Glossary of drainage terminology
At ASL Limited we like to give our customers as much information as possible so that they can make informed decisions about your drainage choices. This glossary of drainage & private sewage system terminology could go a long way toward helping you do that.
Aerobic bacteria. Aerobic organisms or aerobes are organisms that can survive and grow in an oxygenated environment.
Anaerobic bacteria. Anaerobic organisms or anaerobes are organisms that cannot survive and grow in the presence of oxygen. Breakdown:
1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest.
2: Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest.
3: Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration.
4: Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube but not the very top.
5: Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes, however, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.
Bacteria. The microorganisms that eat the effluent from within your treatment plant cleaning the wastewater as it passes through.
Binding rules. A set of standards specified by the Government to ensure environmental protection from your private sewage system (also known as ‘General Binding Rules’).
Blocked drain. A blockage in your sewage drain, surface water drain, or your drainage field/land drains.
CCTV. We use ‘closed-circuit television’ in our drain surveys and drain mapping to check the pipework condition and see what is blocking drains.
Cesspit/Cesspool. A cesspit is a sealed container in the ground that collects sewage and wastewater from your property. It has to be emptied regularly. It should not discharge to land drains unless you have a permit to do so. You can find out more about cesspits in our blog entitled ‘What is a cesspit?’
Channel drain. A grid covered drain in the ground often along a curbside in the road or in front of your garage. Also called ‘Aco channels’ (Aco is a brand name) or slot channels.
Clinker. Porous stone allows bacteria to live on its surface, making it a good material for filtering wastewater or sewage water.
Clinker Bed. A bed dug out of the ground and filled with ‘clinker’ stone to filter wastewater or sewage through. (Usually found in older systems and worth checking with the Environment Agency if a permit is required or an upgrade is needed.)
De-watering. The removal of groundwater or surface water from a site or excavation.
Discharging. The final step of a septic tank or treatment plant. The liquid leaves a septic tank or treatment plant and filters into the ground via a drainage field or surface water from a treatment plant.
Drains/drainage. Many people don’t realise that there are two drainage systems within their properties: foul water and surface water.
- Surface Water. Surface water drainage includes rainwater and runoff from driveways, roofs, gutters, and pond overflows. This water can be safely returned to watercourses untreated. Often discharges to a soakaway, but can be connected to a surface water sewer. In some areas, surface water and foul water discharge to a combined sewer.
- Foul water; sewage water, wastewater. In comparison, foul water is any wastewater from bathrooms, toilets, kitchens and washing machines. Untreated sewage water must never be discharged into a watercourse because there is an unacceptable risk; you may pollute nearby rivers and even drinking water, so it’s crucial to avoid this. Foul water, including kitchen waste, should not be connected to the surface water system.
Drainage field. Series of perforated pipework underground that allows treated wastewater to drain into the ground for further treatment. Sometimes referred to as ‘land drains’, a drainage field for sewage is a particular type of land drainage that follows specific rules. Also, see ‘Land drains’.
Effluent. A term given to wastewater from your home.
Foul Water (sewage water, wastewater). Foul water is any wastewater from bathrooms, toilets, kitchens and washing machines. Untreated sewage water must never be discharged into a watercourse because there is an unacceptable risk; you may pollute nearby rivers and even drinking water, so it’s crucial to avoid this.
General binding rules. A set of standards specified by the Government to ensure environmental protection from your private sewage system (also known as ‘Binding Rules’).
Gully. A grid covered drain in the ground often along a curbside in the road, in your driveway/patio (surface water) or outside of your kitchen (foul water).
Grease trap. A kind of filter unit that will catch a lot of the grease, fat and oils from washing up and kitchen waste that is inadvertently put down your sink. Often a requirement for restaurants. Larger applications may have an underground tank outside the building.
High-pressure water jetting. A cleaning method used to clear blocked drains using high-pressure water jet equipment. Also used to clean drains of fats/grease/debris and with additional attachments can remove roots from the drain.
House purchase survey. A survey of all the drains in and around a property you may be buying or selling. This is not typically included in a ‘Homebuyer Survey’ purchased through your estate agent. If the property has a private sewage system, this should also be inspected for a condition report and to check it meets current regulations. See also ‘General Binding Rules’ and ‘Tank Inspections’.
Interceptor. A type of trap in your drain, before your drain connects to the main sewer, originally installed to prevent smells coming back into your house. Also, see ‘petrol interceptor’.
