Which kind of stormwater drainage system is better to install?

The gravity flow drainage system is that the rainwater is collected by the roof gutter and discharged by gravity artesian flow through the riser connected under the rainwater bucket. This system line cannot be completely filled with water. When water flows down the wall of the riser, it generally only occupies a part of the riser section, and even a small part is water and part is air.

Gravity flow drainage is the traditional way of roof drainage. It has the characteristics of simple design and construction, safe and reliable operation, but its disadvantage is that there are relatively many pipelines and occupies more space positions.

Gravity flow stormwater systems require the flow of the control system to be within the designed gravity flow range. Otherwise, the excess flow of rainwater into the system, the flow regime will exceed gravity without pressure flow, and the violent pressure fluctuation will cause damage to the system, such as damage to the riser, water in the indoor inspection well and other safety accidents.

At the beginning of rainfall, the principle of gravity is used for drainage. When the rainfall increases and the water level on the roof reaches a certain height, the rainwater bucket will automatically insulate the air, resulting in siphoning, and the system will also be transformed into an efficient drainage system, pumping rainwater and draining downward. For large roofs, the whole roof drainage system can be composed of several subsystems, each subsystem has a gutter, so that the gutter can avoid expansion joints.

The design of the system is that when the rainwater depth in the gutter reaches a certain depth, the tail pipe is first filled with water to reach the siphon condition, and then the whole system produces a siphon, which can make the rainwater on the roof quickly discharged. Due to the large flow rate of siphon drainage, it should be discharged into the municipal rainwater drainage system through the energy dissipation well. When the rainfall is low, the siphon system is only used as a gravity flow system.

In this way, the siphon drainage system can drain rainwater that occurs once in decades with a much smaller line than the heavy flow drainage system.

Therefore, the difference is shown in the following diagram:

It is evident from the diagram that the water depth required in front of the bucket for the siphon drainage system is less than that of the gravity flow system for the same amount of water discharge. For example, the calculation shows that when the drainage volume is 40L s, the gravity flow rainwater pipe with a diameter of 300mm has a water depth of 100mm in front of the bucket, and the siphon rainwater pipe with a diameter of 100mm has a water depth of only 85mm in front of the bucket, which is very beneficial to the architectural and structural design of the roof. The pipe diameter used in the siphon system is not only smaller than the specific gravity flow, but can also be "less" than the gravity flow.

The system shown in the figure, i.e., one horizontal pipe and one riser, can be connected to more than ten rainwater buckets, while the gravity flow system requires multiple risers.

In addition, the transverse pipe of the siphon system can be installed horizontally, while the transverse pipe of the gravity flow system must have a slope of not less than that, which will make the end of the transverse pipe lower, thereby affecting the use of space or affecting the treatment of the building structure. Due to the small number of risers of the siphon system, they can be laid in stairwells, columns, etc., without taking up more space, and the horizontal pipes can also be laid in non-sensitive public corridors. In short, to give a favorable condition for the design of the building.

It depends on the application occasion

What is the specific content of the rainwater drainage system project, the following Zhongda Consulting will answer for you.

All parts of the rainwater drainage system are located outdoors, and there are no stormwater pipes inside the building, so there will be no leakage of pipes from indoor water supply equipment and water from the ground. According to whether there is a gutter on the roof, the external drainage system can be divided into two ways: drainage outside the ditch and drainage outside the gutter.

1.Drainage system outside the eaves.

The gutter drainage system is also known as the water downpipe drainage system, which is composed of the gutter, the rainwater bucket and the water downpipe (riser).

Rainwater that falls on the roof flows along the roof into the ditch. Then flow people after the rainwater bucket and the water fall into the pipe. Drain people outdoors on a loose slope or in an underground pipe trench.

This drainage system is suitable for the removal of rainwater from the roof of general residential buildings, public buildings with small roof areas and small single-span factories.

The gutters are often made of galvanized iron sheet or concrete. The water drop pipe is mostly made of No. 26 galvanized iron sheet, the interface is soldered, and the cross-sectional form is round or square. The water drop pipe can also be UPVC pipe, cast iron pipe or asbestos cement pipe.

The spacing of the water drop pipe is determined according to the intensity of the local rainstorm, the catchment area of the roof and the water flow capacity of the water drop. According to experience, generally 15-20m set up a DN100 mm water downpipe, its catchment area does not exceed 250 The water downpipe on the balcony can be used DN50 mm, 2Drainage system outside the gutter.

The gutter external drainage system consists of a gutter, a rainwater bucket, a drainage riser, and a discharge pipe. The pressure vessel system is collected by the gutter after the water is collected. The inlet and riser flow from the outfall to the outdoor stormwater drain.

This drainage system is suitable for multi-span industrial plants up to 100 m in length, as well as for buildings where stormwater pipes are not allowed.

For the drainage outside the gutter, the expansion joint or settlement joint of the building should be used as the water line of the roof hall. The length of the flow of the gutter should be arranged in combination with the expansion joint of the gutter, and should not be greater than 50 mIts slope should not be less than to prevent water accumulation at the end of the gutter.

A nozzle should be set at the end of the daughter, on the mountain or at the end of the gutter stocking nucleus, and the nozzle should be 50-100 mm lower than that of the gutter elm

Depending on the roof, the cross-sectional form of the gutter can be rectangular, trapezoidal, triangular or semicircular. The practice of gutters is generally to lay foam concrete or slag on the roof of the debate board, make a waterproof layer on it, and then remove a layer of mung bean sand. The gutter is plastered with cement mortar.

Prefabricated reinforced concrete troughs can also be used. The surface is plastered with 1,2 cement mortar.

Cast iron pipes and discharge pipes can be used for drainage risers, UPVC pipes, and asbestos cement pipes can also be used for low-rise workshops. When the riser drains directly to the ground, anti-erosion measures should be taken. In collapsible soil areas, direct drainage is not allowed, and risers in frozen areas need to take anti-freezing measures.

Gutter layout and riser laying requirements see Figure 4-13; The gutter rainwater bucket is connected with the riser.