Unusual colour, smell and/or taste of your water

A changed appearance of water can be an indication of a change in the quality. Often a certain change in colour, smell or taste can give an indication of what may be causing this.

It is generally recommended to test the water regularly, especially if it is used for consumption:

  • Although in most places, drinking water quality is very high when it leaves the water supplier, contamination can also happen between the water treatment facility and your tap (for example through corrosion of metal pipes, contamination in storage tanks, problems with plumbing).
  • If water comes from a private water supply or a water tank then regular tests should be standard, especially when seasons change (temperature changes, heavy rain fall & agricultural intensity can affect water quality in ground water and aquifers).


Blue or green colour:
Blue or green stains are usually a sign of increased levels copper. This could be from the water supply (ie. ground water), corrosive water and/or from copper piping. Copper can cause staining of fixtures or laundry. Copper is regulated by the UK government with a recommended maximum contamination level of 2.0mg/l ( = 2ppm). This level is low enough so that copper cannot be tasted (the taste threshold is about 5mg/l = 5ppm). Copper could become a problem if it is higher than 30mg/l ( = 30ppm) in your water, with health effects including vomiting, diarrhoea, and gastrointestinal symptoms.
To test your water for copper, click here.

Red or brown colour:
A reddish brown or rusty colour could be caused by iron (iron oxidisation & iron bacteria) or manganese. Both metals are present in the Earth’s crust, and hence can be found naturally in water sources. Both are essential trace elements and are necessary for good health. Rust (iron oxide) can temporarily give water a brown colour. Rust can be dislodged by a disturbance to a pipe, ie. a change in speed or direction of water flow. Simply run the tap until the water clears.

When iron comes in contact with chlorine (which is often used as a water disinfectant), then the oxidisation process is accelerated, causing visible particles of rusted iron in water. Iron in water can cause stains on plumbing fixtures, sinks and on laundry.
Test for iron: single kit, 12-in-One or  Watersafe Water Test Kit.

Black tint:
An odourless black tint in water is usually due to manganese. Manganese behaves like iron but it oxidises a lot slower.  It can be visible as black stains on appliances or reservoir walls.
Test for manganese: click here.

Yellow Colour:
In rare cases, when water passes through marshlands and then moves through peat soils, it can take on a yellow colour. It is more commonly found in surface water supplies or shallow wells. The yellow colour may not be pleasant but it should initially not present a health hazard.

Sometimes, a yellowish tint (sometimes brown) can also be caused by organic material in the water. These are mostly non living particles but can also include bacteria, viruses and other pathogens, in which case they can be potentially dangerous to health and water needs further tests.
To test your water for bacteria, please click here.

Should you be concerned about your water, we always recommend an overall check of your water before consumption. Do not take any risks.

Cloudy white or foamy:
Often caused by harmless tiny bubbles of air, which will clear when the water is left to stand for 5 minutes. Air can enter water in the distribution system or it may come through a faulty fitting in the property, ie. through part of the tap. It can also be caused by differences in temperature between water and the surrounding environment (most common when seasons change).

If cloudy water is still cloudy after standing for 5 minutes, then the cloudy appearance may be caused by turbidity (rather than air). Turbidity is the cloudiness of water caused by large numbers of individual particles/ solids that are usually invisible to the naked eye. This can only be removed by filtration. To test for turbidity a specialised meter is required.

Another source could be natural minerals found in water, known as hardness. The white particles are more noticeable after the water has been heated. They are flakes of limescale, calcium carbonate, which have formed in the pipework or in the kettle and will settle from top to bottom. It is generally advised to test the level of  hardness of your water to protect your appliances long term.

Oily film:
An oily film can form on the surface of boiled water. This can be an indication that galvanised iron pipes and fittings are in need of attention. This oily film has nothing to do with oil, but is a shimmering layer of very small and flat crystals of a zinc compound, which are formed and then float on the surface. As a short term measure, flush the pipe before using the water and if the problem persists, have your pipes checked. (also see paragraph ‘metallic taste’)
To test your water for zinc, click here.

