What Are Drains?

What do you mean by drains?

When you drain something, you remove the liquid from it, typically by pouring it away or allowing it to flow away, whereas when something drains, liquid flows away or out of it. Drainage is the process by which water leaves a body or an area of land. In this post, we discuss what drains are and how they work.

There are many types of drains, such as domestic, commercial, and industrial drains. A domestic drain is usually found in a home or other buildings that have a private system for disposing of water. Commercial drains are used in warehouses, factories, and office buildings. Industrial drains are used in mines, quarries, and power stations. The pipes that are used in drains are made of plastic, steel, or copper. For a short and digestible guide on pipe materials read our article.

Drainage Systems

Drainage systems are made up of pipes that transport sewage, rainwater, or other liquid waste to a site of disposal, which could be the sewer system or a septic tank. Its primary goal is to collect and eliminate wastewater while keeping sewer gases out of the structure. Unlike the piping that transports water into a structure, drainage piping is typically made of plastic or metal.

Drainage systems are usually made up of a network of pipes, drains, and sewers. They are designed to carry water away from homes, businesses, and other buildings. They can be made of concrete, clay, or other materials. They are usually buried underground. The pipes are made of materials such as iron, steel, copper, or plastic. They are connected to each other by drains. The drains are usually made of cast iron, brick, or concrete. They should also be regularly maintained.

If your drain systems are starting to break down and cause issues, it might be the time to get them relined.

What is the purpose of a drain?

Unwanted water or waste liquids can be burnt off in a drain by directing it to a more suitable area, into a container, or into sewers or stormwater mains as a waste discharge to be processed or released.

How are drains constructed?

They would be laid down in a trench in a normal drainage system, which would then be filled with coarse granular material such as gravel, sea shells, stone, or rock. The geotextile is then folded over the stone, and the trench is filled with dirt.

What are the parts of a drain called?

While we commonly refer to this system as drain pipes, it is actually referred to as the DWV system which stands for Drain-Waste-Vent system. The name DWV signifies that this pipe network not only drains wastewater and solid wastes to the municipal sewer or septic field, but it also serves as a vent system that enables fresh air into the drain system.

Fixture Drain

Everyone is familiar with the upper, visible area of a tub, shower, or sink drain. Each drain pathway begins with an opening in the fixture, which is commonly connected with a plug or stopper, through which wastewater flows from the fixture to the sewer lines or septic field.

While this is the most visible component, drain problems are rarely caused by it. Except when gaskets or washers cause a tub or sink bowl to leak, drain clogs are nearly typically caused downstream from the fixture drain holes. When hair jams a pop-up stopper in a bathroom sink or bathtub, this is the one exception.


The fixture drain opening leads to a curved segment of pipe known as the P trap, which is generally a 1 1/4 to 2-inch diameter segment of pipe with a sharp curved bend in it, shaped like the letter P, immediately beneath a sink, bathtub, or other plumbing fixture.

This drain trap’s purpose is to hold standing water, which shuts the drain system and prevents sewage gases from rising into your home from the sewer system. If you’ve ever returned home from a lengthy vacation and detected a slight sewage gas odor in the air, it’s most likely due to standing water in the drain traps evaporating and allowing the sewer odor into your home.

Toilet Traps

Although it is not immediately obvious, every toilet has its own curved drain trap, which you may be able to notice if you look at the toilet bowl unit from the side. This built-in trap performs the same function as a sink drain trap in that it traps water and prevents sewer gases from entering the residence.

Clothes Washer Stand Pipes

The drain trap that services your clothes washer is another particular type of drain trap. The washing machine drain tube empties into an uncovered standpipe, which leads to a curved drain trap, which goes to a branch drain, and then to the main drain. The majority of these components may be disguised under finished walls, but the standpipe itself is frequently visible. The standpipe system might be composed of galvanized iron, brass, PVC, or ABS plastic, depending on the age of your plumbing installation.

Branch Drains

Branch drain lines run horizontally with a little downward slope, known as pitch, connecting each fixture drain trap to soil stacks, which lead to main drain lines. Branch drains are frequently concealed by a completed wall, ceiling, and floor surfaces. They are typically 1 1/2 to 2-inch diameter pipes manufactured of a variety of materials.

Soil Stack

Branch drains discharge into soil stacks or main drain stacks, which are enormous diameter vertical pipes, as they reach the end of their horizontal runs. Wastewater and solid wastes will now be carried down into the main drain pipes that lead to the city sewage system or septic field. Soil stacks are larger pipes with a diameter of 3 to 4 inches.

Soil Stack Vents

The DWV system’s venting component is located in the upper half of the vertical soil stack. Following it higher, the vent stack enters your home’s roof, where it is open to the outside air. The vent ensures that the whole drain system has uniform air pressure. This is necessary to prevent water from being drawn out of the individual drain traps by the suction power of the water traveling through the pipes.

If you’ve ever heard a drain gurgle as you empty it, it’s the sound of a low-pressure vacuum straining to suck water out of the drain traps. If the vent system is functioning properly, this suction will never reach the point where water is pulled out.

Sewer Line Clean-Out

The main house trap or sewer clean-out is only for emergencies and routine cleaning. It is typically found in a cap or hub attached to a 3 to 4-inch diameter pipe rising from a concrete floor in a basement or utility room. It is sometimes flush mounted onto the floor. In some regions, the clean-out is installed in an in-ground fitting directly outside the home’s foundation.

Main Drain Line

All wastewater from your home is carried to the municipal sewage line by a single main drain pipe that normally runs horizontally, but with a small downward slope, under your home’s lowest floor down to the municipal sewer main or out to the septic field. If the street sewer or septic field is not low enough, the main drain pipe may be hanging along the wall in your lowest floor before exiting the structure.

This 4-inch diameter pipe could be made of ABS or PVC plastic, clay, or cast iron. The mainline is rarely visible because it normally runs beneath the basement or foundation slab of a house. This drain pipe will most likely be seen only after major repairs or additions to your home.

Municipal Sewer Main

The municipal sewer main is the end point of your home’s drainage system. Your home’s main drain pipe is perpendicular to the sewer main and is slanted downward to promote waste movement. Because the municipal connection is owned by a city, county, or wastewater district, you have no authority over it.

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