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Why is Chlorine used to treat tap water?

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What is chlorine?

You know the name and you know the smell, but how much do you actually know about this chemical element? Before we can dive into the effects of chlorine on your water, home, and body, we need to understand what it actually is.

Chlorine (Cl, atomic number 17) is a fairly common element, typically found combined with other elements in compounds like sodium chloride (rock salt). Outside of these natural compounds, however, chlorine can be significantly less friendly.

Chlorine gas is a toxic substance that attacks the respiratory system, eyes, and skin. It is detectable by smell at 3 parts per million (ppm). Coughing and vomiting may occur at 30 ppm, with lung damage occurring at 60 ppm. About 1000 ppm can be fatal after just a few deep breaths of the gas. Scary stuff!

It may therefore be a bit of a shock to hear that chlorine is one of the most widely used disinfectants in the world, found in homes, industrial cleaning products, and health care facilities. It is used to disinfect swimming pools and spas, clean equipment in restaurants, and even sterilise feeding bottles for babies.

It is also used as both a disinfectant and an oxident in various forms of sanitation like water and wastewater treatment processes. With sanitation being a big part of our lives over the last couple of years, it’s just as important to think about what we’re sanitising with.

Chlorine in water

Why is it added to drinking water?

Simply put, chlorine is effective in killing many types of bacteria, viruses, and parasites. Some of these include Escherichia coli, listeria, salmonella, and other micro-organisms. Since chlorine has been added to water supplies, there has been a drastic reduction in water-borne infections like cholera, typhoid fever and dysentery. It is simple to use, effective in killing bacteria, and most importantly inexpensive. This makes it the go-to for treating large amounts of water.

The inexpensive factor is one of the key reasons it is still used in water treatment today. However, with advancements in technology creating more viable alternatives, many countries have sought ways to move away from chlorination.

The best example of this is the Netherlands. Up until the mid-1970s, like the majority of countries around the world, they relied on chlorine to treat water. After discovering that it produced trihalomethanes (more on these later), though, the country began dedicating time and resources to reducing its reliance on chlorine. In 2005, the Netherlands successfully moved away from chlorinated water treatment solutions and implemented a four-point approach:

  1. Use the best available water sources
  2. Find alternatives to chlorine
  3. Prevent contamination
  4. Constant monitoring of the water quality

The Dutch model owes much of its success to the use of physical filtration. A system of sediment filtration in combination with UV disinfection completely eliminates the need for bleaching their water with chlorination.

So why doesn’t everyone switch to the Dutch model? The main problem is that the Netherlands is the most densely populated country in Europe, so replacing the infrastructure required to achieve this model was financially feasible. In Australia’s case, the combination of a sparse population and much higher variance in water sources makes this model unrealistic and impractical.

Levels in Australia

Now that we understand the reasons for using such a harsh chemical to treat water, it is important to look at just how much is used. The levels found in Australian tap water are regulated by the Australian Drinking Water Guidelines. According to the guidelines, the maximum level of chlorine that may flow through your taps is 5mg/L. This number may come as a surprise to pool owners, as most pool testing kits recommend keeping chlorine levels below 3mg/L for safe swimming.

While this is the maximum level listed in the official guidelines, the actual levels you would find in your home would be much lower. Throughout Australia, most homes will see somewhere between 0.5 – 1.5mg/L. In some areas, however, a kitchen tap might produce numbers upwards of that 3.0mg/L safe swimming level. You wouldn’t drink a glass of water from your swimming pool, so why ingest those levels from your tap?

Problems with chlorination

In drinking water, the most obvious problem with chlorine is that it leaves an unpleasant taste and can often have a distinct smell. However, these are just the immediately noticeable problems; the real issue is often not the chlorine itself, but what happens when it reacts with other materials.

According to a Belgian study that was released in 2003, certain irritants called trichloramines are released any time chlorinated water reacts with organic materials. These trichloramines are believed to initiate a biological process that effectively destroys the cellular barriers surrounding the lungs.

“Cancer risk among people drinking chlorinated water is 93% higher than among those whose water does not contain chlorine.”

According to the U.S. Council Of Environmental Quality

Apart from ingestion through drinking water, another major source of exposure is your shower. The evaporated chemical is breathed in through the steam, and a small amount is even absorbed into your skin. This can make your hair and skin feel dry after showering, as your immune system may identify the chlorine as a “foreign invader” like bacteria or a virus and become inflamed and irritated.

You may never have experienced unusually dry skin after a shower or bath, but observations of individuals with more sensitive skin suggest that chlorinated water may play a role in the development or worsening of atopic dermatitis (the most common form of eczema). A study from the American National Library of Medicine found that the water-holding capacity of the upper layer of the skin in patients with eczema was more sensitive to free residual chlorine than in patients without eczema.

Although the effects of chlorination may not be immediately seen as with those with eczema, with the sheer amount of the stuff we expose ourselves to every day, we have no way of knowing the long-term effects chlorinated water might be having on our bodies.

“When chlorine enters the body as a result of breathing, swallowing, or skin contact, it reacts with water to produce acids. The acids are corrosive and damage cells in the body on contact.”

New York State Department of Health

In the long, run showering and bathing in chlorinated water is an even more significant source of exposure than just drinking it. Since it tends to dehydrate the skin, many people find that simply removing chlorine from their bathing water can have a beneficial effect on their overall wellness.

Although a great deal of research has already taken place, until we know more about how chlorinated water affects our health, the safest option is to keep exposure to a minimum.

How do I dechlorinate my water?

Fully abandoning chlorination at the source probably remains unrealistic for Australia as a whole, but once the large-scale disinfectant has done its job, it becomes much easier for individual homes to remove it. Whole home filtration has emerged as a cost-effective and practical method of removing harmful chemicals before the water even enters your home. This means cleaner, healthier water – not just for drinking, but for your shower and bath as well.

Our Complete Home Filtration systems are fitted with carbon filtration, which adsorbs chemicals and pollutants without leaving any negative effects on your water supply.

These filters remove 98.5% of the chlorine in your water, returning it to its original taste, odour and organic compound delivering clean, filtered water to every outlet in your home.


Australian Drinking Water Guidelines:

Department of Health WA:

Water treatment alternatives:

National Library of Medicine:

Facts about Chlorine: