Water and sewerage companies have to remove and process the rain water which falls on properties and then flows directly or indirectly into the public drainage systems. This is known as surface water drainage.

Calculating the precise costs of dealing with surface water is not simple at an individual customer level. In the past companies based their charges on the rateable value of the premises. However, rateable values are not a good indication of how much surface water may drain from a property.

Charging in relation to surface area is fair

In 2003, following a review of the various options, we recommended that charging in relation to site area is the fairest approach. In general, you should only pay surface water drainage charges for the site area where water drains into public sewers. This means that your water company will not charge you for areas where there is natural drainage, such as playing fields, as long as the area of these makes up a significant proportion of your total area (usually 10 percent).

The larger your site area, the more surface water is likely to drain from it. Therefore, charging by site area better reflects the actual costs imposed on the system by customers. In the previous charging system, some customers subsidised others. There was an unfair situation where a small city centre newsagent could in effect end up paying in part for services used by a large out-of-town factory.

Site area based charging also offers financial incentives for all organisations to reduce their surface water drainage, this will reduce the likelihood of flooding from overloaded sewers.