Issues with your water's colour

As well as making sure water is wholesome, water companies also have to consider if drinking water is acceptable to consumers in terms of its appearance, taste and smell to meet the Water Supply (Water Quality) Regulations.

If your water becomes discoloured

Despite our very high standards, your tap water can sometimes become discoloured or contain visible particles.

Usually, this is nothing to worry about – but check our information below to find out when to call us:

0330 303 0368

White, cloudy or milky water

White, milky, chalky or bubbly discolouration is caused by tiny bubbles of air.

It is quite harmless and the water will clear if you leave it to stand.

This happens when air dissolves in water under pressure. When the pressure drops as you turn on the tap, air is released and forms tiny bubbles (similar to opening a bottle of fizzy drink). As these bubbles slowly float to the surface, the water will clear. If you pour a glass of water, you should be able to see it clear from the bottom up.

Sometimes, white scum may form around the side of the glass. This is due to ‘surface tension’ where some of the tiny bubbles are trapped at the water surface which then stick to the inside of the glass. Sometimes, a faulty stop tap, or one that is partially open, can cause white water.

If the problem continues, please call us on the number above.

Brown or red water

Brown or red colour in water is caused by iron from sediment that has built up over time in older cast iron water mains.

To prevent this, we’re replacing or updating our pipes, depending on their age and condition.

Follow the link to find out more about testing for iron levels as part of the water quality standards.

If the problem has been going on for some time, please call us on the number above.

Dirty or raw water


Raw water drawn from surface sources can be discoloured. The intensity can vary depending on the season and the weather.

The discolouration is caused by natural dissolved organic matter and where this is the case, we make every effort to remove it at our water supply works. See how we treat water for more information.

Blue water

Blue discoloration can be caused by copper from the inside of storage cylinders or household pipes.

Possible reasons for this include poor earth leakage connections, pH and also high pressure boiler settings.

If you experience blue water, call us on the number above and we’ll arrange to have your water sampled and analysed.

Dark particles or purple spots

In certain areas, manganese may sometimes show up in your water as tiny black or brown flakes or particles.

It can also appear as tiny dark purple pin spots on laundry.

Please call us on the number above and we’ll be happy to investigate it for you, and flush out the local network if required.

Other causes of discoloured water

Check below to see some other reasons for discoloured water.

Work in your area

If the water from your cold kitchen tap (or other mains-fed tap) suddenly becomes discoloured, this could be because we’re carrying out some maintenance or repair work in your area, for example following a burst main.

If we haven’t let you know we're doing work in your area, and the issue continues, please call us on the number above. If we’re not working in your area, we’ll investigate and update you.

Change in your water's flow

Your water may become discoloured if the flow is affected.

There could be several reasons for this, for example, if the fire service is uses lots of water to tackle a fire, or if a pipe has burst.

This change in flow can disturb the sediment in water mains, enabling substances which cause discolouration (like iron and manganese) to get into water.

This is usually temporary and disappears once the network settles – running your tap for few minutes should clear it.

A problem with your water storage tank

 

If you notice discoloured water or odour from any of your taps not served directly from the public water main (not your cold kitchen tap, which should be supplied directly from the water main), you may have a problem with a storage tank at your property.

If you’re in any doubt, please call an approved plumber to investigate this. 

Make sure that your home storage tank has a close-fitting lid and is regularly cleaned.

 

Discoloured washing

Pink or black staining on surfaces

Check below for information and advice if you find staining on surfaces in kitchens, bathrooms and elsewhere around your home.

Other causes of discoloured water

Check below to see some other reasons for discoloured water.

Pink staining

Pink staining is caused by airborne bacteria called Serratia Marcescens – this is not known to cause waterborne disease.

How to deal with pink staining

Serratia do not survive in chlorinated water supplied from the mains. 

The heating action of showers and hot water systems can remove the chlorine put into mains supplies.

Without chlorine, bacteria can grow on surfaces such as tiles, grouting and shower fittings.

Once established, it’s difficult to totally remove the organism that causes pink staining.

