Glossary of Drainage Terms

Whether you're a DIY type of person handling a home project, or a pro in the field, drainage terms can be a bit of a puzzle. That's where this glossary comes in handy. We've broken down the complex world of drains, sewers, and water management into bite-sized, easy-to-understand definitions.

From common terms you might hear every day to the technical stuff that makes the experts scratch their heads, we've got it all covered. So, next time someone starts talking about 'culverts' or 'hydro-jetting', you'll be ready to jump right in. Simplify drainage concepts with our expert guide.

A

Activated Sludge Process: Biological wastewater treatment using microorganisms to break down organic matter.

Adoption of Sewers: Transferring sewer system maintenance responsibility to a designated undertaker.

Aeration: Introducing air into wastewater to promote aerobic bacterial growth and pollutant breakdown.

Aesthetic Pollution: Visible sewage materials with minimal environmental impact but causing public concern.

Anaerobic Digestion: Microorganism breakdown of biodegradable material without oxygen producing biogas and reducing sludge volume.

Anti Flooding Device: Installation in sewers preventing backflow to properties during high flow events.

B

Backflow: Undesirable flow reversal in plumbing potentially contaminating potable water with wastewater.

Biofilm: Bacterial film on pipe surfaces potentially causing blockages and flow reduction.

Brownfield Site: Previously developed land with potential contamination considered for redevelopment.

C

Catchment Area: Geographical region from which water drains into a specific waterway or sewer system.

Cavitation: Formation and implosion of air bubbles in fast moving water damaging pipes and pumps.

CCTV Survey: Remote camera inspection of drains and sewers to identify structural issues or blockages.

Collection System: Network of pipes transporting stormwater and wastewater to treatment facilities.

Combined Network: Sewer system collecting both foul water and rainfall runoff in a single pipe network.

Combined Sewer Overflow: Relief structure allowing excess flow discharge during heavy rainfall.

Contributing Area: Specific catchment directly feeding runoff into a particular sewerage system section.

Control Structure: Hydraulic device regulating flow rates in drainage systems.

Culvert: Covered channel allowing water flow under roads or similar obstructions.

D

Depression Storage: Natural surface depressions filled before runoff occurs affecting drainage timing.

Detention Basin: Facility temporarily storing runoff for controlled release preventing downstream flooding.

Detention Tanks: Structures in sewerage systems storing excess water during peak flows.

Discharge: Liquid volume flowing through a conduit section per time unit.

Domestic Wastewater: Household originated wastewater requiring treatment before safe disposal.

Drain: Underground pipeline carrying surface or wastewater to sewers.

Drainage: System of channels and pipes removing stormwater from built environments.

Drain Lining: Trenchless repair method inserting a hardening resin liner into damaged drains.

Drain Tracing: Inspection method locating blockages and concealed drainage features.

Dry Weather Flow: Baseline drainage system flow during periods without rainfall.

E

Effluent: Treated or untreated wastewater flowing from treatment plants or industrial outfalls.

Erosion: Wearing away of soil or sediment by water, wind or other forces.

Erosion Control: Measures preventing or reducing soil wear by natural forces.

Evaporation: Water transition from liquid to gas affecting ground surface drying.

Event: Single rainfall occurrence defined by duration and intensity.

Extreme Event: Infrequent occurrence like large storms or long droughts testing infrastructure limits.

F

Flap Gate: Unidirectional gate preventing backflow while allowing water release.

Foul Sewage: Wastewater from domestic commercial or industrial sources excluding rainwater.

Foul System: Sewerage network specifically designed for foul sewage.

French Drain: Perforated pipe surrounded by gravel redirecting surface and groundwater.

G

Gradient: Pipe inclination angle influencing flow velocity and transport capacity.

Gravity System: Sewerage network relying on gravity for water or sewage movement.

Grease Trap: Device intercepting greases and solids before wastewater system entry.

Greywater: Domestic wastewater excluding toilet waste potentially reusable after treatment.

Groundwater Recharge: Water movement from surface to groundwater maintaining aquifer levels.

Gully: Structure allowing surface runoff entry into sewerage systems while trapping debris.

H

Head Discharge Relationship: Correlation between water level and discharge rate in hydraulic systems.

Highway: Any road or path requiring specific drainage considerations.

Highway Drainage System: Specialised network removing excess surface water from roads.

