Glossary of Basic Plumbing Terms

by Chelsea Oliver 7th February 2017

united kingdom glossary of basic plumbing terms


When it comes to plumbing, understanding the terms of the trade can be handy, whether you’re requesting a service appointment or going the DIY route. Here, we’ll cover the most basic phrases and jargon to get you started.




Acrylonitrile butadiene styrene. ABS (plastic) pipe is used for drainage and venting.



A fitting that joins threaded and non-threaded pipe ends, or two different types of pipe together.




Air trapped in pipes that causes a reduction or complete stop in water flow.




A thermostat that is submerged in water.


Back Flow


Occurs when unwanted water from one system backs into any part of the main distribution system. Backflow is a serious risk for contamination, particularly of potable water.


Back Flow Preventer


A device that stops back flow. Commonly used to protect potable water from contamination.




When the flow of liquid is reversed and siphons back towards the source. This can cause contamination.


Backwater Valve


A sewer line valve that prevents sewage from flowing back into the property.


Ball Check Valve


A valve that uses a ball to seal against a seat, stopping the flow of water in one direction.




A fill valve that controls the flow of water from the water supply line into a gravity-operated toilet tank.




The unit that water pressure is measured in.




Handicap accessible, such as a shower enclosure with a wheelchair opening and minimal bottom track.


Bleed Valve


A valve that releases air from a central heating system.




A hot water tank that heats water, turning it into steam. Often used as a power source for radiators and hot water systems. Types include combi, conventional and system.


Butterfly Valve


A serviceable valve that allows water to flow through it when open. When closed, it stops the flow.


Catch Basin


Collects and traps debris in storm drains and sewer systems, preventing it from entering drainage pipes, streams and lakes.


Check Stop


A shut-off valve used with tub or shower faucet. It is activated by turning a slotted stem with a screwdriver, also referred to as a service or screwdriver stop.




A tank for storing water, such as for supplying taps or toilets, or housing rainwater.




A fitting access in a venting or drainage system installed to provide access for cleaning and inspection.  


Combi Boiler


The most popular type of boiler in the U.K., combi boilers heat only the water you use. Combi boilers heat water straight from the mains, providing an unlimited supply, and do not require a hot water cylinder or cold water tank.




Tube or duct that houses electrical wiring or cable. Also a pipe or channel for conveying fluids, such as water.


Conventional Boiler


A conventional, or regular, boiler, sends hot water to a radiator and a hot water cylinder. A conventional boiler sends water to taps simultaneously and is best suited to larger homes, particularly those with more than one bathroom.




Rigid and soft copper pipe is most commonly used for hot and cold tap water and as HVAC refrigerant lines. Resistant to corrosion, it is expensive in comparison to some other types of pipe, such as PEX.  




A fitting used to connect two pipes, different couplings (steel, brass, copper, etc) are available for different plumbing systems.




The barrier built into the trapway of a toilet that controls the water level in the bowl.


Drain Valve


A device that allows the drainage of stored contents from a water heater.


Dual Flush Toilet


A high efficiency toilet (HET) that conserves water by offering two different toilet flush volumes – a low volume flush for liquids and a full volume flush for solids.




A Drainage, Waste and Vent system is part of a system that removes waste water (sewage and greywater) from a building. A DWV also regulates air pressure in the system pipes to aid free flow.




Energy Cut Off (ECO) is a safety device designed to cut power to the water heater and prevent high temperature.




Energy Factor (EF) is a measure of the overall efficiency rating of a water heater. This is based on the model’s efficiency, recovery, energy input and more.




A fitting with two openings that changes the direction of the line. Often called “ells,” they are available in 45°, 90° and 22.5°, though the latter is uncommon.


Face Plate


Trim piece located behind a single-control wall-mount faucet handle. Also called a dial plate.




An exposed plumbing fitting used to control the flow of water to a basin, such as a sink.


Feed Pump


A pump that supplies water to a boiler.




Used in pipe systems to connect sections of straight pipe or tubing, as well as to adapt to different sizes or shapes and for purposes such as regulating {or measuring) fluid flow.




A source of discharged water or drain, such as basins, tubs, toilets, faucets and more.




