James Brockett Water Excellence, Analysis

Domestic misconnections, in which household wastewater ends up in the surface drainage system rather than the sewers, are a nationally significant water problem.

Whether the result of ignorance, carelessness or sloppy workmanship, hundreds of thousands of toilets, sinks, washing machines or dishwashers are incorrectly connected into drains and channels that are intended to receive clean rainwater. It has been estimated by Defra that between 0.6% and 2.0% of households in the UK – or 150,000 to 500,000 households – may have some sort of misconnection. The most commonly misconnected appliances are washing machines (35%), sinks (20%) and dishwashers (10%), but 5% of instances involve a toilet being misconnected; cross-connections below ground can also be responsible for sewage mixing with surface water.

This waste ends up untreated in watercourses or beaches, impacting the environment and potentially public health. Nobody quite knows how much pollution in total is caused by misconnections, but there is little doubt that it is enough to negatively impact the status of many bodies of water under the Water Framework Directive. Yet because of the diffuse nature of the pollution caused, misconnections can lie undetected for years.

So where does the responsibility lie for resolving this problem, and what are water companies doing about it?

Andrew Broadbent, Environmental Protection Manager at Thames Water and chair of the National Misconnections Strategy Group, says that many misconnections can be blamed on dodgy DIY from householders.

“DIY is the only unregulated trade industry, so anybody can go to their local building supplies shop, pick up some pipework and modify any drainage they want on their home,” says Broadbent. “Most misconnections are above ground, although there are a proportion which are below ground which have been done either through error or convenience by building contractors, and the clients are ignorant of it.”

While misconnections can occur in any context – commercial and domestic, urban and rural – they are most associated with densely populated urban areas, and with homes built since the 1950s that have been modified from their original character by extensions, en-suite bathrooms, conversion from houses into flats, and so on.

“A lot of people are completely unaware that there are two separate systems for wastewater and surface water, and it probably isn’t helped that central London is a single combined system,” says Broadbent. “People have the incorrect perception that everything goes into the same drain eventually.”

The legal position: whose responsibility is the misconnection?

• Misconnections which are wholly on private land are the responsibility of the owner to put right. The power to enforce this lies with the local authority under Section 59 of the Building Act 1984, which states that drainage on private land must not cause an environmental nuisance or be prejudicial to public health.

• For these private misconnections, it makes no difference whether the misconnection is internal or external to the house, or is above or below ground. However, the position of the misconnection may indicate who was originally at fault for the mistake (e.g. a plumber or building contractor) which may give the householder grounds for legal recourse against them.

• Where a misconnection is outside the boundary (or curtilage) of a property, or occurs after the point where a property’s drains combine with those from neighbouring properties, then this is a public misconnection and is the responsibility of the water company to correct. Many of these drains and sewers were privately owned until the Adoption of Private Sewers Regulations in 2011 moved responsibility for them to water utilities

• Where a misconnection has been identified and a householder refuses to correct it, the local authority could ultimately decide to take them to a Magistrates Court to enforce the work under the Building Act. The penalties in such a case would involve paying for the cost of the work and legal costs

• In cases where significant pollution has been caused, the Environment Agency could also prosecute. However, it would have to be proven that an individual source was solely responsible for the pollution, which is unlikely to be the case for a domestic misconnection in a well- populated area.

Water company response

Most water companies in England and Wales have AMP6 projects which focus on improvement of environmental water quality in their local catchments – whether for inland watercourses or for bathing water – which include an element of highlighting and tackling misconnections. This type of proactive work typically forms a part of the River Basin Management Plan (RBMP) which water companies work on together with the Environment Agency, local authorities and other environmental stakeholders.

In addition, water companies will react to reports of pollution from the public, and where misconnections are identified as a likely cause this can be the spur for further action. In such areas a sustained campaign, with the help of specialist contractors, can uncover hundreds of misconnections and make a marked difference to environmental water quality.

“If we identify diffuse, light pollution that comes from multiple sources, it’s highly indicative that it’s misconnections or private sewer issues,” says Thames Water’s Andrew Broadbent. “In these circumstances, that could be channelled into a specific programme of work where we appoint specialist contractors to go out and do a methodical strategic approach to investigating the whole catchment. Misconnection discharges can be intermittent, depending on when the household has been using the appliance, so you can’t just look at a catchment at a single time on one given day, you’ve got to assess the catchment repeatedly over a period of time, and then follow it up with a survey of the individual properties down to the appliance level.”

Water companies typically use a combination of techniques in these investigations:

• Visual checks around surface water outfalls are usually the starting point for investigations. Sewage fungus – a mass of filamentous bacteria that grows in response to excessive nutrients in the water – is normally a clear sign of pollution, while the presence of grease and fat is often indicative of kitchen waste.

