Drainage Glossary
Understanding drainage terminology helps property owners make informed decisions about their drainage systems. This glossary explains common terms used in drainage, sewerage, and wastewater management. Whether you are dealing with a blocked drain, planning a septic tank installation, or preparing for a CCTV survey, these definitions offer clear explanations of the technical terms you may encounter.
A
Adoption Survey
A CCTV drainage survey is carried out to ensure that newly installed drainage systems meet the required standards for adoption by water companies or local authorities. These surveys verify that pipework, connections, and construction conform to regulations such as Sewers for Adoption, allowing the drainage system to be transferred to the relevant authority for ongoing maintenance.
b
Blockage
An obstruction within a drainage pipe or sewer that prevents wastewater from flowing freely. Blockages can be caused by the build-up of grease, food waste, foreign objects, tree roots, or structural faults such as collapsed pipes. High-pressure jetting and mechanical methods are commonly used to clear blockages and restore normal flow.
British Standards
Technical standards that specify requirements for the design, installation, and maintenance of drainage systems. Relevant standards include BS 6297:2007 for drainage fields, BS EN 12566-3 for small sewage treatment plants, and BS EN ISO 11296-4:2011 for pipe lining systems. Compliance with British Standards ensures that drainage installations meet recognised quality and safety requirements.
Building Regulations
Legal requirements governing the construction and alteration of buildings in England and Wales. Part H of the Building Regulations covers drainage and waste disposal, setting standards for designing and installing drainage systems, including septic tanks, treatment plants, and sewer connections. Approval from Building Regulations is necessary for new drainage installations and major modifications.
c
CCTV
CCTV (Closed Circuit Television) is a closed system made up of video cameras, displays, and data networks that transmit images from cameras to monitors. In drainage, CCTV cameras mounted on remote control units are inserted into pipes to examine internal conditions, locate blockages, and identify structural defects without the need for excavation.
Cess Pit
A cesspit, also called a cesspool, is an underground tank that collects and temporarily holds sewage and wastewater from residential or commercial properties. Unlike a septic tank, which provides partial treatment of wastewater, a cesspit simply acts as a storage vessel without any treatment or disposal systems.
Cesspits are usually made from watertight materials such as concrete, brick, or steel. They are designed to be completely sealed to prevent leaks or seepage of waste into the surrounding soil. When wastewater enters a cesspit, it remains stored within the tank until it is pumped out and disposed of by a professional service provider. The frequency of pumping depends on the capacity of the cesspit and the volume of wastewater from the property.
CIPP Lining
Cured-in-Place Pipe lining is a trenchless repair technique that installs a resin-impregnated liner inside an existing damaged pipe. The liner is inserted, inflated, and cured using hot water, steam, or ultraviolet light to form a new structural pipe within the old one. CIPP offers a durable repair with a lifespan of up to 50 years, reducing the need for excavation and surface reinstatement.
Collapsed Pipe
A section of drainage pipe that has suffered structural failure, causing the pipe walls to cave in and block the flow of wastewater. Collapse can result from age, ground movement, heavy loading, corrosion, or root damage. CCTV surveys identify collapsed sections, which typically require either excavation and replacement or trenchless repair methods, depending on the severity and location.
Combi Units
Smaller drainage vehicles, usually with a 7.5-tonne capacity, combine high-pressure jetting and vacuum extraction capabilities. Combi units are designed for clearing blockages and cleaning smaller-diameter pipework in areas with limited space or difficult access, making them ideal for domestic and urban drainage tasks.
Confined Space
A confined space is any enclosed or partly enclosed area within a drainage system that has limited entry or exit points. Examples include deep manholes, underground storage tanks, sewers, culverts, and pump chambers. These spaces pose hazards such as poor ventilation, accumulation of toxic gases, oxygen deficiency, or risk of flooding. Working in confined spaces requires trained personnel, comprehensive risk assessments, atmospheric monitoring, ventilation equipment, and emergency rescue procedures.
