Bleach or disinfectant

If there is a faint taste or smell of bleach or disinfectant from your drinking water, this is most likely due to chlorine.


Chlorine plays an important role in protecting public health by killing harmful bacteria in our drinking water. This is a necessary disinfectant used worldwide across the water industry to help maintain a safe drinking water supply. Almost all water supplies have added chlorine and, as a result, the water from these supplies will have a slight chlorinous taste and smell. This is not harmful to your health. If the taste or smell becomes significantly more noticeable than what you are used to, please contact us on 1850 278 278 and we will ensure it is promptly investigated. Please note that the rates charged for 1850 numbers may vary across different service providers. Calls from mobiles may be more expensive.

Health implications

The level of chlorine in your water is carefully monitored and controlled to ensure it is maintained at levels that are not harmful to your health. Sometimes operational changes during the treatment process may result in a slight increase in chlorine levels in the supply and this may result in a change of the taste and smell of the water.

What to do if your water smells of chlorine

If the smell or taste of Chlorine is stronger than normal, you should fill a jug with tap water, cover it and store in the fridge, preferably over night. This should reduce the smell and/or taste of Chlorine.

Earthy or musty

Sometimes earthy tastes can develop in drinking water. This can be caused by one or more of the following.

Stale water

Drinking Water that has been sitting in the pipe for a relatively long time can develop a stale or earthy taste /smell. This is most likely to occur in long service connections or in buildings that have drinking water storage tanks (e.g. apartment blocks).


There may be bacteria in your plumbing system causing the earthy or musty smell. If you suspect that this is the case (e.g. if your neighbours do not have the same issue) you should consult your local plumber for assistance.

Source water

In some cases, an earthy taste can originate from the source water. Growth of algae in the area where the water is abstracted may result in an earthy or musty taste / smell in your drinking water. This typically occurs in lakes or impounding reservoirs. The most common naturally occurring chemicals associated with such taste and smell issues are Geosmin and 2-Methylisoborneol (MIB). Further information on these two chemicals are provided below.

Health implications

While the taste and smell can be unpleasant, drinking water with an earthy or musty taste is typically harmless. However, if your water develops an unexpected earthy or musty taste, you should contact Irish Water and we will immediately investigate the issue.

What to do if your water smells earthy or musty

You may wish to speak with your neighbours to see if they are experiencing similar earthy taste / smell issues. Running the cold water tap in your kitchen sink for a few minutes may clear any stagnant water in your system. If the taste / smell does not improve after running the tap, you should contact Irish Water and we will immediately investigate the issue.

If you suspect that the source of the problem is within your plumbing system you should consult your local plumber for assistance.

  • MIB is an abbreviation for 2-Methylisoborneol. Both MIB and Geosmin are a naturally occurring organic substance produced by both algae and filamentous bacteria found in lakes, rivers, streams and reservoirs. 
  • Sometimes the presence of MIB or Geosmin in water can cause and earthy or musty taste or smell.
  • The presence of MIB in drinking water, while not harmful to your health, even at tiny levels can give it an earthy, musty taste and odour.
  • While the taste and odour effects from both MIB and Geosmin can be unpleasant for some people, they are not toxic and the water remains safe to drink. Irish Water undertakes regular monitoring of our water supplies to verify there are no harmful bacteria or other pathogens in the water.
  • Conventional water treatment processes do not remove MIB or Geosmin. The main objective of water treatment is to ensure your drinking water is free from harmful bacteria or parasites that could cause illness to you or your family. The drinking water we produce is safe to drink and regularly tested to ensure all microbiological and chemical parameters are compliant with the drinking water regulations.
  • Seasonal increases in naturally occurring algae or release of MIB and/or Geosmin from bacteria in water sources can cause a rise in these chemicals above the taste and odour threshold for some people. It is typically seasonal in nature and limited in duration.

Concerned about the quality of your drinking water? Contact us on 1850 278 278. Lines open 24 hours a day, 7 days a week. Please note that the rates charged for 1850 numbers may vary across different service providers. Calls from mobiles may be more expensive.

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