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Homeowner’s Plumbing Dictionary

Plumbing plans and tools

Are you mystified by ABS, PVC and PEX? Don’t know a flange from a flapper? You’re not alone. Plumbing terms can be extremely confusing!

However, understanding plumbing terminology is not just for professionals—it’s crucial for every homeowner. Having a basic grasp of plumbing terms can help you understand how your system works, diagnose potential problems and communicate effectively with professionals about what is wrong with your system. It can also save you time, money and unnecessary stress.

When plumbers use certain terms or phrases, knowing what they mean can help you comprehend the issue at hand, the work that needs to be done and why it’s important. In essence, a little plumbing knowledge goes a long way toward maintaining a healthy and efficient home.

Here are 39 plumbing terms from Aspinwall Plumbing & Heating’s Homeowner’s Plumbing Dictionary, so you will know what they mean and how they impact the water inside your home:

ABS pipe: Acrylonitrile Butadiene Styrene, or ABS pipe, is a type of plastic piping that is often used in residential and commercial plumbing systems. It’s popular due to its strength, durability and ease of installation. However, ABS pipe is only used for wastewater, not drinkable water.

Backflow preventer: A backflow preventer is a device used to keep the clean, drinkable water in your pipes flowing in one direction, preventing it from flowing backward and potentially becoming contaminated.

Backup: A sewer backup, or sewage backup, is when sewage or dirty water bubbles up a drain into your home. Sometimes this happens in a contained area, such as a bathtub, but a backup also can cause dirty or contaminated water to come up any drains you might have on the floor of your basement. It happens when something prevents the water from flowing away from your home. Some homes also may experience backups during flooding or heavy rain.

Black water: Black water is a plumbing term to describe water that comes from your toilet. Although the water is not actually black, it contains fecal waste and urine, so it could be extremely harmful to drink.

BTU or British Thermal Unit: A British Thermal Unit (BTU) is a unit of measurement for energy. Each BTU is equal to the energy needed to raise the temperature of one pound of water by 1 degree Fahrenheit.

Closet bend: A closet bend is an angled pipe underneath your toilet. The purpose is to allow waste to exit your toilet and go into your pipe system without causing blockages.

Closet flange: A closet flange is a ring that fits over the pipe underneath your toilet. Its purpose is to attach the toilet to the drain pipe underneath it so waste can be flushed away.

Flange: A flange is a connection between two pipes—often a rib, collar or rim. It is used to strengthen a joint in the plumbing or attach two sections together. For example, there is a toilet flange underneath a toilet to connect the toilet to the pipes below.

Flex coupling: A flex coupling is a way to join two different kinds of pipe, or two pipes that may not be perfectly aligned. It often is made of rubber or plastic.

Gray water: Although it isn’t actually gray in color, gray water is a term used to describe water that drains from sinks, bathtubs, dishwashers, laundry machines and other appliances. It is not safe to drink, but is not as dangerous as black water, which is a plumbing term for water that comes from the toilet.

Heat exchanger: A heat exchanger transfers heat between a gas or a liquid. Common places in your home that use heat exchangers are the air conditioner, furnace, water heater and refrigerator.

Hose bib: A hose bib is another name for a faucet on the exterior of a home or building that you can connect to your garden hose.

Hydronic systems: In plumbing, a hydronic system uses a series of pipes containing hot or cold water that is used to heat or cool a home. Radiators and boilers are components of a hydronic system.

Main line, mainline, water main line and main water supply line: Depending on how these terms are used, someone can be referring to one of two very different things. It’s important to know the context in which these terms are used so that you can determine which one someone is talking about:

  • Water coming into your home: The main water supply line is a pipe that brings water from the water company to your property. Sometimes, this is also referred to as the main line, mainline or water main line.
  • Water leaving your home: Sometimes, people use similar terms when they are referring to the main drain line out of the house. That pipe, which carries used water away from your home to the city’s water main, is commonly referred to as a mainline, or main line as well.

Homeowner’s Plumbing Dictionary

Metal pipes: There are several types of metal pipes used for plumbing. The most common are galvanized steel, stainless steel, copper, brass and iron.

Mold: In plumbing, mold is a fungus that grows in wet, dark areas. It’s a common and potentially harmful result of water damage caused by a leak or burst pipe.

