Soil, Drain & Rainwater Glossary


Soil, Drain & Rainwater Glossary



Air Admittance Stack: Valve that allows air to enter the system but not to escape in order to limit pressure fluctuations within the sanitary pipework.


Black Water: Waste water containing faecal matter or urine
Branch Discharge Pipe: Pipe connecting sanitary appliances to a discharge stack or drain
Branch Ventilating Pipe: Ventilating pipe connected to a branch discharge pipe.
Bar (accidental static water pressure): Measurement of pressure, 1 bar is approximately equal to 14.7psi. Accidental refers to - If a blockage in the pipe system occurs


Combined System: A drainage system for both rain and waste water in a single pipe
Connection Bend: First fitting in direction of flow after trap outlet.
Cast Iron: Alloy of cast iron and carbon in which graphite can be present in different forms.



Domestic Water: Water which is contaminated by use and normally discharged from WC, shower, bath, bidet, wash basin, sink, floor gully.

Drainage SystemA system composed of drainage equipment, and other components collecting waste water and Discharging by means of gravity; effluent lifting plant may be part of a gravity drainage System.
Discharge StackMain (generally vertical) pipe, conveying discharge from sanitary appliances
Drain: Near horizontal pipe suspended within a building or buried in the ground to which stacks or ground floor appliances are connected.
Domestic Sanitary Appliances: Fixed appliances supplied with water and used cleaning or washing. For example: baths, showers, wash basins, bidets, WCs, urinals, sinks, dishwashers, washing machines.
Depth of Water Seal: The depth of water which would have to be removed from a fully charged rap before gases and odours at atmospheric pressure could pass through the trap.


External Diameter: Mean external diameter of the pipe barrel at any cross-section

Electrical ContinuityIn situations where equip potential bonding (eathring) is requiredThe earthing of the pipe system.


Flood Level: The maximum level to which waste water can rise in a drainage system

Floor GullyDischarge fitting intended to receive water from floors either through apertures in a grating or from pipes connected to the body of the gully. A gully may include a trap.



Grey Water: Waste water not containing faecal matter or urine



Internal Diameter (ID)Mean internal diameter of the pipe barrel at any cross-section.



Minimum Internal Diameter: Smallest internal diameter allowed with maximum tolerance



Nominal Diameter (dn or dia)Numerical designation of size which is a convenient round number approximately equal to the Diameter in mm
Non-Domestic Sanitary AppliancesSpecial sanitary appliances used in commercial kitchens, laundries, laboratories, hospitals, hotels, swimming pools etc.


Rain WaterWater resulting from natural precipitation that has not been deliberately contaminated.
RestrainedPipework (pipes and fittings) prevented from moving eg. Bracketed - In areas particular where high internal pressures could occur eg rainwater systems


Separate SystemA drainage system for draining rain and waste water separately by dedicated pipework.
Sanitary PipeworkArrangement of discharge pipework , with or without ventilating pipes, connected to a Drainage system
Square EntryEqual branch junction that is more than 45deg, or has a centre line radius less than the internal pipe diameter
Swept EntryEqual branch junction that is 45deg or less, or has a centre line radius not less than the internal pipe diameter
Stack OffsetNon-vertical part of a discharge stack
Stack VentExtension of a vertical discharge pipe above the highest branch discharge pipe connection that terminates in an end, open to the atmosphere
SewerSystems of pipes designed to collect waste water and rainwater from buildings and surface water and to convey them to the point of disposal or treatment.



Trade EffulentWater after industrial use and processes contaminated/polluted water including cooling water
TrapDevice that prevents the passage of foul air by means of water seal.



Ventilating PipePipe provided to limit pressure fluctuations within the discharge pipe system
Ventilating StackMain vertical ventilating pipe, connected to a discharge stack, to limit pressure fluctuations within the discharge stack.


Waste WaterWater which is contaminated by use and all water discharging into the drainage system, e.g. domestic and trade effluent, condensate water and also rainwater when discharged in a water drainage system.