August 13, 2026

Why does water taste or smell bad, and how can we fix the problem?

Water can appear completely transparent, but still have an unpleasant taste and odor of chlorine, metal, earth, sulfur, or other substances. In some cases, the cause is the water's natural mineral composition, sometimes the disinfection process, organic compounds, substances present in well water, and so on.

The WHO states that drinking water should not only be safe but also acceptable to the consumer in terms of taste and odor. Furthermore, an unpleasant taste or odor does not automatically mean that the water is harmful to health – just as a good taste and odor do not guarantee water safety.

Why do the taste and odor of water change?

The organoleptic properties of water are influenced by both its natural composition and the water treatment and supply system. The cause of unpleasant taste and odor can be:

Natural minerals and gases in the water;
Chlorine or other disinfectants;
Organic compounds;
Iron and manganese;
High concentrations of dissolved salts;
Processes occurring in the water supply network or building pipes;
Specific composition of well or spring water.

The WHO also indicates that the taste and odor can be affected by the water treatment process, sediment and biofilm in the pipes, or changes in water flow.

Chlorine taste or odor

In urban centralized water supply, one of the most common causes is chlorine. Chlorine and chloramines are used for water disinfection and for controlling microorganisms in the water supply network.

According to the CDC, chlorinated water may have a different taste and odor, especially when its concentration is relatively high or when other particles are present in the water. Even when chlorine is present in drinking water at safe concentrations, consumers may still detect its taste or odor.

One of the most common methods for reducing chlorine and many taste and odor-causing organic compounds is activated carbon filtration. According to the US EPA, granular activated carbon (GAC) is used precisely for the adsorption of taste and odor-causing compounds, natural organic matter, and a range of organic contaminants.

"Rotten egg" or sulfur smell

If water has a characteristic sulfur or "rotten egg" smell, one possible cause is hydrogen sulfide - H₂S.

According to the USGS, hydrogen sulfide can be produced when groundwater comes into contact with organic matter or certain minerals. Therefore, this problem is particularly common in groundwater and well water.

If the smell only appears when using hot water, the problem may be directly related to the water heater and not to the water source. University water quality programs also note that the smell of hydrogen sulfide is sometimes particularly noticeable in hot water.

In the case of a hydrogen sulfide problem, merely installing a conventional mechanical cartridge is not enough. The EPA lists aeration among the H₂S removal technologies, while oxidation and subsequent filtration are also used depending on the concentration and chemical composition of the water.

Earthy or musty smell and taste

In surface waters, reservoirs, and sometimes centralized water supply, an earthy, musty, or mold-like smell may appear.

The USGS links this type of odor to natural organic compounds, which, for example, are produced during the decomposition of plant material.

Such problems are often associated with geosmin and 2-methylisoborneol (2-MIB) – compounds that give water an earthy or musty smell. According to the WHO, humans can detect these substances at very low concentrations, and the odor caused by their presence does not itself indicate a health risk.

The WHO notes that for reducing geosmin and MIB, conventional coagulation and mechanical filtration are not always effective, while activated carbon is one of the widely used methods for their removal.

Metallic taste

A metallic, iron, or bitter taste can often be linked to the presence of iron and manganese in the water.

As groundwater moves through rocks and soil, it naturally dissolves various minerals. According to the USGS, this is how iron and manganese can enter well water.

Iron and manganese can cause:

A metallic taste in water;
Yellowish, brownish, or reddish discoloration;
Stains on sinks, toilets, and other surfaces;
Accumulation of sediment in pipes and appliances.

Penn State's water quality program links both elements to a strong metallic taste in water and the formation of household stains.

In such cases, an activated carbon cartridge alone is not a complete solution to the problem. The removal of iron and manganese often relies on oxidation followed by passage through specialized filtration media.

Salty or unusually bitter taste

The taste of water can also be affected by the amount of dissolved salts in it.

For example, the EPA's Secondary Drinking Water Standards set a limit of 250 mg/L for chloride, 250 mg/L for sulfate, and 500 mg/L for total dissolved solids (TDS). These indicators are primarily related to the organoleptic and aesthetic properties of water, not directly to health risk thresholds.

If an unpleasant taste is caused by dissolved salts or high TDS, conventional mechanical or carbon filters cannot effectively remove them. In such cases, one applicable technology is Reverse Osmosis (RO). According to the EPA, RO can reduce many inorganic substances and dissolved salts from water.

How to find out where the problem comes from?

Before choosing a filtration system, it is important to identify the source of the problem.

If a strange taste or odor is only present at one tap, the cause may be in the local pipe, tap, or a specific appliance. If the problem is throughout the house, the probable cause becomes the incoming water or the central system.

It is also important to check whether the smell is present in both cold and hot water. In the case of hot water only, attention should also be paid to the water heater.

For well water, the CDC recommends periodic laboratory testing of the water and additional analysis whenever the water's color, taste, or odor changes.

Which filtration is used for taste and odor problems?

No single universal filter can solve all types of problems. The technology should be selected according to the specific cause.

Problem	Possible Cause	Common Treatment Method
Chlorine taste and odor	Chlorine / Disinfectant compounds	Activated carbon
Earthy or musty smell	Geosmin, 2-MIB, organic compounds	Activated carbon
"Rotten egg" smell	Hydrogen sulfide (H₂S)	Aeration / Oxidation / Appropriate filtration
Metallic taste	Iron, manganese, or pipe corrosion	Oxidation + special filtration media
Salty taste / High TDS	Dissolved salts	Reverse osmosis
Unknown or suddenly appearing smell	Water source, pipes, or possible contamination	First, water analysis, then appropriate solution

These treatment principles are based on the EPA's review of drinking water treatment technologies. The specific system configuration depends on the water composition, concentrations, consumption, and water source.

Does a bad smell mean the water is dangerous?

Not always - it's impossible to determine solely by taste and odor

The CDC explicitly states that some microorganisms and chemical substances important for health do not change the taste, odor, or appearance of water at all. On the other hand, some substances may give water a very unpleasant odor, even though at low concentrations they do not pose a significant health risk.

Therefore, if the taste or odor of water suddenly changes, is very intense, or the problem recurs constantly, especially in the case of well and spring water, it is advisable to first analyze the water and only then select the appropriate filtration technology.

Conclusion

Unpleasant taste and odor in water can be caused by completely different reasons - chlorine, organic compounds, hydrogen sulfide, iron and manganese, dissolved salts, or the water supply system itself.

That is why, when choosing a filter, it is important not only how the water smells or tastes, but also what causes this change. In some cases, quality activated carbon filtration is sufficient; in others, special iron-manganese treatment, aeration, oxidation, or a reverse osmosis system is needed.

Properly selected filtration does not cover up the symptom of the problem, but rather reduces its underlying cause.