What Is a Plumbing Drainage System?

A plumbing drainage system is a way to get the waste water out of a house. This comprehensive post by the Plumbers in Thousand Oaks experts at Candu Plumbing & Rooter uses gravity rather than pressure to transfer water. It has pipes connecting all of your water appliances, such as sinks and toilets.

The wastewater from these appliances passes through a small pipe inside your home and then connects to a larger pipe under the road. From there, the water flows through municipal sewers and eventually reaches a sewage treatment facility.


Traps are commonly used in a plumbing drainage system to catch water and prevent backflows. The S-trap, for example, is made up of a U-shaped loop that prevents sewer gasses from entering the system. The drawback of the S-trap is that it cannot capture a large volume of water because water flowing downstream in the pipe pulls water out of the trap.


Stacks in a plumbing drainage system allow water to travel downward in two different ways. The first type drains water down a horizontal stack, and the second type is vertical. Both types have one thing in common: they drain waste water downward. Both types of stacks must maintain a certain velocity. Usually, drainage systems must have a minimum velocity of 2 feet per second. In addition, the pitch must be at least 1/4 inch per foot, although some codes require it to be more.

Branch lines

The plumbing drainage system includes a variety of branch lines. These are pipes that run from the main sewer or drain to each fixture. These branches can be vertical or horizontal. Horizontal branches are not recommended because they can interfere with flow or cause a back-up of water. In addition, they can cause extreme pressure fluctuations.


P-traps are important to your plumbing drainage system. They can prevent sewer gas and other dangerous fumes from entering your home. You should replace your P-traps once in a while. If you have a trap installed in your bathroom, check it frequently for proper function.

Soil stacks

Soil stacks in plumbing drainage systems connect interior plumbing to the sewer and vent waste gases outside of a building. These pipes may be found in homes, office buildings, or other commercial facilities. They are vertical pipes that run above the floor of a building and vent sewage and greywater to the roof. They are typically made of cast iron or uPVC.

Interceptor drains

Interceptor drains are a critical part of a plumbing drainage system. If they are not maintained properly, they can clog and create a stench. Regular drain pumping and cleaning can help prevent this problem and maintain the plumbing drainage system in good condition.

DWV systems

A DWV system is a specialized drain system used in a building’s plumbing drainage system. It helps to manage and clean unusual waste, such as grease and food waste, before the waste flows through the municipal sewer system.

These systems should be properly maintained to prevent the accumulation of chemicals and other waste. It is also important to follow manufacturer maintenance recommendations, including dilution of cleaning chemicals. Cleaning and maintenance of a DWV system can be done by jetting, drain cleaning, cabling, or rodding.

Candu Plumbing & Rooter
22144 Eccles St, Canoga Park, CA 91304
(855) 522-2638