What are single grate and double grate drains?

Single grate rainwater outlet refers to one grate rainwater collection outlet, and double grate rainwater outlet refers to two grate rainwater collection outlets.

Single grate rainwater outlet: flat grate type, with the same height and width as the road flat stone, which collects rainwater through the cross slope of the road. Side-row type (it should be partial ditch type), this drainage is through the side stone drainage.

Rainwater grate is made by welding flat steel and twisted square steel or flat steel and flat steel. Rain grate has the advantages of beautiful appearance, best drainage, high strength, many specifications and low cost, so it is usually used in steel grating. With the development of science and technology, a brand-new composite water grate is formed by using resin or plastic reinforcement and inorganic filler. Its advantages are lighter weight and lower cost than that of cast iron grate, but its strength is not as high as that of cast iron grate.

Extended data

The structure of the rain inlet includes three parts: intake grille, shaft and connecting pipe. The intake grille of the rain outlet can be made of cast iron, reinforced concrete and stone. Using reinforced concrete or stone air intake grille can save steel, but its water intake capacity is far less than that of cast iron air intake grille. In some cities, in order to strengthen the water intake capacity of reinforced concrete or stone intake grates, the bottom of the side ditch of the rain outlet is lowered by several centimeters, but it causes inconvenience to traffic and may even lead to traffic accidents.

The direction of the water intake grate is also closely related to the water intake capacity. Grid parallel to the direction of water flow is better than vertical one. Therefore, in some places, water intake grates are designed to be criss-crossed to discharge rainwater flowing from different directions on the road surface. Rainwater outlet shaft can be prefabricated by brick or reinforced concrete, and can also be made of top concrete pipe.

Pollutant interception facilities should be set up at the rain mouth to reduce the insoluble pollutants generated by surface runoff from entering the receiving water body. In order to avoid odor overflow from sewage, measures such as setting water seal or adding chemicals should be taken to prevent odor overflow from rainwater outlet of combined system. Therefore, the depth of the rain outlet should not be greater than 1m generally, and sludge sedimentation tanks should be set up as needed.

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