Strange taste or smell to my water

Chlorine

What causes a chlorine taste?
Chlorine is added to drinking water during the final stages of treatment to kill any harmful germs that may be present. A small amount of chlorine remains in the water as it makes its way to customers’ taps in order to maintain its wholesomeness and the chlorine levels found in drinking water are not harmful. Chlorine levels in drinking water are kept well within the recommended limits of 5mg/l and chlorine levels added at the water at treatment works and service reservoirs are closely monitored 24 hours a day.

Chlorine concentrations can vary slightly throughout the day as increased demand for water will result in water travelling faster through the system. Changes in water temperature can also affect chlorine concentrations, with higher levels experienced in the winter. Customers who live near a water treatment works or an automatic chlorine booster station will receive drinking water with slightly higher chlorine levels than those living further down the system as chlorine levels decline the further water travels through the water mains. Some people are more sensitive to the taste and smell of chlorine than others.

Useful tips:

• Filling a jug with water, covering it and allowing it to stand in the fridge until required for use can reduce the chlorinous taste. Any water not used after 24 hours should be discarded.
• A chlorinous or metallic taste in hot drinks, especially tea, is unlikely to be caused by the presence of chlorine and is most likely associated with internal plumbing materials. If this is the case, you should contact your plumber for advice.

We recommend the use of plumbers listed on WaterSafe – the national register for qualified and competent installers. You can search for one here.

Chemical or medicinal

What causes a chemical taste or smell?
Customers occasionally contact us to report that the water from their tap has an unpleasant taste, often described as TCP, medicinal, metallic or bitter. Sometimes this taste occurs only in boiled drinks, or when a glass of water has stood for a period of time.

These tastes and odours can be caused by the reaction between the small but essential amounts of chlorine present in tap water and the plastic or rubber constituents found in common household appliances such as some kettles, tap washers, and the hoses connecting dishwashers and washing machines to the mains water supply. If you notice the taste or smell only in hot drinks, it may be due to the seals in your kettle or new appliance.

Useful tips:

• To confirm whether the dishwasher or washing machine hose is the cause, isolate the hose and taste the water again. If this solves the taste problem, fit a non-return valve on the end of the hose where it connects to the pipework. A plumber should be able to help with this.
• To confirm whether the kettle is the issue, try making a hot drink with water boiled in a saucepan and compare the taste with one made from the kettle.  

We recommend the use of plumbers listed on WaterSafe – the national register for qualified and competent installers. You can search for one here.

Bitter or metallic

What causes a bitter metallic taste or smell?
A metallic or bitter taste can be caused by an increase in commonly found metals in the domestic plumbing system such as copper, iron, or galvanised pipes. It can be more noticeable in properties that have a large quantity of internal pipework which may lead to water sitting in the pipework for a longer amount of time. This taste and smell can also be more noticeable when the water has been warmed.

Occasionally glasses or cups that have been through a dishwasher may retain traces of detergents which can also lead to a bitter taste.

Useful tips:

• If water has been standing for several hours in the pipe, fill a washing up bowl with water and draw fresh water through the pipe. The water in the bowl can be used for watering plants and need not be wasted.
• Try rinsing the glass or cup with tap water and see whether the taste persists. If so, adjust the settings on your dishwasher and use no more than the recommended amount of detergent and rinse-aid.

Earthy or musty

What causes an earthy or musty taste or smell?
An earthy or musty odour and taste can sometimes be caused by stagnant water in the internal plumbing system. Long sections of internal pipework that are used infrequently (also known as dead legs) can also lead to water stagnation over time, and can contribute to a earthy or musty taste to the water.

Some customers may notice a musty or earthy taste and odour to their mains water supply, especially in warmer weather. This may be due to a naturally occurring substance that can be present in some reservoirs. The substance appears in environmental waters and is produced by natural environmental activity in the reservoir which can increase during hot summers when water temperatures rise. It is naturally occurring and is not harmful to health, but can give rise to a musty-earthy type odour at very low concentrations. We give the water additional treatment to help deal with the substance, which cannot be removed through our usual treatment process at our water treatment works.

Useful tips:

• If water has been standing for several hours in the pipe, fill a washing up bowl with water and draw fresh water through the pipe. The water in the bowl can be used for watering plants and need not be wasted.
• Sometimes it may be a earthy or musty smell inside a property that is affecting our sense of taste and smell of the water. We would recommend filling up a glass of water and walking outside the property, and then checking to see if the smell and taste is still noticeable.
• To find out if there’s a known earthy or musty detection in the network in your area, please check the ‘In Your Area’ section of the website.
• If the issue is due to the internal plumbing in the property, you should contact a plumber for help and advice.

We recommend the use of plumbers listed on WaterSafe – the national register for qualified and competent installers. You can search for one here.

Fuel or diesel

What causes a fuel smell or taste?
In certain instances, customers may accidentally spill heating oil or fuel on driveways and gardens and if there is a plastic service pipe located in this area, the fuel/oil can adversely affect the water in the service pipe. It may take some time for the oil or fuel to travel though the soil to reach the service pipe.

If you detect a fuel taste or smell on your water supply, get in touch with us using Welsh Water’s customer operational helpline. A Welsh Water inspector and sampler will visit your property to investigate the cause of the taste or smell.

Useful tips:

• Sometimes the smell of fuel or oil inside a property can affect our sense of taste and smell on the water. We would recommend filling up a glass of water and walking outside the property, and then checking to see if the smell and taste is still noticeable. If so, get in touch with us using our helpline number.

Sewage

What causes a sewage smell or taste?
If you detect a sewage taste or smell on your water supply, customers should contact Welsh Water’s customer operational helpline as soon as you notice it. A Welsh Water inspector and sampler will visit your property to investigate the cause of the taste or smell.

Useful tips:

• If you fill a glass with water and take it into another room and the sewage smell is no longer present then the issue is likely to be with the sink or the drains, which should be cleaned or unblocked.
• If the smell is still present on the glass of water when you take it away from the sink this could indicate an issue with your plumbing, and you should contact us via our operational helpline number.