Culvert
A structure that allows water to flow beneath roads, railways, or embankments. Culverts are usually made from concrete, steel, or plastic, and they vary from small pipes to large box structures. Regular inspection and cleaning of culverts help prevent blockages that could lead to flooding or structural damage.
d
Desludging
The process of removing accumulated solid waste and sludge from septic tanks, treatment plants, or drainage systems. Regular desludging is vital to maintain system efficiency, prevent blockages, and ensure compliance with environmental regulations. The frequency of desludging depends on tank capacity and usage levels.
Discharge to Ground
The release of treated wastewater into the soil through a drainage field or soakaway system. Under the General Binding Rules, properties can discharge up to 2 cubic metres per day into the ground using either a septic tank or small sewage treatment plant. The drainage field enables natural filtration and treatment as wastewater percolates through the soil.
Discharge to Surface Water
The release of treated wastewater into rivers, streams, ditches, or other watercourses. Properties can discharge up to 5 cubic metres per day into surface water, but only using a small sewage treatment plant that meets British Standards, not a septic tank. Stricter regulations apply to surface water discharges to protect water quality and prevent pollution.
Displaced Joints
Pipe joints that have shifted out of alignment due to ground movement, settlement, or structural deterioration. Displaced joints create gaps or misalignments in the pipe run, allowing soil infiltration, leading to blockages and reducing flow capacity. CCTV surveys identify displaced joints, which can often be repaired using patch lining techniques.
Drain Interceptor
A drain interceptor, also called a grease trap or oil interceptor, is a device used in plumbing systems to separate and trap substances like grease, oils, fats, and solids from wastewater before it enters the drainage system. It is essential in preventing these substances from causing blockages and pollution in sewer lines and the environment. The purpose of a drain interceptor is to catch and collect the heavier substances in wastewater that can solidify or cause build-ups over time. It usually consists of a chamber or tank installed in the drainage line, often near sinks, dishwashers, or other areas where grease and oils are present.
Drainage Field
A subsurface wastewater disposal system, also known as an infiltration system or leach field, comprises a series of perforated pipes laid in trenches filled with gravel. Treated effluent from septic tanks or treatment plants disperses through the drainage field, where it undergoes further natural treatment as it percolates through the soil. Drainage fields must be designed and constructed to British Standard BS 6297:2007 and sized appropriately for the property’s wastewater volume.
E
Environment Agency
The government body responsible for protecting and enhancing the environment in England. The Environment Agency regulates small sewage discharges through the General Binding Rules, issues environmental permits, monitors water quality, and enforces compliance with environmental legislation, including the Water Industry Act 1991 and the Environmental Protection Act 1990.
Environmental Protection Act 1990
Legislation that provides the framework for waste management and pollution control in England and Wales. The Act includes duty of care requirements for waste handling, disposal, and transfer, ensuring that drainage waste is collected, transported, and disposed of safely at licensed facilities. All waste tankering services must follow this legislation.
f
Foul Sewer
A drainage pipe or system designed specifically to carry wastewater from toilets, sinks, baths, and other domestic or commercial sanitary fixtures. Foul sewers transport sewage to treatment plants or septic systems, keeping it separate from surface water drainage to prevent contamination and enable proper treatment.
G
General Binding Rules
Environmental regulations introduced on 1 January 2015 govern small sewage discharges from septic tanks and treatment plants in England. The General Binding Rules set conditions under which operators can discharge wastewater to ground or surface water without needing an environmental permit. These rules cover discharge volumes, system standards, maintenance requirements, and restrictions on discharges near public sewers or in sensitive areas.
Gully
A ground-level drainage grate and chamber collect surface water from roads, driveways, car parks, or other paved areas. Gullies connect to the surface water drainage system and include a trap to prevent debris and odours from entering the main network. Regular cleaning helps prevent blockages and keeps the drainage system functioning effectively.
H
High-Pressure Jetting
A drainage cleaning method that utilises powerful water jets to break up blockages, remove debris, and scour pipe walls. Water is delivered through specialised nozzles at pressures sufficient to dislodge stubborn deposits, including grease, scale, roots, and concrete. High-pressure jetting is effective for pipes of various diameters and can be adjusted for different materials and blockage types.