Jetting. A cleaning method used to clear blocked drains using high-pressure water jet equipment. Also known as ‘High-Pressure Water Jetting’.
Land drains. An umbrella term used to describe various types of drainage system. Land drains are often used to tackle surface water drainage issues. Other terms include herringbone drainage, french drains and field drains. A drainage field for foul wastewater is also a type of land drainage.
Main drain connection. The joining of your private drainage system with the public drains.
Main sewer. The public sewer network owned and maintained by the local water authority. See also ‘Public sewer’.
Microorganisms. The bacteria that eat the waste from your household sewage water as it runs through a treatment plant.
Moling. Underground tunnelling that allows the insertion of pipework or ducting without digging trenches. A pit will still need to be excavated every 10m or so and at each change of direction.
Non-return valve. A device used to prevent water from flowing back the way it came. Can be used in underground drainage and also used on pumped systems. Can also be used to prevent rodents from travelling up the pipework.
Operator. The term used to describe the person responsible for a private sewage system. The Operator is the person who:
- owns the property that uses the private sewage system.
- owns a property that shares the system with other properties - each property owner is an operator.
- has a written agreement with the property owner that states you are responsible for the system’s maintenance (e.g. you’re renting and it’s in your tenancy agreement).
Percolation. The rate at which water filters through the soil indicating how permeable the ground is. This will determine the suitability of the ground for a soakaway or drainage field.
Petrol Interceptor. A trap or catch pit found in car parks, fire stations, garages, and petrol station forecourts to catch runoff of petrol and debris and separate the petrol from the surface water.
Private sewage system. A system to dispose of wastewater from your property if you are not connected to the main public sewer. Includes septic tanks, treatment plants and cesspits/cesspools. You can find out more about ‘private sewage systems’ on our webpage ‘private sewage systems’.
Public sewer. The public sewer network owned and maintained by the local water authority. See also ‘Main sewer’. A sewer is deemed to be public at the point it becomes shared between two properties. (Some exclusions apply for newer developments and private roads.) For more information, see our blog post on drainage responsibility.
Pump. A pump can be used for surface water or foul water where the natural gradient of the drains is not sufficient to reach the discharge point. Usually housed within a pumping station.
Pumping station. The enclosure that houses your pumps. Usually an underground tank with a metal cover for access. Also called a pump chamber.
Re-rounding. A repair method for pitch fibre pipes that involves pulling a round metal head through the pipework to restore its shape. A structural liner is then installed to seal the pipework.
Retention time. The time it takes for solids to separate from the wastewater and how much is retained in the holding tank.
Septic tank. Underground container/tank system that collects sewage and wastewater from your property and enables settlement to occur. A septic tank will have a minimum of two chambers and will discharge to a drainage field. Historically, septic tanks were able to discharge to surface water; however, this is no longer allowed. For more information, please see ‘General Binding Rules’. You can find out more about septic tanks in our blog entitled ‘what is a septic tank?’
Sewage water (wastewater, foul water). Sewage or Foul water is any wastewater from bathrooms, toilets, kitchens and washing machines.
Sheet Piling / Shoring. A temporary structure used to prevent the collapse of the surrounding walls of an excavation.
Soakaway. Underground pit aerated with a choice of materials to allow water to drain away at a steady rate. Soakaway is an umbrella term for all types of infiltration systems. Some examples of various types of soakaways are ‘drainage fields’, ‘rubble-filled pits’, ‘crated soakaway systems’ and ‘perforated concrete chambers’.
Surface Water/rainwater. Surface water includes rainwater and runoff from driveways, roofs, gutters and pond overflows. This water can be safely returned to watercourses untreated.
Tank inspections. If a property has a private sewage system, this can be inspected for a condition report and to check it meets current regulations. See also ‘General Binding Rules’ and ‘House purchase survey’.
Treatment. The process by which water is cleaned through various stages of separation and bacteriological action.
Treatment plant. A domestic treatment plant is an underground private sewage system. It treats raw sewage through different stages of separation to a standard that allows it to be discharged into either a drainage field or a flowing watercourse (subject to meeting the binding rules or obtaining a ‘Consent to Discharge’ from the Environment Agency – For more information, please see ‘General Binding Rules’). You can find out more about treatment plants in our blog entitled ‘what is a treatment plant?’
Watermains. The pipework providing the main supply of water into your property.
Wastewater (sewage water, foul water). Wastewater or foul water is any sewage water from bathrooms, toilets, kitchens and washing machines.