Hydraulic Capacity: Maximum water volume a pipe or channel can carry based on its characteristics.

Hydraulic Gradient: Water surface or pressure head slope indicating flow direction and rate.

Hydraulic Simulation: Computational analysis of drainage system behaviour under various conditions.

Hydro jetting: High pressure water cleaning method for pipes and sewers.

I

Impermeable Surface: Surface resisting water penetration increasing surface runoff.

Infiltration: Water movement from ground surface into soil.

Inflow: Water introduction into sewerage systems from various sources.

Inlet: Structure allowing water entry into drainage systems often designed to trap debris.

Inspection Chamber: Access point for remote equipment servicing of sewers or drains.

Invert: Lowest internal point of a pipe or channel cross section.

L

Lateral Connection: Sewer service portion extending from main line to property boundary.

Lateral Drains: Private sewers carrying wastewater from properties to public sewers.

Leachate: Liquid passing through waste material often requiring special treatment.

M

Manhole: Structure providing personnel access to sewers for maintenance.

Microtunneling: Trenchless pipeline installation method minimising surface disruption.

Misconnection: Improper drain or inlet connection to unsuitable sewer systems.

Model: Mathematical representation simulating drainage system behaviour.

N

Network: Interconnected system of pipes and structures forming drainage infrastructure.

Non-Return Valve: Device allowing unidirectional flow preventing backflow.

O

Orifice: Pipeline constriction controlling flow rate.

Overflow: Sewage discharge into environment before full treatment.

Overflow Weir: Structure releasing excess water from full capacity systems.

P

Permeable Paving: Paving material allowing water passage reducing surface runoff.

Pervious Surface: Ground surface allowing water infiltration.

Pipe Relining: Trenchless repair method installing new liner within existing pipes.

Primary Treatment: Initial wastewater treatment stage separating solids from water.

Private Sewer: Sewer owned and maintained by property owners served.

Public Sewer: Sewer maintained by public authorities serving multiple properties.

R

Rain gauge: Device measuring and recording rainfall at specific locations.

Rainwater Harvesting: Collection and storage of rainwater for onsite reuse.

Reservoir Storage: Temporary water storage in system components during high flow events.

Root Ingress: Tree root penetration into pipes causing blockages or damage.

Runoff: Water flowing over ground surfaces eventually entering sewers or drains.

S

Screen: Device removing floating solids from wastewater.

Scum board: Submerged plate retaining floating debris in treatment facilities.

Sediment Transport: Movement of solid particles by water flow.

Self-Cleansing Velocity: Minimum flow speed preventing solid settling in pipes.

Separate System: Drainage network with distinct surface water and wastewater pipelines.

Septic Tank: Underground container collecting and partially treating sewage.

Sewage: Water carried wastes from various sources entering sewer systems.

Sewer: Pipe carrying sewage and/or surface water to treatment or disposal points.

Sewer Flooding: Unintended wastewater escape from sewerage systems.

Sewerage: Complete system for sewage collection transport and treatment.

Sewerage System: Network collecting and conveying wastewater to treatment facilities.

Silt: Fine sediment carried by water potentially accumulating in pipes.

Sluice Gate: Sliding gate controlling water flow in channels or pipes.

Soakaway: Subsurface structure allowing water seepage into surrounding soil.

Soffit: Highest internal point of pipe or culvert cross section.

Source Control: Techniques reducing pollutants and runoff at their origin.

Storm Tanks: Containers temporarily holding high stormwater volumes in treatment works.

Sub catchment: Smaller drainage area within larger catchment corresponding to specific inlets.

Surface Wash off: Rainfall runoff carrying surface pollutants into drainage systems.

Surface Water System: Network specifically managing surface water runoff.

Suspended Solids: Solid particles remaining suspended in water or wastewater.

Sustainable Drainage Systems: Approach managing surface water emphasising natural processes.

T

Time of Entry: Duration for surface runoff to enter pipe systems.

Trenchless Technology: Underground utility installation methods minimising surface excavation.

U

Urban Drainage: Pipe systems managing water in built up environments.

W

Wastewater: Used water discharged to drains.

Water Quality: Chemical physical and biological water properties determining its suitability.

Water UK: Organisation representing British water supply companies.

Watercourse: Natural or artificial channel for water passage.

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