A Changed Approach To Surface Water Drainage

When it comes to surface water drainage, there’s a new school of thought that instead of relying on traditional sewerage systems, pipes and hard engineered structures for drainage, it may in fact be better for rainwater falling on roofs and hard standing around houses to infiltrate into the ground, instead of going into a piped sewer system.


In a new white paper, Water UK explains that the aim behind this idea is to mimic the natural processes by which runoff is absorbed by the land through techniques known as sustainable drainage systems.


This would reduce the chances of pipes overflowing during heavy rainfall but also create more headroom in our sewer systems, which would in turn allow for more housing development.


A number of water and sewerage companies around the UK have already recognised the benefits of this approach, which include the creation of more green spaces and absorbing different pollutants in surface water.


Although some suppliers have already taken steps to do more in this regard, there has never been – until now, that is – a nationally agreed strategy from companies relating to the transfer to them of these types of sewers.


Water UK has now developed a new guide to adoptable surface water sewers, and water and sewerage firms are now readying themselves to accept adoption applications under a new set of standards. The date that these will come into force will depend on Ofwat and the period the industry regulator needs to approve the new arrangements – but this is not expected to take place before the middle of next year.


Examples of adoptable asset types include detention basins (where water flows in through an inlet, carried through the channel so some of the flow can infiltrate into the ground before being discharged through a pipe to a stream or similar), and rills (an architectural landscape feature where property roof water drainage and footpath runoff is diverted to vegetated channels).


For businesses around the UK, you will be charged for the drainage of any rainwater on your property and unfortunately the charges levied by some suppliers are far from an accurate idea of how much surface water companies need to dispose of. And thousands of organisations are routinely overcharged because of fixed and inflexible pricing structures.


You can take steps to reduce your costs, however, by reviewing your historic water bills for all your sites. These will be analysed to work out the rate you’re being charged for drainage and the method that your water supplier is using to calculate it.


A water audit can also be carried out of your property to work out the number of roof gutters and road or path runaways. Taking into account estimated average rainfall, we can work out a ballpark figure for drainage volumes and compare this against your bill to see if there are any discrepancies between your charges and what your drainage needs are likely to be.