Drain, Waste, and Plumbing Vent Systems Explained

Drain waste and vent piping are the two most important components in plumbing. These are the systems that take water away from your home. Let us examine how do they work.

Drain Waste-Vent System and Gravity

Earlier galvanized caste iron was used in the piping system, but now-a-days PVC piping is generally used. PVC piping is much better than the galvanized caste iron, as the later one clogs much easier. This distribution PVC piping system brings the water to the toilet bowl and the drain waste-vent system takes all the used water and waste away from the home to the sewer or septic system.

The functions of most sewer systems are based on gravity. That is the reason why everything goes down. In this process, the wastewater runs down the drain, enters the waste line, and finally leaves the bowl. Supply lines in the drainage system are fitted at forty or ninety degree angles. This drainage specification goes with the flow and helps the gravity of the sewer system to move the wastewater.

The Venting System
Venting system is a piping system and one of the most important components of drainage. The venting system consists of pipes. You must have noticed several pipes sticking up through the roofs of the houses in your neighborhood. These pipes are the venting system.

This system is also an essential requirement by the building code, as it prevents the water to draw out of the traps that are under sinks. Moreover, the other main function of this system is to allow gases to escape. It also helps wastewater to drain properly by relieving air pressure.

House Trap and Lateral Line
When the plumber ties the waste water pipes into the sewer line, he/she also installs house trap and lateral line. The main function of the house trap is to keep the waste and odors flowing out of the home, while the lateral line ties the house to the municipal sewer line.

This lateral line first goes into a sewer system down the street, and then it collects through a main distribution line, and finally goes to a sewer processing plant.

Air Admittance Vents
Air admittance vents are fitted under the sink. It helps sewer gases from coming out while drawing a bit of air in from under the sink. This way, these vents save money for you by reducing the amount of waste line vent stacks that you run. Moreover, they also help in reducing the possible number of penetrations through the roof.

Other Important Things
- The sewage lines coming into the house must be higher than where they go to connect to the city sewer line. This is an essential requirement, as we know that the sewage moves by gravity.

- There must be at least 2%-3% fall in your sewer system. However, it depends on the elevation of your home as well as the elevation of the city, which is the location of the connection.

- The fall the drain waste-vent system that carries fluids through the sewage system must be at least 0.25 inch per foot.

- There must be two-degree fall into the main line for the lateral.

Hence, here we see what are the components of a drain waste-vent system, and how do they work.
 

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