Question 1

What is the difference between a sewer and a drain?

Accepted Answer

A drain serves a single property - it runs from the appliances within that property to the point of connection to the sewer or to a private treatment system. A sewer serves more than one property - it is a shared pipe that collects drainage from multiple drains and carries it away to the treatment works or point of disposal. Public sewers are adopted (taken over and maintained) by the water company; private sewers (shared drains serving more than one property but not adopted) are the shared responsibility of all connected owners. Since October 2011, most shared private sewers in England and Wales were automatically adopted by water companies, significantly reducing the number of private sewers.

Question 2

What is the difference between a foul sewer, surface water sewer, and combined sewer?

Accepted Answer

A foul sewer carries only foul water (sewage and grey water) to the sewage treatment works. A surface water sewer carries only rainwater and clean surface runoff, discharging directly to a watercourse without treatment. A combined sewer carries both foul water and surface water together to the treatment works. Combined sewers (common in older urban areas) cause problems during heavy rainfall because the large volume of surface water overloads the treatment works, causing combined sewer overflows (CSOs) - untreated sewage released directly to rivers. The Water Industry wants to separate combined sewers over time; all new developments must use separate foul and surface water drainage.

Question 3

What are the rules on building over or near a public sewer?

Accepted Answer

Building over or near a public sewer requires prior approval from the water company under their Build Over/Near Sewer (BONS) process. Water companies generally: prohibit buildings directly over a sewer larger than 160mm diameter; require a structural assessment and often a concrete encasing or bridging structure for buildings over smaller sewers; require minimum clearances (typically 3m from the centre of a sewer up to 225mm diameter; greater clearances for larger sewers); and require inspection of the sewer by CCTV before and after construction. Failure to obtain approval can result in the water company requiring demolition or significant remediation work at the owner's expense.

Question 4

How do I find out if there is a sewer under my land?

Accepted Answer

Public sewers in England and Wales are recorded on the sewer map maintained by each water company. You can request a copy of the sewer map (called a Section 199 search or drainage search) from the water company or through a solicitor/conveyancer as part of a property search. The sewer map shows the position of public sewers but may not show private drains. For private drains (which serve only your property), records are less reliable - your original building drawings may show drain runs, or a CCTV drain survey can be used to trace drain routes. Drain tracing dye can also be used to confirm which drain routes connect which inspection chambers.

Sewer

Just so you know...