Glossary of Terms

Backdrop

Generally a vertical section of pipe to take a high level connection into a manhole or inspection chamber down to the invert level of that chamber. The backdrop is usually outside the manhole or chamber but can sometimes be found inside. Backdrops prevent long runs of steep pipework which can cause excessive velocities and discharge rates.

The use of concrete formed in the base of a chamber or a large pipe/culvert to provide a good manner of directing flows in the correct direction and maintaining self-cleansing velocities, especially useful for areas that are subject to surcharge or heavy flows.

Biscuit

Alternative name for cover slab over concrete chamber or manhole .

CCTV

Closed circuit television, a system to provide pictures and/or video inside a pipe using a remote camera.

Combined Drain or Sewer

Sewer or drain that contains both foul water and surface water .

Stepped Brickwork that is used to connect the top of the chamber to the cover frame, usually where the cover frame is smaller than the chamber dimensions.

Cover Level

Ground level or level on the cover of a manhole or inspection chamber .

CSO

Combined Sewer Overflow, generally a chamber or structure on a combined sewer designed to divert or overflow excess flow during storm events into a nearby watercourse. Under low flows in dry weather when the flow is predominantly foul water only the flow passes through and onto the treatment works .

Discharge Rate

The flow rate of a liquid, generally measured in litres per second (l/s), within a pipe or channel.

A ductile iron chamber cover that is two triangular shaped pieces bolted together.

Used for some pipe systems, manhole covers, gully gratings etc.

Foul Water Drain or Sewer

Drain or sewer which has only connections from foul water appliances (WCs, sinks, hand basins, baths, washing machines etc).

Inspection Chamber

A smaller version of a manhole intended for access to the drain or sewer only from ground or surface level.

Invert Level

The lowest internal level of a pipe, culvert or channel.

Mobile high power water jet equipment for clearing sewer / drain blockages.

Manhole

A brick built or concrete chamber on a drain or sewer to allow man-entry for cleaning, rodding, inspection and removal of debris from the system.

Reinforced steel bar, a framework system that is used with concrete works to provide additional support.

A length of pressure pipe (pipe suitable material capable of withstanding internal pressure) from a pump or pumping station used to carry effluent under pressure to the point of discharge.

Access point at the head of a pipe to allow rodding or access downstream.

Soffit Level

The highest internal level of a pipe or culvert.

Steps or rails built into the inner wall of a chamber or manhole at preset intervals for access.

SuDS

Sustainable Drainage System (used to be referred to as Sustainable Urban Drainage Systems). A sequence of control structures designed to drain surface water in a more sustainable fashion than some conventional techniques.

A term used to describe a chamber or pipe that is flooded.

Surface Water Drain or Sewer

Sometimes referred to as Stormwater, drains only surface water (rainwater) from roofs and paved areas.

Treatment Works

Building or plant designed to treat incoming sewerage.

A form of pumping station that uses submerged pumps to move effluent to the treatment works or similar area.

Abbreviations

GK - Grit King® Separator

TM - Trade Mark

STW - Sewage Treatment Works

WwTW - Wastewater Treatment Works

WTW - Water Treatment Works

CDM - Construction Design Management

Drawing Abbreviations

TWL - Top Water Level

AOD - Above Ordinance Datum

CL - Centre Line

TP - Termination Point

EGL - Existing Ground Level

P&ID - Process and Instrument Drawing

PS - Pressure Switch

FS - Flow Switch

SOV - Solenoid Valve

V - Valve

PRV - Pressure Reducing Valve

CRS - Centres