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THMs & VOCs – What’s In My Water?

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Pure water, despite being essential for all sorts of biological, chemical and mechanical processes, is surprisingly difficult to find. From chemical fumes contaminating clouds to bacteria growing in natural lakes, the water cycle provides a lot of opportunities for interference. Even in countries blessed with nearly universal access to safe drinking water, the average household tap is providing a lot more than just H2O.

Artificial Additives & Accidental Accumulations

The impurities and contaminants in household water supplies can be divided into three categories:

1. Environmental Contaminants

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These are the particles that are already in the water when it begins its journey to your home. The types of environmental contaminants present in your water will vary depending on where you live and where your water comes from; groundwater, for example, will typically have quite high mineral levels, while water from a lake or surface reservoir will be more susceptible to airborne contaminants.

Environmental particles can be natural substances sediments and bacteria, or man-made pollutants like pesticides and PFAS compounds.

2. Treatments

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Municipal or state-provided water goes through a treatment process to make sure it’s safe for human consumption. Treatments are chemicals and substances that have been deliberately added as part of this process to neutralise bacteria and improve the quality of the water being supplied to our homes.

Chlorine is one of the most common water treatment chemicals and will be present at various concentrations in most town water supplies across Australia. Depending on your location and water provider, your water may also contain substances like fluoride and chloramine.

3. By-products

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These are the unintentional contaminants and impurities produced by the water treatment and supply system. Many of them are disinfection by-products (DPBs) created when chemicals like chlorine and chloramine react with bacteria or other organic particles in the water.

By-products can also be inorganic substances like metal particles collected from aging pipes and infrastructure as the water travels from the treatment plant to your home.


The Australian Drinking Water Guidelines outline official treatment methods and provide restrictions on various chemicals and contaminants that may be present in our water, limiting them to specific allowable levels. The guidelines and treatments do an excellent job of neutralising waterborne diseases and bacteria, but when it comes to regulating harmful chemicals, Australia’s laws are surprisingly lax.

Contaminants that fit into the by-product category are seen as necessary sacrifices to keep the treatment process running efficiently and effectively. DPBs, while certainly not as devastating as an outbreak of cholera or typhoid, are still worth careful consideration.

What’s the Deal with Disinfection By-Products?

The most common DPBs in Australian drinking water are trihalomethanes (THMs). These compounds are primarily produced by chlorine reacting with organic matter, but may also be present in water treated with chloramine.

THMs are classified as volatile organic compounds (VOCs), having a high vapour pressure (they evaporate easily) and low water solubility (they remain intact in water). VOCs are typically fumes produced by things like paint strippers, pesticides and chemical cleaners, but they can also come from disinfectants in your water and be released into the air as steam or water vapour.

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While THMs can be formed with any halogen chemical (elements from the 17th column of the periodic table), the compounds present in drinking water are typically made with either chlorine or bromine. Chlorine is, of course, added deliberately during treatment, but bromine is the most likely of all the halogens to appear as an environmental contaminant.

The most well-known of these compounds is chloroform, used by many an action hero or fictional kidnapper to instantly render another character unconscious. This rapid reaction is a dramatic exaggeration, but while a handkerchief soaked in tap water won’t knock anyone out, trihalomethanes certainly don’t do our bodies any good.

Chloroform, bromoform and the other more syllable-heavy trihalomethane compounds are carcinogens with links to bladder and colon cancer, even at low concentrations. Higher exposure levels can lead to issues with reproductive health and cause kidney, liver and nervous system damage.


Because THMs are a known by-product of chlorine disinfection, Australia’s water regulations accept that these compounds will be present in our drinking water and set an upper limit of 250 micrograms (0.00025 of a millilitre) per litre. However, even this minute amount is significantly above the standards in other countries; Europe lists the maximum safe THM level at just 100 micrograms, and some US states like Delaware have set the limit as low as 80 micrograms. Australia’s tap water can legally contain more than three times the safe limit of THMs identified in other developed countries.

What Can I Do About It?

Fortunately, THMs can be removed from your drinking water relatively easily. Most charcoal or activated carbon filters are rated for THM removal, and the high vapour pressure of VOCs means it only takes about five minutes of boiling to completely evaporate any THM compounds that are present in your tap water.

However, there are plenty of ways THMs can bypass your kettle or filter jug to get into your home and body. Studies have found that we absorb more THMs through our skin and lungs during water-adjacent activities than we get from drinking contaminated water.

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A series of tests in 2005 found that showering, bathing and washing dishes by hand all led to higher concentrations of THMs in the subjects’ blood than drinking water, with activities involving hot water often showing twice as much exposure/absorption as cold water. Evaporating the compounds may separate them from the water, but it certainly doesn’t make them disappear – if anything, it makes it easier for them to enter our bodies.

The answer, therefore, is to remove them from your water with an effective filtration method as early as possible. Whole-home water filters with activated carbon cartridges remove contaminants before they can enter your home, and systems from Complete Home Filtration can reliably remove 98.5% of THMs and other VOCs (along with any chlorine still present in your water, preventing the creation of more DPBs within your own pipes).

Reverse osmosis (RO) is also an option for guaranteeing the removal of THMs – and just about everything else – from your drinking water. While most tap filters have cartridges between 10 and 0.5 microns, RO systems force the water through a semi-permeable membrane with pores as small as 0.0005 microns, stripping out the vast majority of impurities. Complete Home Filtration’s RO systems also come with remineraliser cartridges to restore trace amounts of vital minerals so that you’re not sacrificing any health benefits for the sake of avoiding unwanted chemicals.

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If all these acronyms have got you thinking about your home’s H2O, send us a message below or fill out our contact form to organise a free water test and/or receive a personalised quote for your own Complete Home Filtration system.