Drainage misconnections: ensuring water quality

Course of action

10 October 2014

Checking for drainage misconnections is vital to ensure that water quality is not compromised, explains Ian Myers

People often think that water pollution is caused by industry or businesses acting irresponsibly and taking short cuts. However, the truth is that our homes, properties and lifestyles also have significant impacts on the environment. In many parts of the UK, pollution of rivers and beaches is being caused by drainage misconnections where sinks, washing machines, baths, showers and even toilets are incorrectly connected to surface water sewers. This results in the discharge of untreated sewage, with often serious consequences for wildlife and amenity.

There are different types of sewerage systems for clean and foul water, with just under half of all properties being served by separate sewers and a consequent risk of misconnections.

Problems are also caused when clean surface water drains from roofs and paved areas are connected unnecessarily to foul drainage systems. So-called 'clean misconnections' cause increased pumping and/or treatment costs and take up sewer capacity.

Clean misconnections cause increased treatment costs and take up sewer capacity

They also cause overflows into rivers and occasionally into properties in times of wet weather. This was particularly evident after the intense rainfall of summer 2012.

Most above-ground misconnections are relatively easy to spot, but surveyors also need to be aware of the possibility of blocked, damaged and leaking drains below ground. Below-ground drainage problems can lead to structural problems, cause groundwater pollution and create capacity issues in times of wetter weather. With the future expected impacts of climate change, drainage is increasingly important.


Once identified, the responsibility to rectify drainage usually rests with property owners. While most misconnections are fairly simple and cheap to fix, some below-ground problems can be complicated and expensive. Building Control approval checks for new developments are also important to ensure that drainage is installed properly and connected to the right type of sewer.

The responsibility to investigate and ensure that misconnections are addressed is divided between:

  • Local authorities: under Section 59 of the Building Act 1984, they have the power to serve notices to rectify misconnections or under Section 259 of the 1936 Public Health Act to address a statutory nuisance
  • Environment Agency: with an overall duty to protect water quality, it can serve Anti-Pollution Works Notices under Section 161 of the Water Resources Act 1991 to rectify problems and/or prosecute for causing pollution
  • Water companies: as owners of many surface water sewers, they have a role to investigate misconnection problems and pollution from their assets.

Misconnections and damaged drainage affect water quality, impact on amenity and put public health at risk.

The UK has to ensure 'good ecological status' for all designated watercourses by 2020 under the Water Framework Directive and the Environment Agency is now working with many organisations to achieve this. For people living in Britain's cities, urban rivers and streams can be one of the best ways to interact with the natural environment. Studies have also shown that access and proximity to green spaces can have a positive effect on property prices and wellbeing.

It is estimated that misconnections impact on around 9% of the UK's beaches designated under the EU Bathing Water Directive. They also threaten the quality of shellfish water, where there is a need to comply with certain bacteriological standards. In much of the south and east of England the majority of drinking supplies come from groundwater.

Scale of problem

A UK Water Industry Research project recently estimated that there are up to 500,000 misconnections across the country, but this is perhaps a conservative figure. Investigations by water companies find an average of 2.3% properties are misconnected.

Misconnections can be very common in properties of a particular age with certain design features. The typical 'box four' semi-detached properties built either side of the Second World War usually on separate drainage systems can lend themselves to kitchen and bathroom modifications and hence misconnections.

Drainage misconnections can also be found in newer properties where kitchens and bathrooms have been resited and connections made to the nearest or most convenient sewer. Macerator pump units allow easy installation of an appliance or sanitary convenience, where previously drain access made this impossible.

The trend for DIY house renovations and increasing numbers of multiple occupation properties have all added to the problem. Even if undertaken by professional builders, alterations can be misconnected. Efforts are being made by the Environment Agency, water and sewerage companies, and other key partners including RICS, to raise awareness with the public, white goods manufacturers, plumbers and builders.

System checks

In particular, RICS surveyors undertaking home surveys need to check property drainage to identify any potential misconnections, particularly where there are known to be separate systems. This will usually only require a low level of awareness to spot obvious above-ground pipework but in some situations may include dye testing and more in depth CCTV surveys to confirm connections and drainage conditions.

Increasingly, in areas served by combined drainage, local authorities and water companies are now requiring storm drains to be directed to soakaways to maximise foul sewer capacity. It cannot be assumed that there is no risk in all combined drainage areas.

Survey pointers

Misconnections are an issue about which surveyors should be aware due to the possible damage to the environment, rivers, seas (bathing) and wildlife. Drainage problems cause pollution and structural problems with properties. It is not only 'foul to surface' wastewater that cause problems but also 'clean misconnections'.

It is important when carrying out any type of survey that drainage is considered, potential problems are spotted with connections checked and confirmed wherever possible. Pollution or problems could lead to prosecution or difficulties for the owner and leave them with the burden of carrying out corrective works.

Surveyors, therefore, need to be observant and check drainage as a matter of course during inspections and advise their clients to rectify any drainage problems accordingly. If they need help from experts then they should ensure they appoint competent drainage contractors.

Alan Cripps FRICS is an Associate Director of the RICS Built Environment Group

Surveyors need to be aware of the risks from damaged drains, which can be a source of problems other than the obvious unpleasantness from failures and blockages.

The majority of private drainage systems are built of clay and can be up to 100 years old but many are newer and can be made of more vulnerable material such as pitched fibre. Drainage can commonly suffer from joint displacements, fractures and breaks – all of which allow exfiltration and infiltration of liquids or groundwater. Over time, this flow can wash away the fine material from the surrounding earth and result in voids being formed. What starts as a relatively minor issue can deteriorate to become quite serious.

Repair options

At some point, such leaking drains are likely to require repair or replacement but there may be a detrimental effect on the building or adjacent properties and nearby roads. Any kind of underground erosion close to building foundations can lead to serious structural issues.

Domestic drain repair has advanced significantly over the past decade. No-dig technologies are increasingly used to reline complete drain lengths or patch localised defects, restoring drains to 'as good as new' condition. The main benefit of no-dig is the avoidance of excavation. Repairs are completed from a manhole or chamber, often in one working day, so reducing disruption to the homeowner.

Any kind of underground erosion close to building foundations can lead to serious structural issues

A property survey will typically cover the interior, exterior, services (i.e. gas, electrics and water) and the surrounding grounds. Drainage surveys, in the form of CCTV investigation, are also regularly recommended,  especially if there are signs of movement or damp. Some surveyors recommend these as a matter of course because drains are difficult to survey without the correct equipment or expertise. This additional work is normally completed by specialist competent drainage contractors.

It is important that drainage surveyors are aware of pollution issues and current guidance, such as the 5th edition of the Manual of sewer condition classification. The use of industry standard reporting software should also be encouraged to ensure the CCTV condition report provides adequate images, defect grading and colour coding to comply with water industry specifications. Importantly, this should make it easy for the customer and/or surveyor to understand and use.

Including a drainage survey as part of any survey or home buyer pack makes perfect sense for all parties.

There are numerous reasons why a drain survey might be recommended by a property surveyor, from obvious or suspected problems, to establish ownership or as a result of a mortgage lender or insurance company request. Whatever the reason, such work should be carried out by a competent contractor.

Ian Myers is Misconnections Campaign Manager at the Environment Agency

Further information

Related competencies include: Pathology, Inspection