Among the various methods used to disinfect tap water, chlorine has held a leading position for many decades. Its effectiveness, low cost and ease of use have made it an essential tool for large-scale water treatment.
However, the use of chlorine also raises important questions. Concerns exist regarding the formation of disinfection by-products that may be harmful to public health, as well as the emergence of resistant micro-organisms.
In this article, we explore how chlorine affects the taste and smell of drinking water.
Why Is Chlorine Found in Drinking Water?
Chlorine is present in drinking water for one essential reason: disinfection. It is a powerful disinfectant that removes harmful micro-organisms such as bacteria, viruses and protozoa, which can cause serious illness.
What Is Chlorinated Water Made Of?
The chlorine found in drinking water is not pure chlorine, but a chlorine-derived compound. It dissolves easily in water and combines readily with other particles, especially sodium, to form sodium chloride (table salt). Most chlorine is therefore naturally found in seawater and soils in the form of mineral salts.
There are two main ways chlorine is added to drinking water:
- Sodium hypochlorite (NaClO): the most common form used for water disinfection, also known as bleach solution.
- Hypochlorous acid (HOCl): the active form of chlorine responsible for disinfection. Sodium hypochlorite dissolves in water to form hypochlorous acid, with the proportion depending on water pH.
Technically, chlorinated water is produced by dissolving a chlorine-based compound in water. This process then creates hypochlorous acid, which acts as the disinfectant.
How Does Chlorine Remove Bacteria and Viruses?
The effectiveness of chlorine in tap water is based on the following mechanisms:
- Attacking cell walls: as an oxidising agent, chlorine disrupts the structure of cell membranes, causing rupture and cell death.
- Denaturing essential proteins: chlorine alters proteins needed for microbial survival and reproduction.
- Interrupting metabolic processes: chlorination affects the cell’s ability to produce energy and synthesise vital components.
- Oxidising nucleic acids (DNA and RNA): chlorine damages genetic material, preventing replication.
The presence of organic matter in water can reduce chlorine’s effectiveness by consuming it or forming less active chlorinated compounds. Effective disinfection therefore requires reasonably clean water.
Its effectiveness also depends on:
- sufficient contact time,
- a slightly acidic environment (pH 6.5–7.5),
- warmer temperatures,
- adequate chlorine concentration.
Advantages of Chlorine Compared with Other Methods
Effective Against Pathogens
Chlorine removes a broad range of micro-organisms, including bacteria, viruses and protozoa responsible for illnesses such as dysentery, cholera and typhoid. This differs from simple filtration, which mainly removes suspended particles rather than destroying all micro-organisms.
Its rapid action also allows quick decontamination, which is particularly valuable in emergency situations.
Unlike some disinfectants such as ultraviolet light, chlorination has a residual effect. In other words, it continues killing micro-organisms after application, providing lasting protection.
Easy to Use
The chlorination process is relatively simple to implement compared with other methods such as ozone and does not require complex infrastructure.
This makes it especially suitable for rural communities and emergency settings where advanced treatment systems may be difficult to deploy.
Good Value for Money
The low cost of chlorine makes it possible to treat large quantities of water affordably, helping improve public health on a broad scale.
How Does Chlorine Affect the Taste and Smell of Drinking Water?
Chlorine has a distinctive bitter, metallic taste that can be detected even at low concentrations. This can mask the subtle natural flavours present in water, such as freshness or mineral character.
Chlorine can also react with organic matter in water to create volatile chlorinated compounds. These compounds may contribute to an unpleasant smell often associated with tap water.
This is why some people describe chlorinated water as having a swimming-pool-like odour or a chemical aftertaste.
What Are the Possible Health Concerns Linked to Chlorine in Water?
Despite its many benefits, chlorine does not remove every contaminant. Some protozoan parasites may survive, and chlorination does not eliminate chemical pollutants or heavy metals.
Long-term use of chlorine may also lead to the formation of potentially harmful by-products.
Possible concerns include:
- Cancer: chlorinated by-products such as trihalomethanes (THMs) may be linked to a higher risk of certain cancers, including bladder cancer.
- Heart disease: oxidative stress linked to by-products may contribute to cardiovascular risks.
- Premature ageing: chlorine-related oxidative damage may affect cells and arteries.
It is therefore important to understand chlorine’s limits and combine it with other treatment methods when needed.
Alternatives to Chlorine for Water Treatment
Boiling
Boiling water remains a common way to make it safer to drink. Heat kills most harmful bacteria, viruses and parasites. However, boiling does not remove heavy metals, nitrates or many chemical contaminants.
Ozone Disinfection
Ozone is highly effective, acts quickly and leaves no residual taste. It can also improve odour and colour. However, it is unstable and usually requires continuous production.
Ultraviolet (UV) Treatment
UV treatment disinfects water without affecting taste or smell. It damages microbial DNA, preventing reproduction. However, cloudy water can reduce effectiveness, and additional treatment may still be needed.
Reverse Osmosis
Reverse osmosis uses pressure and a semi-permeable membrane to remove salts, micro-organisms and many contaminants. It is highly effective but more expensive and complex to install.
Microfiltration
Microfiltration removes larger particles through fine pores. Some systems include activated carbon, which improves taste and smell by reducing residues such as pesticides. However, it may require additional disinfection.
How to Reduce Exposure to Chlorine
Use Home Water Filtration
Home water filtration systems can provide healthier, better-tasting water and reduce chlorine exposure.
Common options include:
- tap-mounted filters,
- under-sink filters,
- filters for coffee machines,
- gravity-fed filtration systems.
At Weeplow, our gravity-fed systems contain activated carbon, which adsorbs a wide range of contaminants including chlorine, heavy metals and PFAS.
Daily Habits to Reduce Chlorine Intake
- Replace filters regularly according to the manufacturer’s guidance.
- If no filter is available, boil tap water for one minute to reduce chlorine gas (though not other contaminants).
- Use filtered water for drinks and cooking, especially pasta, rice and vegetables.
- Use a glass or reusable bottle filled with filtered water instead of drinking directly from the tap.
Protect Yourself with Better Habits
Chlorine remains a practical and effective disinfectant that protects drinking water from harmful micro-organisms. However, it can also affect taste, smell and raise broader concerns.
While alternatives exist, they are often more expensive or harder to implement.
That is why reducing exposure through good daily habits and effective filtration is often the most practical solution. Browse our shop to find the gravity-fed water filtration system best suited to your needs.
