The knowledge of trap

- Apr 03, 2018 -

The trap refers to a type of water-tight fitting provided inside a sanitary appliance or on the appliance drain section. The water trap is divided into the S-type trap, the P-type trap, the U-shaped trap, and S and P, u can illustrate the shape of the trap.


The trap is to set a certain height of water column on the drainage pipe of the sanitary appliance or the interior of the sanitary appliance to prevent the gas in the drainage pipe system from entering the interior accessories. The water column with a certain height in the trap is called a water seal.

The trap is one of the main attachments of the drainage pipe inside the building. Some sanitary equipment has traps (such as seated toilets) in the structure, and the structure does not have the industrial waste water receiver and domestic sewage pipe or other. When a drainage pipe that may generate harmful gas is connected, traps must be installed below the outlet.

Main species

The use of a wide range of traps, more types, generally have the following types:

(1) S-shaped trap. The place for vertical connection with a drainage cross pipe.

S-shape trap.jpg

(2) P-shaped trap. The place for horizontal and vertical connection with the drainage cross pipe or drainage stand pipe.

P-shape trap.jpg

(3) Bottle-type traps and traps with venting devices are generally located on the drainage pipes of sanitary appliances such as washbasins or sinks.

Bottle-shape trap.png

(4) Water storage box Same as the S-shaped trap, the installation is more flexible and easy to clean.

The main purpose

A certain height of water column (usually 50-100 mm) is formed in it. The height of this part of the water is called the height of the water seal. It can prevent all kinds of polluted gases and bugs from entering the room. In order to ensure the normal function of the water seal, the design of the drainage pipe must consider the appropriate ventilation pipe.


The water trap seal is not easily damaged due to insufficient water seal depth, and some sanitary appliances are used for a long period of time, especially for floor drains. There is no supplemental water for a long period of time. The water seal surface continuously evaporates and loses its water seal effect. This is the main reason for the odor escape. Therefore, it is required that the management personnel should have common sense in this area. It is necessary to regularly fill the trap portion of the floor drain and maintain a certain height of the water seal.

In recent years, dual-channel and three-channel floor drains produced by some manufacturers in China have solved the problem of replenishment of water and odors, and some countries have adopted the practice of setting up water injection pipes for the starting point drains.

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