Homebuyer Survey
A pre-purchase drainage survey is performed before buying a property to assess the condition of underground drainage system’s condition. These surveys usually use CCTV camera inspections to examine pipes and detect existing issues such as blockages, cracks, root intrusion, or collapsed pipes. Homebuyer surveys help buyers make informed choices, negotiate repairs, or adjust the purchase price accordingly. Building societies and mortgage lenders often require these surveys for older properties or areas with known drainage problems.
I
Infiltration
The unwanted entry of groundwater or surface water into drainage pipes and sewers through cracks, displaced joints, or damaged connections. Infiltration increases flow volumes, reduces system capacity, and can cause flooding during heavy rainfall. CCTV surveys identify infiltration points, which are typically repaired using patch lining or pipe replacement.
j
Jet Vac Units
Advanced waste tankers combine high-pressure water jetting with powerful vacuum extraction to clean and clear drainage systems. Jet Vac units deliver water through specialised nozzles to break up blockages and debris, while simultaneously using vacuum suction to remove material and transport it to onboard storage tanks. These versatile vehicles range from compact 7.5-tonne combi units to large high-capacity tankers capable of lifting waste vertically up to 26 metres.
M
Mains Sewer
A public sewer owned and maintained by the local water authority that collects wastewater from multiple properties and transports it to treatment facilities. Properties connected to mains sewers benefit from centralised wastewater treatment and do not need private on-site systems. Connection to the mains sewer is the standard solution for properties in urban and suburban areas where public sewerage infrastructure is available.
Manhole
An access point in a drainage system, also called an inspection chamber, that allows engineers to enter, inspect, and maintain underground pipes and sewers. Manholes are usually made from concrete, brick, or plastic and are placed at junctions, changes in direction, or at regular intervals along pipe runs to enable inspection and cleaning.
MSCC5
The Manual of Sewer Condition Classification, Edition 5, offers standardised codes for recording defects and conditions observed during CCTV drainage surveys. MSCC5 grading ensures consistent reporting and allows accurate assessment of drainage system condition for maintenance planning, adoption, and compliance purposes.
N
NRSWA
The New Roads and Street Works Act 1991 outlines regulations for carrying out works on public highways, including drainage repairs and installations. A NRSWA Supervisor qualification is necessary for personnel managing street works to ensure effective traffic management, safety procedures, and reinstatement standards are upheld during highway drainage projects.
O
Open Cut Excavation
Traditional drainage repair method involving excavation of the ground to access and replace damaged pipes. Open cut excavation is employed when trenchless methods are unsuitable due to extensive damage, collapsed sections, or the need to upgrade pipe diameter. After the repair, the excavation is backfilled and the surface reinstated to its original condition.
P
Patch Lining
A localised trenchless repair method that uses glass fibre and epoxy resin to seal specific defects such as cracks, fractures, or displaced joints. The patch is placed over the damaged area and cured in situ, restoring pipe integrity without excavation. Patch lining is cost-effective for isolated defects and can be completed quickly with minimal disruption.
Pipe Bursting
A trenchless pipe replacement method that breaks apart the existing damaged pipe while simultaneously pulling a new pipe into position. Pipe bursting is used when pipes are severely damaged or require upsizing, offering complete replacement without extensive excavation. The method is suitable for various pipe materials and diameters.
Pump Station
A facility containing pumps and associated equipment that lifts wastewater from low-lying areas to higher points, allowing it to flow by gravity to treatment plants or outfalls. Pump stations are essential where natural slopes are inadequate for gravity drainage and need regular maintenance to function properly.
R
Root Ingress
The intrusion of tree or plant roots into drainage pipes through cracks, joints, or defects. Roots seek moisture and nutrients within pipes, leading to blockages and structural damage as they grow. High-pressure jetting with specialised cutting nozzles removes root intrusions, but permanent solutions may involve pipe lining or replacement to seal entry points.
S
S104 Agreement
A legal agreement under Section 104 of the Water Industry Act 1991 between a developer and a water company for the adoption of sewers serving new developments. S104 agreements specify construction standards, inspection requirements, and maintenance periods before the water company assumes responsibility for the drainage infrastructure.
