Four of the 10 water and sewerage companies in England and Wales—Northumbrian Water, Severn Trent Water, United Utilities and Yorkshire Water—charge non-household customers for surface water drainage according to impermeable site area. The remaining six—Anglian Water, Southern Water, South West Water, Thames Water, Welsh Water and Wessex Water—charge for surface water drainage according to the rateable value of a premises and/or include the charge in their standing charges and/or volumetric charges.