• The installation of temporary traps or screens is often then used to pick up tell-tale debris, such as kitchen scraps, bathroom waste or traces of detergent, that should not be found in a stormwater.

• Once at the property level, dye testing, where a harmless coloured dye is put into a sink or appliance to work out where it is connected to in the network, is the most commonly used way of establishing that a misconnection has occurred.

• Some utilities and contractors also use CCTV attached to crawler devices to enter the sewer network and follow its route towards the source of pollution.


While water companies, in collaboration with local authorities, can do a lot individually in their regions on tackling misconnections, there is also a sector-led national effort on awareness and educational campaign to prevent misconnections from happening in the first place.

The National Misconnections Strategy Group, which has representation from water companies across the UK, runs a campaign called Connectright (info at www.connectright.org.uk) to give the public information about how household drains should be connected.

One of the key messages of the campaign is persuading the public to use plumbers that are part of the water industry’s accreditation scheme, Watersafe (www.watersafe.org.uk) when making alterations to their pipes and drainage. Using an accredited plumber can reassure the customer that the plumber is conversant with WRAS water regulations and the risk of misconnections. It remains the case that the majority of plumbers do not come with this reassurance: only 5,500 plumbers are Watersafe accredited, out of an estimated 84,000 working in the UK.

Water company view: Brian Rousell, Project Manager, Southern Water

“Of the 83 bathing waters on Southern Water’s coastal strip, 54 of these are already of excellent quality. Of the remainder, there are a few that we acknowledge are long term projects, because they have bigger issues that we are working on. These leaves us with 21 bathing waters where we undertook to carry out a detailed investigation in AMP6 as part of our Bathing Water Programme, to find out what the root causes of pollution were. As a result of this work, we have identified seven bathing waters which we think we can take through to excellent by the end of the AMP; we are now in the delivery phase on this.

“There are a number of influencers on bathing water quality that we’ve identified, but the one that is a common contributor across all seven is misconnections. We sampled surface water outfalls at all of these locations, and where we’ve identified pollution then we start our misconnections campaign from there.

“We use a specialist contractor called WERM, who work with our delivery partner MWH, to do a tracing study. Essentially they install small chicken wire mesh cages in the pipes near surface water manholes, leave them for a period of time and then come back to see if there is any debris being caught in the cages. If there is sewage litter, or fungus, this suggests a misconnection. If it’s washing machines or dishwashers that have been misconnected, you might not get a lot of solid matter, but there will be some sort of deposit on the cage that will tell you what is going on.

“Where they find evidence of pollution they work back up the route of the network, a manhole at a time, to work out where it’s coming from. They will be able to identify part of a street as the source, so then it is a case of doing a door knock and asking to investigate.

“Sometimes you can see visually from the street that a house is misconnected – if you can see a rainwater gulley with a downpipe and you can see something coming out of the bathroom into the rainwater pipe, for example. But other misconnections are underground, so in that instance they would ask to do a dye test – putting dye into the pipes to see where it emerges – which will establish for certain whether there is a misconnection from the property.

“If the misconnection is on the public highway or on third party land – which might be 10-20% of cases – then it’s a public misconnection and it’s the responsibility of the water company to rectify it and our capital works delivery partner, which is MGJV [Morrisons Galliford Try joint venture] will carry out that work for us.

“But in the majority of cases the misconnection is a private one, and in that instance it’s the responsibility of the owner to rectify it.

“Of course you will find some householders who are reluctant or resistant, but the majority are interested and want to do something about it if they find out they are misconnected. It’s largely a lack of awareness that has caused the problem: people have just connected their dishwashers to the nearest drain and thought ‘that’ll do’. But if you tell them that their wastewater is going straight out onto the nearest beach, then that beach is local to them, so they’ve usually got a sense of ownership and pride about it. They will then be keen to get the problem sorted out.

“Across our seven bathing water sites that we are talking about here, there are six local authorities covering those seven sites. Since it’s the local authority’s environmental health team which has the enforcement power in this area, our approach with these private misconnections is to get as much information as we can and then pass that information on to the relevant local authority.

“For each of the six local authorities we’ve established a bathing water steering group for this project, and we are keeping the database of the misconnections that we’ve found and what status they are at, so that between us we can try and ensure that they are all rectified in good time. Our deadline for getting them all rectified will be the start of the bathing season in 2019. The councils we are working with have all been very enthusiastic and proactive, keen to get involved in this and see it through.

“It’s early days for the delivery of this project, as we only started a few weeks ago and have not reached all seven areas yet, but we have already discovered more than 100 misconnections including 15 misconnected toilets. We’re also looking at other sources of diffuse pollution – working with Natural England on how we educate agriculture, and working with the local authorities on issues such as dogs and birds on the beach, litter, and all those other things that can have an impact on bathing water quality.”

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