Surface water drains: what you need to know

Believe it or not, sewer connections aren’t all equal – usually owing to where they’re located and how recently that area has been developed.

Initially, when the first drainage infrastructure was created in urban areas during the 19th century, sewer connections were combined. The emphasis was on solving the sanitation problems of cities, and quickly combating diseases such as cholera. As such, huge Victorian sewers were built to handle all waste. Both surface-water run-off – the rain that falls on roofs, roads, and other areas of hardstanding – and effluent from both domestic and commercial properties, flowed along the same pipe.

Combined sewer connections are now part of our history

These days, combined sewer connections wouldn’t get past the water authorities’ approval process. It’s now mandatory to have separate pipework for both surface water run-off and sewage from homes and businesses. The surface water drains carry uncontaminated water away and into streams, rivers, and the sea, while other pipes take effluent to be treated at sewage works.

That all being said, there’s still some distance between the theory and reality due to the fact there remains a significant issue throughout London, Essex, Hertfordshire, Kent and Suffolk (along with the wider UK) with the misconnection of sewers. Just to give you an idea of the scale of the problem, Thames Water estimated that 55m tonnes of raw sewage gets washed into the Thames in a year. That’s a lot of pollution!

Surface water and foul drains

How does such pollution occur? Well, it’s sometimes easier and more convenient for (cowboy) builders and plumbers – or even DIYers, whether deliberately or accidentally – to connect kitchen wastes into rainwater gullies, which tend to be located fairly close to where kitchen or bathroom extensions are likely to be built, especially if they are Victorian sewers.

Similarly, in more modern builds, it can be a lot easier to connect rainwater goods to the foul drains – and though this doesn’t cause pollution, it does mean that the mains sewer has to cope with a greater volume, and this adds to all our water bills through the additional costs of maintenance that the water authorities have to factor in.

If you suspect that your property’s drainage has been incorrectly connected, it’s important to get it checked by a professional, and any errors corrected, because water authorities can and do issue fines. You can call us on 01268 950050 for free and impartial advice on your drainage connection.

Surface water drains: the alternative

Most water authorities will only accept surface water into a public sewer if there are no alternatives, and the onus will be on you to prove there is no alternative when you make your Section 106 application.

The most common alternative for connecting surface water drains to the surface water sewer is a soakaway – this is a specific point where the run-off can soak into the ground, away from the property, to become part of the water table. It’s basically a hole or trench that has been dug and filled with either stones or plastic crates designed for the purpose.

If a soakaway isn’t feasible, and it’s not possible to make separate connections for foul and surface water drains, most water authorities will ask you to provide evidence that this is the case, which could include an extract from a ground investigation report, the results of a percolation test, or an email or letter from Building Control.

If you are connecting to a Victorian combined sewer, there may be an exception made. Often, you would be asked to keep the foul and surface water flows separate until the point where the drainage leaves your property’s boundary, and then goes into a combined manhole, so that only one length of combined sewer is present. This ensures that if sewer upgrades are carried out, the flows are separate, and the area can be properly upgraded.

Discharging sewers as surface water

Obviously, this can only happen under very specific circumstances. If a property is not close to any public sewers, then the best option may be to install a private treatment plant, which can legally discharge into a watercourse. The treatment plant must be designed to meet BS EN 12566 requirements, plus be specified and installed correctly. You can find more information about this on the Government’s website, while British Water publishes a useful guidance document on sizing.

At Premier Drainage Solutions we’ve seen it all, and more! We can help you to find the best solution to your sewer connection requirements. To find out more about our problem-solving approach to sewer connections, whether in city centres or remote rural areas, and for free advice on your sewer connection works, call 01268 950050 or send us an email to [email protected].

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