Scale
Hard mineral deposits that form on pipe walls, usually made up of calcium, lime, and other minerals found in water. Scale accumulation decreases pipe diameter, hampers flow, and may cause blockages. Descaling with high-pressure jetting removes these deposits and restores the pipe’s full capacity.
Septic Tank
A septic tank is an underground wastewater treatment system often used in areas lacking access to a mains sewer system. It is designed to collect, treat, and dispose of household wastewater on site. Proper maintenance and regular pumping of the septic tank are vital to ensure its efficient operation. Over time, the sludge and scum layers build up and must be professionally removed to prevent blockages, system failure, and environmental contamination.
Sewers for Adoption
The national specification for the construction of sewers and lateral drains to be adopted by water companies under Section 104 agreements. Sewers for Adoption details the design standards, materials requirements, construction methods, and inspection procedures that must be followed for drainage systems serving new developments.
Silt
Fine sediment particles that settle in drainage pipes and decrease flow capacity. Silt build-up occurs from soil infiltration, surface water runoff, or inadequate gradients. Regular cleaning with Jet Vac equipment removes silt and prevents blockages.
Soakaway
A soakaway, also known as a soak pit or infiltration trench, is a drainage system designed to manage surface water runoff. It is commonly used to control and disperse excess rainwater or wastewater from buildings, driveways, or other impermeable surfaces.
Source Protection Zone
Areas designated by the Environment Agency where groundwater sources used for public drinking water supplies are safeguarded against pollution. Source Protection Zone 1 (SPZ1) represents the innermost zone with the highest level of protection. Septic tank discharges within SPZ1 require an environmental permit from the Environment Agency, and additional conditions are imposed to prevent groundwater contamination.
Surface Water
Rainwater runoff from roofs, roads, driveways, and other impermeable surfaces is collected by gullies and drains. Surface water drainage systems are typically separate from foul sewers to prevent overwhelming treatment facilities during heavy rainfall and to allow direct discharge to watercourses where appropriate.
T
Tankering
The collection, transportation, and disposal of liquid waste using specialist vacuum tanker vehicles. Tankering services extract waste from septic tanks, cesspits, grease traps, and other drainage systems, transporting it to licensed treatment facilities in line with environmental regulations and duty of care requirements.
Treatment Plant
A sewage treatment plant, also known as a package treatment plant, uses mechanical and biological processes to treat household wastewater to a higher standard than septic tanks. These treatment plants produce cleaner effluent suitable for discharge into surface water under the General Binding Rules, provided they comply with British Standard BS EN 12566-3 and adhere to regular maintenance requirements.
Trenchless Repair
Drainage repair methods that restore pipe function without excavation, also known as no-dig repairs. Trenchless techniques include CIPP lining, patch lining, and pipe bursting. These methods reduce costs, minimise surface disruption, and enable faster completion compared to traditional open-cut excavation.
U
UV Lining
A CIPP lining method that uses ultraviolet light to cure resin-impregnated liners, offering faster installation than traditional hot water or steam curing. UV lining employs light-reactive vinyl ester resins that produce no vapour or odours, enabling rapid curing speeds of up to 1.3 metres per minute and reducing site disruption.
V
Vacuum Extraction
The suction process used by Jet Vac units to remove debris, water, and waste material from drainage systems. Vacuum extraction works alongside high-pressure jetting to ensure thorough cleaning, with material extracted at the source and stored in onboard tanks for disposal at licensed facilities. Modern Jet Vac equipment can lift material vertically up to 26 metres.
W
Water Industry Act 1991
Primary legislation that governs water and sewerage services in England and Wales. The Act establishes the framework for sewer adoption, drainage standards, environmental protection, and the responsibilities of water companies. All drainage construction, repair, and discharge activities must comply with the Water Industry Act 1991.
Drainage Services Across the South West
For expert drainage services throughout Devon, Cornwall, Somerset, and Dorset, Exjet offers comprehensive solutions including CCTV surveys, high-pressure jetting, septic tank services, and civil engineering works. Our skilled engineers can assist with any drainage problem, from emergency blockages to planned maintenance and system installations.