Discoloured water

Drinking water is normally clear and bright in appearance but very occasionally it may temporarily appear discoloured and or contain particles. This often occurs after essential maintenance on the network of pipes that bring water from the treatment work to homes, for example, the repair of a burst water main. However, sometimes when the problem keeps occurring it is a sign that the underground supply pipe which brings water from the main in the highway into your property is in poor condition or that harmless deposits have accumulated over time in areas of low flow in the local water main.

What causes discoloured water?

Disturbance of harmless deposits, which have accumulated over time in the water pipes can make the water brown/black, orange, or white in appearance. White water can be the result of chalk deposits or very small air bubbles that make the water look milky. The root cause of this is a change in the direction or speed of water flow in local pipes or the entrainment of air due to operation of pumps and valves in the local network. Common causes of such events are listed below;

  • a burst or fracture on a water main or pump;
  • the opening or closing of valves on the network;
  • the reinstatement of a main after repairs or installation of new fittings;
  • the changing of the settings of valves to bring water into the local network from another part of the system to meet changes in consumer demand;
  • the use of water by third parties such as the fire brigade and road washing operators;
  • the laying of new water mains in the neighbourhood.

Sometimes discolouration is not due to the activities of water company operations and pipe condition, but instead it is caused by:

  • the condition of the service pipe connecting a property to the water main;
  • the condition of the domestic distribution system with a premises (including the plumbing inside a property);
  • in high rise properties the operation of internal booster pumps;
  • the operation of outside or inside stop cocks to facilitate the installation of new plumbing or to effect plumbing repairs.

All of these situations may turn the colour of the water yellow, orange, brown, grey or white. White water may be due to air entrainment (very small bubbles) and or suspended chalk into the water. Additionally, there may be brown, red, black particles in the water.

The cause of white water can be easily diagnosed by filling a glass of water from the tap and observing it for a few minutes. If the cloudiness clears from the bottom up on standing this is air and it is not something to be concerned about. However, if it occurs repeatedly then it should still be reported to your water company as this will help them to diagnose and fix the root cause.

Why are there deposits in the water mains?

There are two basic reasons for the build up of deposits.

  • Most of the older water mains in England and Wales are cast iron. Originally these were unlined and over time they corrode giving rise to iron particles (rust) which become loose and are carried along with the water flow until they lodge in areas of low flow in the network (known as dead ends or null points).
  • Some ground waters and soft surface water sources contain naturally occurring iron and manganese. A lack of adequate water treatment historically will have resulted in iron and manganese entering the mains network. Similarly in very hard water areas there can be a build up of chalk in the mains.

Are these deposits harmful to health?

If your tap water suddenly becomes discoloured, you should not assume that it is safe to drink until you have sought advice from your water company. The water company will be able to tell you if this is the result of the disturbance of deposits in the main due to a known short-term incident affecting your supply. It will also advise you of any work it is undertaking or intending to undertake to clean and refurbish water mains in your area. Sometimes, pending an investigation of the cause of discoloured water, the water company may need to issue a warning notice asking consumers to boil the water or restrict usage until it is satisfied that the water is safe to consume. In these situations the water company will tell you when any restrictions of use have been lifted and you can stop taking any precautions.

Is anything being done about this?

Water companies maintain their distribution systems to minimise the build up of deposits in the mains by carrying out flushing and by careful operation of valves, and  by giving licences to third party operators. Water companies are tackling the problem of iron corrosion by identifying the affected mains and then lining or replacing them. The worst affected areas are prioritised over others with a lower risk of discoloured water. Long-term 10 – 20 year programmes of mains refurbishment have been in place since 1995. However, there are about 315,000 kilometres of water mains in England and Wales and maintaining them will always be an ongoing process.

What should I do if I get discoloured water?

If you and your neighbours experience discoloured tap water, then contact your water company immediately. Enquiry and emergency numbers can be found on water company websites or on the back of your water bill. You can also find a general number for your water company on our website.

It is always a good idea to put aside a sample of the discoloured water in a clean glass bottle or jar, seal it and store in the fridge so you can show it to the water company when they visit. Please make a note of the date and time you took the sample. It is also helpful if you make a note of each time that you notice the problem.

If the water company does not give you a satisfactory explanation or the problem persists after any corrective action (flushing, mains repair) and you have checked that the problem is not due to pipes and water fittings for which you or the property owner is responsible, then you should contact your local Consumer Council for water (CCWater) office. You will find their contact details here. CCWater may ask the Inspectorate to investigate your complaint.

Your water company is required by law to notify the Inspectorate of any widespread incident involving discoloured water. We then investigate the water company’s activities and assess whether these have been appropriate. If necessary, the Inspectorate will require the company to take further action to remedy matters.

When only your property in your street has been affected by discoloured water, you are advised to contact a qualified plumber to help you identify and rectify any defects on your pipes and fittings that may have caused the problem. You should always use a plumber registered with the Institute of Plumbing or approved by your water company to ensure their work complies with regulations and your plumbing does not give rise to contamination or waste of water.

What will the Inspectorate do if I get discoloured water?

When we investigate a discoloured water incident or complaint, we independently assess and audit the water company’s technical records. We have powers to require the water company to carry out any work needed to rectify the problem and prevent it from happening again.

Exceptionally we may start prosecution proceedings if:

  • we can demonstrate evidence that the drinking water supplied was unfit for human consumption;
  • we consider that the water company did not do all that it might reasonably have been expected to do to prevent the discoloured water.

For those cases that do not justify full court proceedings we can issue a caution. The court can take cautions into account in any future offences.

In bringing a prosecution we may ask for your help by agreeing to be interviewed by one of our Inspectors to prepare a witness statement about the quality of your drinking water. This will include gathering details about what you observed and when and the consequences this had for you.

What about compensation?

We are not able to assist with any claims for compensation from water companies. You should contact the CCWater for such enquiries.

Back to top