Smells & Taste

Chlorine smell or taste:
Chlorine has been used for hygiene purposes for over 100 years. Chlorine in water may be present in two forms, free and combined. Free chlorine does the hard work of killing bacteria and oxidising contaminants. When you add chlorine to water, you are actually adding free chlorine. When free chlorine combines with contaminants, it becomes combined chlorine, or chloramines. In water, this form of chlorine has very little sanitising ability, and no oxidising ability. Total chlorine is the sum of both combined chlorine and free chlorine.
For free chlorine test strips click here and for total chlorine test strips click here.

Typically water companies keep the level of residual disinfectant in the form of free or combined chlorine to 0.5mg/l ( = 0.5ppm) or less. Should you notice a smell or taste of chlorine occasionally, then this could be due to maintenance work.
Treatment: If you find the smell unpleasant you could fill water in a jug, then put it in the fridge to cool down before drinking it as cold water loses the smell of chlorine. Always remember to throw away any unused water after 24 hours and clean the jug regularly.

Salty taste:
Some systems have a high mineral concentration, giving a salty or soda taste. The risk of this happening is higher when water has a lower pH and is acid. The salty taste could be due to high amounts of naturally occurring sodium, magnesium or potassium.
To test water for its salt content, we recommend a sodium chloride (salt) test. This test is also ideal to check the level of salt in water, ie. when a water softener is used (water softeners often work by adding salt to water).
To test the pH and acid-neutralising ability of water (alkalinity), use a pH & Alkalinity test.
To test the total amount of mobile charged ions, including minerals, salts or metals dissolved, use a Total Dissolved Solids (TDS).

Bitter, metallic, medicine, disinfectant or TCP taste or smell:
Chlorine in water can sometimes react with plastics and rubber in plumbing or kitchen appliances. This can make the water taste bitter, metallic, like medicine or disinfectant or TCP. Causes are unsuitable or degraded tap washers, rubber tap expensions, or sealing rings in kettles – even at very low concentrations these phenolic chemicals react with chlorine in water to create chlorophenols & TCP. Apparently this is not harmful, although the taste and odour is noticable even at low levels.

Potential causes:

  • the flexible cold water feed pipe on washing machines or dishwashers – to check, turn off the water supply to the appliance using the service valve at the point where the hose connects to the mains supply. Then run the tap and to see if the TCP smell disappears after a short while. If this is the case then the flexible hose is likely to be the source of the problem. Install a one-way check valve fitted to the connector to prevent backflow.
  • dissolving material from within the kettle, particularly when new. Follow manufacturers guidelines when using a kettle for the first time.

Metallic taste:
Often, metallic taste is caused by metals from copper, iron or galvanised pipes. Corroding copper or zinc pipes may produce metallic tastes.  Zinc imparts an undesirable astringent taste to water. Tests indicate that 5% of the population could distinguish between zinc-free water and water containing zinc at a level of 4mg/l ( = 4ppm) (as zinc sulphate). Water containing zinc at concentrations in the range 3–5mg/l ( = 3-5ppm) also tends to appear opalescent and develops a greasy film when boiled. (also see paragraph ‘oily film’)
Click here for a water copper test kit or a zinc test kit.

A metallic taste may also be present with excess iron. If iron bacteria is present, gelatinous sludge may be present on plumbing fixtures or cause pipe encrustation. (also see paragraph ‘Red or brown colour’)
To test for iron: single kit, 12-in-One or Watersafe Water Test Kit.

Rotten egg odour:
This is usually the result of decaying organic deposits. Bacteria growing in the sink drain or hot water heater may cause odour. As water flows through these areas, hydrogen sulphide gas could be picked up, and the gas may be released into the air later. Hydrogen sulfide gas produces the rotten egg odour, can be corrosive to plumbing at high levels, and can tarnish silver rapidly. As little as 0.5mg/l ( = 0.5ppm) can be tasted in drinking water.
To test for hydrogen sulphide using a single kit click here or use our 12-in-One test kit.

Treatment: If caused by sulfate-reducing bacteria found in water that feeds on sulfates, then treatment is to disinfect all plumbing with household bleach and pre-treat the water supply with chlorination to eliminate the bacteria, then to remove the chlorine smells, you’d use an activated carbon filter. If the cause is from dissolved hydrogen sulphides (H2S), it is best to consult a water quality professional for assistance with this issue.

