Understanding illegal drain connections

Multiple pipe system

If your drain is connected to the wrong sewer, you can cause serious pollution to the clean water supplies other people are using. Not only is this unhygienic, it can be downright dangerous. A ‘misconnection’ or ‘cross connection’ is illegal, and as a homeowner or business owner, it is your responsibility to make sure that your drains are connected to the right sewers.

Illegal connections are a more common occurrence than you might think, with one survey conducted highlighting that 275 appliances were misconnected in Finchley and a staggering 975 – including 26 toilet – cross connections were identified in Muswell. Working on these statistics, Thames Water estimated that there may be as many as 60,000 illegal connections across its area. With such high numbers, and such cause for concern, this month Express Drainage Surveys are taking a closer look at illegal connections, how they might occur, their dangers and how you can go about identifying whether your drains are connected correctly.

How misconnections occur

Pipes connected underground

Misconnections often occur purely by accident, with the installers failing to correctly identify the difference between storm or surface drains and foul drains. Surface drains are intended for rain or snow and are connected to local rivers or oceans, so it really is paramount that your wastewater does not end up on this course. Foul drains are intended for any kind of wastewater including from toilets, baths, showers, sinks and washing machines, so none of these appliances should be connected to a surface drain.

The dangers of misconnections

The wastewater from all of our appliances and fixtures can be hugely detrimental to the environment, local wildlife and our own health. A misconnected toilet is an obvious concern, with untreated wastewater and faeces travelling to the nearest watercourse, where it will be used alongside clean water. This is both unhygienic and could cause parasites; there have even been instances of oestrogen affecting the hormones of wild fish after contraceptive items have been mistakenly flushed while a drain was misconnected.

Chemicals from your shampoo and conditioner from a misconnected shower, or even the strong detergents from your dishwasher or washing machine, can be severely harmful to the environment, damaging the local plants and wildlife and causing pollution problems.

The organic material making its way down your kitchen sink is also a big concern as the materials cannot be broken down by the naturally occurring bacteria in environmental waters. However, as the bacteria attempt to break down the material, they use up the oxygen in the water, and as the oxygen levels drop, fungus begins to grow. As this problem escalates, the river will no longer be able to support the fish, insects or wildlife that live in or around the water source.

The problem with misconnections does not only lie with the sewage in our rivers; misconnections that result in surface outlets attached to foul sewers are also a huge problem, leading to flooding and pipes breaking under the increased strain, so it is vitally important that both storm and foul drains are correctly connected at all points.

See also our article “Signs and causes of blocked drains: A Room-by-Room Guide

The law

Misconnected drains were made illegal by the Environmental Act 1990. The responsibility to rectify a misconnection lies with the current property owner, no matter when the drain misconnection occured. This means that it is your legal obligation to have the drain rectified. If you fail to do so, legal action will be taken. You will need to contact your local authority who, because of the health and environmental implications of this issue, will usually be willing to help with the problem voluntarily. However, if you fail to correct the drain after a notice has been served to you, you could receive a £50,000 fine, imprisonment of up to 12 months, or both if sentenced at a Magistrates Court. For more serious cases, the Crown Court can issue an unlimited fine, imprisonment of up to 5 years, or both.

Identifying a misconnection

If you’re concerned that your drains are misconnected, or simply want to make sure that you’re complying with the law regarding this issue, a CCTV drain survey is the quickest and easiest way to check.

A small, high-tech camera on a flexible rod will be pushed through your drains to discover which systems they are connected to. This isn’t invasive and does not damage your pipes – and is certainly a cost-effective way to avoid fines and prosecutions and put your mind at rest.


Express Drainage Surveys offer high quality CCTV surveys of drains of all sizes. We use our state-of-the-art equipment to produce evidential reports on the condition of pipes to provide clear, precise insight into any drainage issue you may be facing. Alongside this, we’ll be able to provide your insurance firm a copy of our findings to move along the claims produce quickly and help you find the right solution for your drainage malfunction. Get in touch today to book your CCTV drain survey.