correct unpleasant smells or tastes in the water. However, in the 19th century, after the understanding of germ theory, it became clear that microbes in water could be a source of disease. Early water treatment efforts involved filtering water through sand, but this failed to remove all of the disease causing microbes.

In the early 1900s, cities began to add chlorine to drinking water supplies to reduce the transmission of waterborne diseases.

Chlorination is considered to be the major way that waterborne disease outbreaks were reduced in North America and Europe. Prior to drinking water chlorination, typhoid fever had a comparable death rate to modern auto accidents. Once the adoption of chlorination became widespread, deaths from typhoid fever have been almost eliminated. This is also true of a variety of other waterborne contaminants including viruses, protozoa and bacteria.

The Downside to Chlorination

One of the drawbacks of chlorination is that the chlorine can dissipate. This means that water treatment plants need to add sufficient levels of chlorine to ensure that it remains in the water as it passes through the network of pipes to your tap.

Unfortunately, this can leave that signature “swimming pool” odor in your water supply. This may make it difficult to drink and it can alter the taste of foods prepared with the water.

Another significant drawback of chlorination is that chlorine and other disinfectant processes can create disinfection byproducts. These are formed when the disinfectant comes into contact with organic materials.

The most common disinfectant byproducts include bromate, chlorate and trihalomethanes. There are known health risks that are associated with DBPs with some considered potentially carcinogenic. Unfortunately, more research is needed to understand the full impact of DBPs.

How Much Chlorine is Safe?

While chlorine is considered vital to provide access to safe drinking water, the potential drawbacks are recognized. This means that chlorine is only considered safe for consumption at levels less than 4 milligrams per liter or 4 parts per million.

However, this is a guideline level, as some people may have a greater chlorine sensitivity. So, you may be able to notice the unpalatable odor even if your water only contains 1 part per million.

Although, at this level, it is still safe for you to drink, the odor may mean that you are reluctant to drink adequate water to prevent dehydration and may need to resort to other forms of drinking water.

How To Reduce Chlorine and DBP Levels in Your Water

Fortunately, you don’t need to deal with an unpleasant swimming pool like odor in your water supply or worry about the levels of DBPs, as there are a number of domestic water treatment options.

One of the most effective ways to eliminate chlorine from your water is the use of an activated carbon filter. Activated carbon is treated with oxygen or heat to expand its surface area. As water passes through the activated carbon media, disinfectants and their byproducts become trapped on the surface through adhesion.

Activated carbon filtration can also provide a great solution to remove other contaminants that may compromise the taste and smell of your water, including volatile organic compounds or VOCs.


Choosing a Water Treatment System

There are a variety of forms of activated carbon filtration systems, from point of use systems installed to filter the water from a specific tap or whole home systems that treat the water at the point of entry. Which you choose will depend on your preferences and requirements. If you only require treated water for drinking and preparing food, a point of use system may be sufficient. On the other hand, if you have concerns about bathing in water containing levels of contaminants or have other contaminant issues that could compromise your fixtures, pipes or water using appliances, you may prefer a point of entry system.

A home water filtration system can be an excellent way to save money on drinking water. If you don’t like the taste of your tap water, you may resort to purchasing costly bottled water. While it may seem counterintuitive, installing a water treatment system could save you a great deal of money in the long term.

If you’re feeling a little overwhelmed by the variety of treatment options, you can rely on the expertise of a professional water treatment specialist. An experienced technician can assess your water quality and measure the levels of chlorine, DBPs and other contaminants. They can then recommend treatment systems that are best suited to the characteristics of your water. This could be something like an activated carbon filtration system or something a little more comprehensive such as a reverse osmosis system, or even a combination of the two.

If you have severe water quality issues, the best option may be a RO system that can eliminate up to 99% of contaminants with an activated carbon pre filter to protect the filter membrane.


In conclusion, chlorine is a common chemical that is used by water suppliers for disinfecting the water and protecting consumers from waterborne diseases. Although chlorine can provide a massive public health benefit, it does have drawbacks, including altering the taste and smell of the water.

If you have concerns about chlorine in your water supplies, be sure to speak to your local water treatment specialist, who can check your water and guide you through the appropriate treatment methods.