Musty or earthy tastes or smells:
These smells are usually a result of harmless organic matter. Bacteria can grow in the sink drain or on grease or fibre washers used in the plumbing, especially if the pipework is warm and rarely has water flowing through it. Even very low amounts can cause unpleasant odours.
To test water for bacteria click here. If the problem persists then cleaning and disinfecting the plumbing system may be necessary.

Ammonia smell:
NH3, ammonia gas, is extremely soluble in water. It is the natural product of decay of organic nitrogen compounds. Although it is widely used and common in our environment, ammonia can be both hazardous and caustic. Ammonia gets into water supplies most frequently as runoff in agricultural areas where it is applied as fertiliser and it easily finds its way into underground aquifers from animal feedlot runoff. Ammonia itself is not often found in well water because bacteria in the soil tend to convert it to nitrates. Ammonia can be very corrosive to some copper plumbing systems. Ammonia is not regulated by current drinking water standards. Ammonia is toxic to fish and to dialysis patients. Its toxicity varies with the pH of the water.
To test water for ammonia click here.

Treatments: The natural zeolite clinoptilolite, also regenerated with salt, is also an effective ammonia treatment. For drinking water, distillation is an effective treatment.


Some elements in water can not be identified by colour, smell or taste. They may however, still be harmful after short or longterm exposure. These can include Aluminium, Arsenic, Bacteria, Legionella, Lead and Heavy Metals. It is important to test water regularly ensuring that it is safe.

Should you be concerned about your water, because of a changed appearance, then we always recommend an overall check of your water before consumption. Do not take any risks.

For more detailed information about each of the elements listed above, please also visit our page Most common elements found in water.


1. Always use freshly drawn cold water from the mains tap (usually the kitchen tap) for drinking or cooking.

2. Do not use hot water or water from your bathroom taps for drinking and cooking because it usually is not as fresh or as safe as water directly from the mains.

3. When water has not been used in the house for several hours (or days, ie. after a holiday), fill a washing up bowl full of water first. This way you avoid drinking water, which has been sitting in your pipes for a long time. You don’t need to waste any water, simply use it to water your houseplants or the garden.

4. If you notice a particularly bad or strong smell or taste which makes your tap water unpalatable, or you notice a smell or taste for the first time, which does not go away in a short time, then you should contact your water company immediately. Do not take any risks.

5. When a problem occurs, it is always a good idea to speak to a neighbour, to see if they have the same problem or whether it is only specific to your house. Internal storage tanks or piping systems can also be causes for problems. It is also useful to check whether the problem arises from the mains-fed cold tap (normally the kitchen tap) or via the storage system (check the bathroom tap).

6. Always check with your water supplier or a registered plumber if you have any serious concerns about the quality of your drinking water.

7. Tap hygiene – keep your taps always clean and make sure that food does not come in contact with your taps. Taps – if not cleaned properly – can become a breeding ground for bacteria and hence contaminate your water.

8. Fit non-return valves to hose pipes, dishwashers and washing machines so that water in flexible hoses cannot return into the mains supply.

9. Check that your water tank is in a good condition and covered with a close-fitting lid to avoid anything falling or getting in.


Most countries have standards or guidelines regarding the maximum contaminant levels in drinking water. Globally, there is an overall agreement on the science behind the setting of these standards. Mostly, they are guided by worldwide research and the standards set by the World Health Organisation. The UK government has also published a set of water quality standards, which are guided by the European Union together with national standards. The UK’s maximum contamination levels* have been used in the illustrations above. Please check your local guidelines.

(*More information about UK maximum contamination levels for other parameters, can be found on this website:
http://dwi.defra.gov.uk/consumers/advice-leaflets/standards.pdf , this is part of the website from the British Drinking Water Inspectorate (DWI/ DEFRA).

Further Free Resources:

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Disclaimer: Only opinions based upon our own personal experience or information detailed in academic journals or other publications is cited. This has been done exclusively for anyone who is interested in this subject but is not intended to replace proper analysis. We cannot accept responsibility and liability of any kind which may result from the application of this information. We always recommend to consult an expert to discuss any test results or get a full recommendation on the specific subject and specific to your situation by an expert.

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There are strict standards for the quality of drinking water within Europe mainly laid down in the EU Drinking Water Directive (98/83/EC). These are based on advice from the World Health Organisation (WHO).