As we celebrate 25 years in business, we are pleased to announce that Maryland Plumbing & Heating will become part of O’Connor Plumbing! The same services will continue to be provided and there are no changes to you! Please call 301-540-5050 to reach O’Connor’s service line. You can learn more about O’Connor Plumbing at


Plumbing Service Glossary


Access panel – a small opening in the wall or ceiling that provides access to key parts of the plumbing system

Adaptor – a fitting that links different types of pipes together

Aerator – a small device that screws into the end of your faucet spout and adds air to the flow of water, controlling the flow and reducing splashing.


Backflow – the flow of liquids or other substances, including dirty water, back into potable water distribution pipes.

Backflow preventer – a device made to prevent backflow, usually required for sprinkler systems, handheld showers, pullout faucet spouts or kitchen sprayers, etc.

Back pressure – pressure that resists the flow of a liquid in a piping system.

Back siphonage – negative pressure that causes backflow. This is one of the primary things backflow preventers are designed to work against.

Backup – a plumbing system that is backing up is overflowing due to a drain stoppage.

Backwater valve – a sewer line valve that prevents sewage from flowing back into the house.

Ballcock – this is the fill valve that controls the flow of water from the supply line into the toilet tank. It’s controlled by a float mechanism that floats in the tank. When the toilet is flushed, the float drops, opening the ballcock and releasing water into the tank or bowl.

Basket strainer – a basket strainer is, as the name suggests, a basket-shaped strainer with holes and a slot that fits into a sink or shower drain and filters water that runs through the drains so they don’t end up in the sewage system.

Bleed – to bleed a pipe is to drain it of excess air by opening a valve at the end or by using force or suction.

Boiler – a boiler is a sealed tank where water is heated. Boilers provide heat for radiators or hot water heaters.

Branch – any part of a drain system that doesn’t include the water main, risers or stacks.

Branch vents – a vent that connects one or more individual vents to a vent stack.

BTU – British thermal unit. This is the amount of energy required to raise the temperature of 1 lb of water by 1 F.


Catch basin – a large underground container for collecting storm water runoff as well as dirt and other debris to prevent them from polluting streams.

Check valve – type of backflow preventer that only allows water to flow in one direction.


Diaphragm – flexible membrane in a valve that deflects onto a rigid area of the valve body to regulate water flow from supply lines, eliminating the risk of debris buildup in the valve.

Dip tube – tube inside your water heater that sends cold water down to the bottom of the tank.

Discharge tube – pipe that connects your sump pump to the drain line.


Efficiency – a products ability to use input energy. Usually expressed as a percentage.

Effluent – liquid waste.

Elbow – pipe fitting with two openings that changes the direction of the line. Also called an ell. Elbows can come in a variety of angles.

Escutcheon – decorative metal shield beneath a faucet handle that covers the faucet stem and hole in the fixture or wall.

Expansion tank – tank designed to absorb excess pressure due to thermal expansion.


Fall (flow) – proper pitch of a pipe for adequate drainage.

Female fitting – receiving end of a pipe or fitting.

Fixture (plumbing) – devices that provide a supply of water and / or water disposal (sinks, tubs, toilets, etc.).

Flapper valve – valve on the bottom of the toilet tank that opens, allowing water to flow from the tank to the bowl.

Float ball – floating ball connected to ballcock inside the toilet tank that rises or falls depending on the water level, activating or deactivating the ballcock as needed.


Gas cock – plug valve installed in the main gas line and appliances.

Gas control – device that regulates gas pressure on water heater.

Gate – device that controls flow in a pipe, tunnel or conduit.

Gravity operated toilet – toilet that relies on the natural downward pressure of water to flush.

Gray water – waste water from sinks, showers and bathtubs (not toilets).


Horizontal branch – lateral pipe drains that run from plumbing fixtures to the waste stack, either in a building or in the soil.

Horizontal run – horizontal distance between the point where fluid enters a pipe and the point at which it leaves.

Hose bibb – outdoor faucet, also used to supply washing machines.

Hydronic – system of forced hot water used for heat (radiators, baseboard, convectors).


I.D. – abbreviation for “inside diameter”, the sizing standard for all pipes.

Indirect wastes – waste pipe used to convey gray water by discharging it into a plumbing fixture (such as a floor drain).

Instant water heater – water heater that heats water as it flows through a heating coil.


Jet – toilet feature designed to direct water flow into the trap quickly to start the siphon action.


Knockout plug – PVC test plug.


Leach field – porous soil area through which septic tank leach lines run and empty treated waste.

Leader – pipe that carries rainwater to the ground or sewer.


Main – primary supply artery for the drainage system or water supply into which all the branches connect.

Male threads – threads on the outside of pipes and fittings.

Manifold – fitting that serves as a distribution point, connecting a number of branches to the main.

Mechanicals – wiring, plumbing and HVAC system, along with all associated equipment, in a building.


Nipple – short length of pipe installed between couplings or fittings.


O.D. – abbreviation for “outside diameter”.

O-ring – round, rubber washer used to create a watertight seal. Usually used around valve stems.

Oakum – loosely woven hemp rope treated with a waterproofing agent and used to caulk joints in a bell and spigot pipe and fittings.

Outlet sewer – pipe section in a septic system that runs between the septic tank and drainage field.


Packing – fibrous material used on faucets to prevent leaks.

Packing nut – nut that holds the stem of a faucet in position and holds the packing material.

Polybutylene – flexible plastic tubing not used anymore due to pipes breaking.

Peak hour demand – time of day with the highest demand for hot water.

pH (potential hydrogen) – hydrogen concentration of water to denote acidity or alkalinity, measured on a scale of o to 14 (below 7 = acidity, above 7 = alkalinity).

Pitch – downward slope of drain pipe in the direction of water flow.

Plumb – this word has a few different meanings:

  • Precisely vertical
  • To test for or to make vertical
  • To perform plumbing work

Plumber’s putty – pliable putty used to seal joints between drain pieces and fixture surfaces.

Plunger – instrument usually with a rubber head used to create suction in a drain line or toilet to push a clog through the line.


Rated storage volume – quantity of water stored in a tank.

Reamer – grinding tool used to level or remove burrs from pipe or valve seats in faucets.

Revent – pipe installed to vent a fixture trap.

Rough-in – installation of the drain, waste, vent and supply lines in a structure to the proposed location of each fixture.


Saddle valve – valve mounted on a pipe run by a clamp used to make a quick connection to an existing line to provide water to a low-demand device that is no longer used.

Sanitary fitting – fitting that connects assorted pipes in a drain, waste and vent system designed to allow solid material to pass through without clogging.

Sanitary sewer – house drain that carries wastewater away from the house to a sewer system or septic tank.

Service – pipe connecting the water company’s piping to the water meter.

Stop valve – shutoff valve under sinks and toilets that allows the water supply to be cut off to one fixture without affective water supply to other fixtures.


T & P valve – temperature and pressure relief valve used to expel excess pressure or heat from inside a tank.

Tailpiece – section of pipe that runs between a fixture outlet and the trap.

Tank – fixture reservoir for flush water. In a conventional toilet, the ballcock, flush valve and trip lever are all installed in the tank.

Trap – curved section of a drain line that prevents sewer odors from escaping into the atmosphere. All fixtures that have drains have P-traps (except toilets that have them built into the porcelain).