  • The most effective way of controlling re-growth is by regular cleaning with a bleach-based cleaning product, paying particular attention to areas where soap residue may accumulate.
  • The cleaning process is generally more successful if the bleach-based cleaner is allowed to act for a while (about half an hour), before rinsing clean.
  • Using abrasive cleaning products tends to encourage re-growth as they cause a rough surface where the bacteria can take hold – this is often why Serratia is seen on grout but not on tiles, unless they’re covered in heavy soap deposits/film.

Other recommendations are to check (or get a plumber to check) that storage tanks which feed showers and internal plumbing are not open to the atmosphere.

Installing a securely-fitting lid should avoid dust and debris falling into the tank. We also recommend that the tank itself is checked for sediment and deposits and cleaned if necessary.

Deposits in the tank may reduce the amount of chlorine in the water and help create conditions in which bacteria like Serratia can grow.

More about pink staining
  • Serratia-type bacteria are found naturally in the environment and grow in moist, damp conditions such as those found in bathrooms and kitchens.
  • Serratia thrive in fatty deposits, such as soapy residue, and have also been known to grow in pet food bowls and on sinks.
  • All bacteria need nutrients for growth and anywhere that provides these nutrients in moist conditions has the potential for bacterial growth.
  • Serratia are usually detected in rooms where windows are open (commonly bathrooms).
  • They can become more of a problem after building renovations where dust and debris are released into the atmosphere.

Black staining

Black staining from water is typically composed of several different fungi.

Although unsightly, black stains caused by water don’t generally present a health risk – unless the fungal growth is allowed to continue unchecked and becomes very dense.

Then, any risk though would be from breathing in fungal spores (particular for those with illnesses such as asthma) – not from the water supply.

How to deal with black staining

The cold mains water supply contains a small amount of chlorine, which inhibits the growth of fungal spores.

However, water running through the internal plumbing system will gradually lose the protective effect of this residual amount of chlorine.

Once established, fungal growth can be difficult to get rid of.

  • Improving ventilation and keeping surfaces dry is the best way to prevent growth.
  • The most effective way of controlling re-growth is through regular cleaning with a bleach-based cleaning product, paying particular attention to areas where soap residue may accumulate.
  • The cleaning process is generally more successful if the cleaning product is allowed to act for a while (about half an hour), before rinsing it off.

Using abrasive cleaning products tends to encourage re-growth as they cause a rough surface where the fungi can take hold.

This is why black growth is often seen on grout but not on tiles, unless they’re covered in heavy soap deposits.

We recommend that storage tanks which feed showers and internal plumbing are checked to make sure they aren’t open to the atmosphere. Installing a securely fitting lid should avoid dust and debris falling into the tank.

We also recommend that the tank itself is checked for sediment and deposits and cleaned if necessary. Deposits in the tank may reduce the amount of chlorine in the water and help create conditions in which fungi can grow.

We’d also advise disinfecting and drying bathrooms and kitchen surfaces before leaving the house vacant for long weekends or holidays. Pouring a little household bleach into toilet bowls and down the kitchen sink will help slow down any re-growth.

More about black staining
  • Fungal spores are naturally present in the environment and being airborne, can be dispersed throughout buildings by air currents.
  • When they find a suitable warm, moist location with a source of food, the spores multiply and produce a grey or black ‘jelly-like’ growth.
  • In bathrooms, propellants from aerosols, hair spray, deodorants and soap residues provide a source of nutrients and can accelerate growth.
  • Also when houses are left vacant over long weekends, holidays or in between occupancy, fungal spores multiply.
  • The increased use of double-glazing and warmer buildings has contributed to fungal growth as there are less draughts, which help dry out the atmosphere.
  • Water without chlorine present provides the moisture that these fungi need to grow, so they are usually found places such as:
    • the end of cold water taps (usually kitchen or bathroom) such as the plastic inserts in kitchen taps
    • inside washing machines, particularly around the powder drawer
    • filter jug hoppers and their elements
    • inside kettles, if water is left for long periods
    • toilet cisterns and bowls, for example up under the rim and inside the cistern
    • shower heads
    • around tiles and sealants in bathrooms and shower rooms
    • on shower curtains or towels (where they often appear as black spots or staining)
    • in waste traps connected to sinks
 
 
 
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