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News & insights

news: 17 August 2017

Does surface water from the property drain to a public sewer?

Jason Harper, Account Manager

This is one of the questions in the Con29DW. But why is there such a question in the first place?



Since the transfer of a number of private sewers in October 2011, local water companies became responsible for their maintenance. Since 2017, SuDS (Sustainable urban Drainage Systems) have become more significant owing to the impacts of climate change and increased development in already urbanised areas. With these new developments, itís highly likely that surface water sewers will not be adopted by the local water companies because of the SuDS system thatís been put in place by the developer. This is something that any buyer needs to be made aware of, as there will be a maintenance charge for the upkeep of the grounds and the SuDS system itself.

Here are a few hints and tips from Susdrain.org

SuDS principles

Sustainable drainage is a departure from the traditional approach to draining sites. There are some key principles that influence the planning and design process enabling SuDS to mimic natural drainage by:

  • Storing runoff and releasing it slowly (attenuation).
  • Harvesting and using the rain close to where it falls.
  • Allowing water to soak into the ground (infiltration).
  • Slowly transporting (conveying) water on the surface.
  • Filtering out pollutants.
  • Allowing sediments to settle out by controlling the flow of the water.
Surface water is a valuable resource and this should be reflected in that way it is managed. It should be considered from the beginning of the development process and then throughout, influencing the design and layout of any public open space, or transport network, for example. It is important, where appropriate and particularly on larger developments, that teams (planners, engineers, landscape architects) work together from the outset.†

SuDS management train

A useful concept used in the development of sustainable drainage systems is the SuDS management train (sometimes referred to as the treatment train). Just as in a natural catchment, drainage techniques can be used in a series to change the flow and quality characteristics of the runoff in stages.
The management train starts with prevention (preventing runoff by reducing impermeable areas), or good housekeeping measures for reducing pollution; and progresses through local source controls to larger downstream site and regional controls.

Runoff need not pass through all the stages in the management train. It could flow straight to a site control, but as a general principle it is better to deal with runoff locally, returning the water to the natural drainage system as near to the source as possible.

Only if the water cannot be managed on site should it be slowly conveyed elsewhere. This may be due to the water requiring additional treatment before disposal or the quantities of runoff generated being greater than the capacity of the natural drainage system at that point.

SuDS design requires a balancing of different options, often depending on the risks associated with each course of action. The risks of an area flooding have to be balanced with the costs of protecting the area from different levels of floods.


So what?

What if you donít think about surface water before you develop? What if you decide not to work together with an interdisciplinary team on those larger developments? What if you donít jump on the SuDS management train? How are you going to make sure the surface water drains into a public sewer?†

My advice to youÖ Think about the benefits of SuDS on your development:

  • They can help create attractive corridors in developments, connecting people and the environment to water and open spaces.
  • They provide attractive public open spaces, improving the quality of life and creating a better community.
  • They help mitigate and adapt communities to climate change and are able to contain extreme weather events.
  • Most importantly from an environmental point of view, they donít need energy or pumping and reduce the demand on existing traditional sewers and downstream water treatment.



If youíd like to discuss further and find out how you can benefit from SuDS, please contact me via Jason.harper@thameswater.co.uk


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