Cookie consent

We use cookies to track how you use our website to help improve your experience and show you personalised content. You can accept the use of all cookies or manage them individually. You can find out more about your options by clicking “manage cookies".

Strictly necessary/functionality cookies

Necessary cookies enable core functionality. The website cannot function properly without these cookies, and can only be disabled by changing your browser preferences.

Find out more about our cookies

What is a misconnection?

A misconnection occurs when a building's drains are incorrectly connected to the sewer network. This can occur as a result of incorrect plumbing, which is often unintentional, but can cause multiple issues for the sewer system and local waterways.

Modern households typically have two types of drains that take water away from the property:

  1. Foul drain– this drain takes wastewater from toilets, sinks, showers, baths, washing machines and dishwashers to a wastewater treatment works where it is cleaned and treated so it can be safely returned to rivers and the sea.

  2. Surface water drain– this drain takes rainwater direct to local watercourses, streams and rivers.

The diagram below shows the foul and surface water sewer systems. The brown pipework shows wastewater from the house entering the foul sewer, which will flow to the nearest wastewater treatment works. The blue pipework shows rainwater which will drain straight to a watercourse or the sea via the surface water sewer.

Drains and sewers explained - separate sewer systems diagram

It’s really important that toilets, baths, showers and water-using appliances, such as washing machines and dishwashers, are all connected to the foul drain. If appliances are connected to the rainwater or surface water drain, the foul wastewater will go straight into local watercourses leading to a pollution incident.

This diagram shows how the shower, toilet and washing machine have been misconnected to the surface water system resulting in a pollution incident to the local waterway.Misconnections diagram

  • The Department for Environment, Food and Rural Affairs (DEFRA) estimates that between 150,000 and 500,000 households in the UK have misconnections. The most commonly misconnected household appliances are washing machines (35%), sinks (20%), dishwashers (10%) and toilets (5%).

    A “foul-to-surface” misconnection means that used or dirty water will go straight into local streams, rivers and eventually the sea. Unfortunately, this can pollute the local environment and cause harm to marine and plant life in watercourses.

    A “surface-to-foul water” misconnection can increase flows to and overwhelm the wastewater network, leading to increased chances of property flooding and sewer overflows operating.

    For example, a misconnected kitchen sink can result in detergents, bleach, cooking oil/grease and food waste going straight into the environment, putting wildlife and natural habitats at risk.

  • It is the legal responsibility of the property owner to make sure a misconnection is put right. If you are renting your property, please contact the landlord and make them aware of the issue.

  • Here at United Utilities, we are committed to protecting rivers from pollution to create a stronger, greener and healthier North West. We work jointly with the Environment Agency to combat the issue of misconnected household drains.

    Once a contaminated watercourse has been discovered, where the foul wastewater is going where it shouldn’t, the pollution can be traced back to the property where the waste pipes are misconnected using techniques such as dye-tracing and closed-circuit television (CCTV) surveys of the pipes.

    This involves putting a coloured dye down a household’s drains, sinks, toilets etc which enables us to track the flow of wastewater and confirm if there is a misconnection at the property. If we do find a misconnection at a customer’s property, we will get in touch with more information to help the customer locate and fix the misconnection.

  • You can play your part in protecting the environment by making the right connection to waste drains.

    If you’re planning some home improvements, for example, moving your washing machine into a new location, such as the garage, or building an extension to your home, it’s important to make sure any wastewater pipes are plumbed into the correct drain. You can check your drains are properly connected by visiting Water.org.uk.

    As the property owner, it is your responsibility to cover the cost of fixing misconnections. To avoid incurring any unnecessary costs and further work at your property, ensure you are using a trusted trader for any home improvements you are making.

    WaterSafe Logo

  • Make sure your pipes are connected correctly

    You should contact a qualified plumber who will be able to carry out the work necessary. It’s a good idea to choose someone who is a member of an approved contractors’ scheme. You can go to watersafe.org.uk and type in your postcode to find your nearest plumber.

    Alternatively, drainsafe.org is an industry led contractor scheme which provides you with confidence that your contractor is qualified to do their work. You can find their list of approved contractors here.

    If you have any more questions about misconnections, please contact us.

Making the right connection

Take a look at this video which shows how misconnected drains can pollute the local environment and cause harm to marine and plant life in our watercourses.