Drains and sewers
Each property is connected to a drain; this is the responsibility of the property owner. The drain is connected to a sewer in the street or road near the property.
In most cases this will be a public sewer; it belongs to us and is our responsibility. In some cases the sewer is a private sewer and is the collective responsibility of the people it serves. Find out more about private sewers.
Sewers work by using gravity to carry the sewage to a sewage treatment works. This is easy in hilly areas - the sewers follow the line of the hill to provide the gradient. In flat places the sewers need to be dug ever deeper to provide the gradient needed to transport the sewage. Sometimes gravity can't be used and pumps are needed to push the sewage on its way along pipes called rising mains.
Simple sewerage system diagram
Sewers can be constructed of a variety of materials, including bricks, concrete, earthenware and plastic, and they range in size from at least 10 centimetres to several metres in diameter. Rising mains are made of metal to enable them to withstand pressure. In total we have almost 16,000 km of sewers.
There are two different sorts of sewerage systems - combined and separate - and three sorts of sewers.