O-ring: An O-ring is a round piece of rubber, shaped like a ring, that is put inside joints in pipes or other plumbing connections to form a water-tight seal.

PEX pipe: PEX pipe, which is short for cross-linked polyethylene, is a flexible plastic pipe used in plumbing. Unlike PVC pipe, which is typically only used for cold water, PEX pipe can be used to transport both hot and cold water.

Pipe or piping system: Pipes are used to transport water into, throughout and away from your home. Common materials used for plumbing pipes are PVC, PEX, metal and ABS pipe.

Plumbing snake: A plumbing snake is a thin piece of material inserted down a drain to manually remove a clog. Often made of wire or a coil, it is also called a drain snake or drain auger.

Plumber’s tape: Also known as thread seal tape, plumber’s tape is a thin white tape that is used to prevent leaks in attachment and joints in pipes. It is wrapped around the threads of a pipe before the joint is fastened together, filling gaps between the threads and creating a more water-tight seal.

PVC pipe: Polyvinyl chloride piping, better known as PVC pipe, is a type of plastic piping commonly used in plumbing systems. It is durable, lightweight and easy to handle. However, PVC pipe is typically only used to transport cold water, because it can soften, lose shape and leak if exposed to very high temperatures.

Potable water: Potable water is safe for drinking or for food preparation. It is clean and uncontaminated.

Septic tank: A septic tank is part of a septic system, which is a water-treatment setup for properties that are not connected to municipal sewer systems. Wastewater goes from the house into an underground septic tank, where bacteria are used to decompose some of the waste. Treated water flows out of the septic tank into a leach field, where it drains into the ground. Septic systems are very common in rural areas.

Sump pump: A sump pump is used to remove excess water from basements. They work by pumping water out of the basement when the water level reaches a pre-set level. They are able to do this because the pump is built into a pit or basin, and they are programmed to turn on and pump water when the water line reaches a certain level in the pit.

Supply line: A supply line is a pipe that carries clean water from a public water main or private well into a building. They also are called water supply lines or service pipes.

Tap water: Tap water is drinkable, clean water that is distributed through a home by pipes and faucets, which are also called taps.

Toilet bowl: The toilet bowl is the part of the toilet where waste is deposited so it can be flushed away.

Toilet flapper: A toilet flapper is a component of a toilet that holds the water in the tank until it is flushed. It is controlled by the toilet lever, or handle. When you push the handle down, a chain pulls the toilet flapper up so the water can flush the waste away. Releasing the toilet handle allows the toilet flapper to fall back into place, recreating the seal so the tank can refill and be ready for the next flush.

Thermocouple: A thermocouple is a safety device on a water heater that senses if a pilot light is burning. If the thermocouple does not detect any flame, the gas valve will close to prevent gas from escaping the water heater and endangering people in the building. A failed thermocouple is a common reason for a water heater not to work.

Toilet wax ring: A toilet wax ring is a circle of wax used to create a watertight seal between the bottom of a toilet and the pipes underneath. This stops water and any sewage gasses from leaking out of the connection.

U-trap or P-trap: In plumbing, U-traps and P-traps are curved pipes under a drain to prevent sewer gas from coming up the pipe and into your home. They do this by trapping water in the bends, which prevents a seal that gas can’t penetrate. Their names refer to their shapes: U-traps are shaped like the letter U; P-traps look like the letter P laying on its side.

Valve: A valve is a device used to control the flow of water in a plumbing system by opening or closing.  They can regulate, start or stop the flow of water. They are typically installed a strategic place where it’s important to control the flow of water. They can be manual or automatic.

Vent: Plumbing vents are used to allow fresh air to get into a system and potentially harmful sewer gasses to safely exit, preventing them from getting into a home.

Water heater: A water heater is used to heat water for use in your household. Tank water heaters heat a drum of water, which is always ready for use. Tankless water heaters are smaller and heat the water as you need it, so there is no need for a storage tank.

Water meter: A water meter measures the amount of water a property uses. It is installed by the water supply company to track usage.

Zoning: In the context of plumbing, zoning describes the practice of dividing a building’s water systems into different areas, or zones. Each zone is controlled independently and has its own thermostat or control valve, so water temperature and flow intensity can be customized to that area.

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