Both the Surrey flange and the York flange fit onto the top of a hot water cylinder and allow the hot water to be drawn away from the tank, without any air. The Essex flange, which fits onto the side of a hot water cylinder, fulfills the same purpose.




The area of floor space taken up by an appliance such as a boiler.





Water that contains less than 1,000 milligrams per litre of dissolved solids. Water containing more than 500mg/l of dissolved solids is undesirable for many uses including drinking.




The process of applying a coating of zinc (via hot dipping or electrolytic deposition) to iron or steel for the benefit of corrosion protection.


Grey Water


Waste water from domestic processes that can often be reused. This includes water from laundry, baths, showers, dish washing and more. Grey water does not come from toilets.


Hard Water


Natural water with high mineral content. It is formed when water percolates through limestone and chalk deposits, which are largely formed of calcium and magnesium carbonates.


Hex Key


Allen wrench.


Immersion Heater


An electric water heater that sits inside of a hot water cylinder. Often used as a backup for combi boilers, immersion heaters are connected to their own power supply.


Indirect Hot Water Cylinder


A hot water cylinder where the water heated by the boiler is fed through a coil of piping inside the cylinder to heat the domestic water. It often includes an electric immersion heater so that the tank can be heated even when the boiler is turned off.




Faucet handles.


Instantaneous Water Heater


A type of water heater that heats the water supply as it passes through - no storage tank necessary. Also referred to as a tankless heater.




A length of pipe.


Junction Box


A utility area where incoming current is connected in an electrical appliance.


Laundry Tub


A large standing basin or deep sink commonly found in a laundry room. Often used for draining washing machines, hand washing clothing and other cleaning.




Loss of fluid, such as through a tap. This is typically due to gasket wear or mechanical breakdown.


Low Consumption Toilet


A type of toilet designed to flush using less than 1.6 gallons of water. Also referred to as a water-saving or low flush toilet.




A form of trap used under fixtures such as basins and baths.




Cross-linked polyethylene. This pipe is commonly used for water supply lines and hydronic radiant floor heating. It is less expensive and faster to install than copper.




Safe to consume, such as for drinking or use in cooking or baking.


Power Shower


A power shower utilizes a device that increases water pressure to create a more powerful spray.


Pressure Assisted Toilet


A toilet that operates using compressed air, which removes more waste products when flushed. Pumps and additional devices are not needed as the air is compressed as water enters the toilet cistern.




Polyvinyl chloride. Commonly used in sewer lines and underground water systems, PVC pipe is known for its durability and also does not rot or rust.




A fitting that connects pipes of different sizes together.




A vertical assembly of pipe and fittings that typically distributes water upward.


Septic Tank


A tank containing waste from a home or building that allows solid matter to settle before being pumped and removed. Typically used in remote locations that are not connected to a sewer system.


Soldering (Solder)


A process in which two or more pipes are joined by melting and putting a metal filler (solder) into the joint.





A valve for turning a home's cold water system on and off. 



System Boiler


A system boiler pumps hot water through a central heating system directly to the radiators and hot water cylinder. It differs from a conventional boiler because many of its individual components are built into the boiler itself, increasing efficiency.




A three-point fitting shaped like a T that is used to connect three pipes together within a plumbing system.




The section of the drain that holds water (ex: the U-bend on a toilet), creating a seal that prevents waste fumes from travelling back into the house.


Unvented Hot Water Cylinder


An unvented hot water cylinder does not need a cold water tank and is connected directly to the mains. Completely sealed, water is heated within the cylinder, which includes inbuilt safety features such as an expansion unit to account for excess water.




A mechanical device that controls the flow of water through a pipe, available to suit different system pressures and pipe sizes.




A pipe that allows air into a drain system. This balances air pressure and prevents water in the traps from being siphoned off.


Vented Hot Water Cylinder


Here, a store of water from the mains is kept in a tank in the loft. Gravity carries this water down to the hot water cylinder via a vent pipe where it is then heated and stored for use in taps, radiators, showers and more.


Vent Pipe


A pipe that allows the release of air or water from a hot water system.


Water Main


The main underground pipe supplying water to an area.


Water Service Pipe


The primary pipe into a property from the water main. 

Posted by ChelseO
Tuesday, 7th February 2017, 06:04pm.
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