Drains & Sewers

New rules for septic tanks and small sewage treatment plants

What are Sewers and Drains?

There are two kinds of wastewater, foul water, and surface water. The two must be kept separate and the one not discharged to the other.

  • Foul Water - Toilets, sinks, baths, showers and kitchen appliances make up the foul waste water discharge. This must outfall either at a place where it can be properly treated or stored for disposal at a later date. This could be a public waste water treatment works or a private cesspool, septic tank or bio digester unit where it can remain until discharged into the environment or taken away in tankers for further treatment.
  • Surface Water - Water issuing from roof down pipes and drains in driveways or open paved areas on your property make up the fresh surface water discharge. This may be connected to a system of pipes forming a surface water sewer, be directed to a soakaway or straight to a water course. Occasionally on some older properties both the foul and surface water discharge may be combined. 

Drain - A drain is a pipe taking foul or surface water flows from one property.

Sewer - A sewer is a pipe taking foul or surface water flows from two or more properties.

Sewage - Is the effluent or water that passes through the sewer or drain.

Sewerage - Is the system or network of pipes that form the sewer connections from head to discharge at the treatment works or some other final outfall.

Public or Main Sewer - A public or main sewer is part of the network of publicly owned foul or surface water drainage systems. These systems are managed by the sewerage undertaker and accept the flows from the smaller private drains. In this area that Company is Thames Water Utilities Limited.

Surcharge - When sewage cannot be contained within the piped system then the excess flows will escape (surcharge) through the lowest or weakest point upstream of the restriction, usually an inspection chamber.

Responsibilities for drains and sewers

In the Borough of Surrey Heath, the responsibility for maintaining most of the sewers and lateral drains lies with Thames Water Utilities Ltd. Accordingly any problems encountered with your lateral drains beyond the curtilage of your home and any connecting sewers should in the first instance be reported to them by telephoning 0800 316 9800. (This is regardless of who you pay your water bills to).

Thames Water should dispatch a drainage engineer to inspect the system and ascertain the cause of the problem. If the blockage or defect is located in the public sewer system they will arrange for its clearance or repair without further cost to the enquirer. If however they discover that the problem is not connected with their system and it is either part of a private drain or sewer system they will refer it back to the owners. They may offer to clear or repair the defects but please be aware they can then charge for this work.