Warning: You are using an outdated Browser, Please switch to a more modern browser such as Chrome, Firefox or Microsoft Edge.

Water pollution arises from the release of a harmful substance into a body of water which adversely affects the water environment. Some substances such as oils, solvents, silts, milk and detergents have the capacity to cause considerable and long lasting damage even if only small quantities are lost.

The body of water could be a river, stream, ditch, dyke, lake, pond, groundwater or coastal waters; these are known as ‘controlled waters’ in law. The pollutant could be a solid or a liquid and whether or not pollution occurs will largely be dependent upon the quantity and concentration of the substance released.  For example 1 litre of oil can contaminate a million litres of water.

All businesses are required to work within a framework of Acts and Regulations which vary from region to region within the UK as do the respective regulatory bodies.   


Any business releasing any form of pollutant into controlled waters must have consent from the enforcing authority, or if releasing into the foul sewer needs consent from their water company.

These consents will specify limits for each substance to be discharged and will set out maximum volumes, place of discharge and any monitoring arrangements.

Failure to comply with conditions of the consent is an offence, as is the failure to obtain a consent. Additionally, failure to comply with conditions of the consent when discharging into a foul sewer may overwhelm the sewerage works and cause pollution in a receiving river or stream.

The systems for storage, handling and transfer of substances on site need to be identified and assessed, especially bulk storage tanks and associated pipework from any waste products.

Most sites are serviced by drains leading to foul sewers, surface water drains or soakaways and a site drainage plan is essential as it will show whether the drains connect to the foul sewer or not; this should be part of any environmental management plan for a process that requires an environmental permit.

The drains on site should be colour coded or suitably marked to show whether they are surface water or foul:

  • blue for surface water, 
  • red for foul, and 
  • a red ‘C’ for a combined system where all water goes to a treatment plant