The Operations of the DWV System

A metal rusted drain gutter draining water

A DWV plumbing system is called so because it contains three types of pipes: Drain, Waste, and Vent. These pipes are responsible for carrying water waste and sewage away from your home. Have you ever wondered how your plumbing system works and where does all the water go and how? If you have, you just got lucky. Here is how a DWV System works.

Types and Functions of Pipes

As mentioned, the system consists of 3 different types of pipes, Drain, Waste, and Vent. The DWV system can be divided into two parts Drain-Waste and Vent.

Drain and Waste Pipes

The Drain and Waste pipes carry the sewage away from your house to the public sewer and septic tank. These pipes slope downward so that the wastewater and sewage can be easily carried by gravity and don’t stay in the lines.

Vent Pipes

The Vent pipes do two things:

  • It gets rid of the sewage gases through the exhaust pipes on the roof.
  • It airs the drain and waste pipes to make sure that the sewage keeps moving.

How Does It Work?

There are various components in the DWV system that operate collectively to make the system work.


Every house has one main stack. It’s a vertical pipe about 3–4 inches in diameter running from the roof to the main sewer line.

Drain – Waste Pipes

Both the drain and waste pipes are horizontal and downward sloping to ensure that wastewater and sewage don’t stay in the pipes. These pipes run into the stack, which then carries the waste, with the help of gravity, to the main sewer.

Vent Pipes

The air from the vent pipes ensures that the sewage is moving smoothly along the drain pipes.

Plumbing Traps

Each fixture, like the sink and the toilet, has a curved plumbing trap. The water in these traps prevents sewage gases to escape, and is replaced every time these fixtures are used. The plumbing trap in the toilet is called an S trap, whereas the one in the sink is called a P trap due to the shape of the curve.

Plumbing trap

Sanitary Tee

A sanitary tee regulates which waste goes where. Sewage and water waste go to the stack while the gases go out through the vent to the exhaust pipes of the roof.

Sizes of Pipes

DWV pipes are about 1 ¼ –4 inches in diameter. The toilet soil tank pipe is about 4 inches, the shower is 2 inches, whereas sink, bathtubs, and all the other fixtures are 1 ¼ – 2 inches. Most of the drain pipes are cast iron, copper, or ABS plastic.

DVS plumbing systems can be really complicated to understand and way more expensive to repair if the damage is significant. Therefore, it’s crucial to get your plumbing inspected before investing in your house, real estate, or commercial property. A poor plumbing and wiring system can also make it difficult for you to get homeowner’s insurance. It’s, therefore, necessary that you get the property fully inspected before making any decision.

If you’re looking for home inspection services in Houston, contact HTX Home Inspection. We are Certified home inspector that provides real estate inspection, property inspections, and residential inspection services Houston. For more details, please visit our website or contact us on (281) 816-7007.


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