Typical toilet vent pipe design

Written by greg jackson | 13/05/2017
Typical toilet vent pipe design
The typical toilet vent pipe design has several basic features. (Toilet bowl and bidet in a toilet image by terex from Fotolia.com)

The plumbing system in any structure that contains a toilet must have a way to remove sewer gases. This involves a venting system that not only removes these harmful gases, but also ensures that the plumbing system continues to operate satisfactorily for many years. The typical toilet vent pipe system is based on these principles.

Basic structure of a drainage system

Any plumbing system that has fixtures that require drainage have basic elements that are necessary for the system to work properly. These include the drain pipe, a trap, and a drain or waste line. Drain and waste lines are typically angled downward in order to use gravity to remove the water being drained. The drainage lines for a toilet are generally 10 cm (4 inches) in diameter to prevent blockage of waste.

Elements of a toilet vent system

The venting system of a plumbing design that includes a toilet has several features that must be in place for the system to work properly. One of these is known as a trap. A plumbing trap is a must in any system. Traps are used in any drainage pipe, such as a sink drain, a bathtub drain or a toilet. The trap must be designed so that it maintains a steady amount of water between the drain and the removal pipe attached to the trap. This water acts as a barrier to prevent sewer gases from backing up into the drain after water runs through the system.

Other elements

The way in which water is contained within a plumbing trap is by the use of a venting system. These vents must be installed in such a way that they have constant access to the exterior of a structure to not only release the air that is created when water is forced through the plumbing, but to replace that same amount of air into the pipes. This method traps water between the drain and the drainage pipes in the plumbing trap.

Structure of a venting system

The typical toilet vent pipe design includes a trap at the drain, plumbing lines that run the flushed water to the sewer lines, and the vents. The drainage lines will have a pipe that runs to the vent and out through the roof, in most cases. This system is known as a vent stack, and can be used in either single-family structures or in more complicated plumbing systems found in apartment buildings and office buildings. The venting system will have these same elements regardless of the type and size of the structure if it has toilets within the plumbing set-up.

Important factors of any venting system

The main purpose of a toilet vent system, or any drainage system, is to draw out the air that is created when water flows through the system. This requires that no horizontal lines can be part of the venting system design. There are many situations in which plumbing lines cannot be run directly upward to a roof line. In these cases, vent lines must be angled to go around obstacles within the wall, such as electrical conduits or HVAC ducts. The maximum angle that can be used in these situations is a 45 degree angle to avoid horizontal lines.

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