Colour
Guidelines
Unit of measurement
mg/l Pt/Co
World Health Organisation Standards (1993)
Acceptable to the consumer
Standards for private water supplies in England (2016)
20
Standards for private water supplies in Scotland (2006)
20
Standards for private water supplies in Wales (2017)
20
European Union Drinking Water Directive (1998)
Not mentioned

Colour

When most of us picture water it is likely that we visualise a calm blue lake or a turbulent navy ocean when in fact, we expect our drinking water to be clear and colourless. If your drinking water has a coloured hue to it, this could indicate that there is an issue with your water supply and/or the treatment process it is currently undertaking. Here we list some of the possible causes of coloured drinking water.

BLUE

Blue or blue-green water can be indicative that copper has entered into your supply. Often this is due to water standing still in copper pipes giving the metal the time to dissolve into the water. Copper absorption can occur when the pipes in question are less than a year old and gradually reduce in time. What is more likely, however, is that your water is more corrosive than it should be and is causing damage to your plumbing. Corrosive water comes as a result of water which has a low and therefore, acidic pH. Although excessive copper consumption can have health implications, copper being present in your drinking water can be cause for other concerns as it can indicate that there is also lead in your water supply. Lead itself when dissolved in water is colourless, odourless and tasteless but is known to cause neurological damage when consumed above normally occurring levels. If your drinking water is blue or you know that you have copper piping supplying the water that goes to your taps, then testing for copper, lead and other metals as well as testing the pH of the water can give you valuable insight into any issues,

YELLOW

Tannins, which are chemical compounds and a byproduct of nature's fermentation process, can cause water to take on a yellow hue as it passes through vegetation which is decaying and peaty soil. Tannins are found in a vast range of other products including tea, coffee and wine, and do not pose a health risk. To treat this type of colouration, activated carbon filters and chlorination coupled with filtration are recommended.

RED

​If your drinking water is red or orange in colour, this may be because there is an abundance of iron in your supply. When iron is combined with water it creates red/orange particles which can cause unsightly staining on plumbing fixtures including your sink and bath, dishes and utensils, and clothing and fabrics which is rusty brown in colour.

Although the presence of iron in drinking water isn't considered to have any significant effects on health, it can alter other aesthetic properties of water, resulting in a bitter, metallic flavour as well as a sensation of dryness when drinking.

BLACK

​Black water coming from your taps can suggest that there is a build-up of hardness scale within your plumbing which has become stained over time by traces of manganese. For it to change the colour of your water, it will have likely become dislodged or disturbed, Whilst this water isn't known to be harmful, it is suggested that you avoid drinking it until it has cleared. Whilst this aesthetic change may not necessarily be a large issue in itself, it may indicate a larger issue with your water treatment and in particular, that your water supply requires softening.

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