Types of Pipes in Drainage System of Residential Building

We use various types and different sizes of drainage pipes in the different locations for various purpose in residential building’s drainage system. Sometimes size/diameter of pipe is not shown in the drawing. In that situation we use typical size of pipe for a particular purpose. Because size of pipe doesn’t vary much in residential building. Types and size of drainage pipes is also a much asked question in job interviews. I also faced this question once. That is why I’m writing about this in this post.

This post will answer the following questions -

  • what are the different types of pipes used in the drainage system of residential building.
  • what sizes of drainage pipes are used in residential building’s drainage system?

drainage system in residential building
Now lets find the answer of above questions.

We use following types of drainage pipes in residential building -

  • Waste pipe/Waste stack,
  • Soil pipe/Soil stack,
  • Rain Water Pipe, and
  • Vent pipe.

The descriptions of each type of drainage pipe below will give you a complete view of drainage system of a residential building -

Waste pipe: This is a 4 inches dia pipe go vertically along building height. Waste water from bath-tub, basin, shower, kitchen etc. go through this pipe. Waste pipe is also called waste stake.

Different size of waste water pipe at different place -
Floor trap to waste stack – 4 inches.
Basin to floor trap – 1.25 inch.
Shower/bath tub to floor trap – 1.5 inches.
Kitchen sink to floor trap – 2 inches.

Soil pipe/Soil stack: Dirt from water-closet is discharged through this type of pipe. Size of soil pipe is 4 inches. It is placed parallel with waste stack.
Size of connecting pipe between W/C and soil stack is 4 inches.

Rain water pipe: In short, it’s expressed by RWP. It is also a vertical pipe go along building height. Rain water from roof and other open places go through it.
For removing rain water from veranda we use 2 inches dia pipe and connect it with RWP.

Vent pipe: Vent pipe is used to remove bad air from soil stack and waste stack. Typically 2 inches dia pipe is used for this purpose. Vent pipe is the short form of ventilation pipe.
Other than these pipes, there are also some other pipes of 6 inches dia we use below ground level. Those are main drainage line. These main drainage line collect dirty liquids from soil stack and waste stack separately and discharge to desired destination. Such as, collected liquid from soil stack discharges to septic tank and from waste stack to municipality drain.

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