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Standard rainwater drainage pipes on the roof

Rainwater drainage pipes are extremely important items when building any project. Reasonable drainage pipe design not only brings efficiency but also helps to increase durability and aesthetics, as well as saves construction costs. Therefore, choosing the type of pipe, the diameter of the drainage pipe, as well as the related factors in the design and construction process, is necessary to bring about the desired project both in terms of aesthetics and technique.



In fact, it has been proven that calculating a reasonable rainwater drainage system will ensure a high aesthetic value for the project. If the rainwater drainage system is not guaranteed, the amount of water will be affected depending on the level of structure, aesthetics, and durability, as well as increasing the investment cost of the project.


1. What is the purpose of the design of the household rainwater drainage pipe? Why is the calculation of the size of the rainwater pipe so important in construction?

The name of the storm drain pipe proves the role of this item in the construction process.

A rainwater drainage pipe system is a system of pipes, roofs, manholes, etc., to ensure the collection of all generated rainwater and ensure the technical flow of water.

The necessary requirement of the rainwater drainage system is to transport enough volume and volume of water drained by rain during the time of sudden increase in rainfall.


2. Principles of designing rainwater drainage system on the roof

- Rainwater drainage pipes are arranged to be the shortest.

- The slope ensures the fastest rainwater drainage.

- The diameter of the rainwater drainage pipe must ensure to maintain the drainage condition during the heaviest rain.


3. Why install a rainwater drainage system on the roof?

This answer is neither easy nor difficult. Answering this question requires understanding as well as understanding the principles of rainwater drainage. The roof drainage system is a part of the roof system, including purlins, corrugated iron, and drainage system... Due to such an important role, customers need to pay attention to the installation of roof drainage system slopes as well as flat roofs.



4. Experience in designing rainwater drainage systems for civil houses

For ordinary houses with a floor area of 100m2, 4 pipes of Ø60 will be arranged, and for large projects, pipes of Ø90 will be arranged with the quantity depending on the actual situation.


  • Calculation and design of rainwater drainage system for flat roofs

For flat-roof houses, it is necessary to have good rainwater drainage to limit water infiltration into the concrete to ensure structural durability as well as the aesthetic permeability of the building. The most important thing in the design of the rainwater drainage system is to calculate and determine the optimal slope for the best and most thorough drainage.


  • The optimal slope for drainage of flat roofs:

To ensure the best drainage, the required slope is from 2% to 5%. For a normal flat roof house, the drainage slope is determined in two ways as follows:

- For inclined load-bearing structures, i.e., flat roofs but pre-existing slopes or flat load-bearing structures, large reinforcement is required to adjust the slope to ensure the required slope. If the slope is not guaranteed, it is necessary to cast and install the panels so that the required slope is from 2% to 5%.

- For horizontal bearing structures, the upper slope adjustment layer is added to create the required slope from 2 to 5%.


  • How to arrange rainwater drainage system for flat roof house:

The most important part of this component is the roof septum, which is designed under the rim of the roof so that rainwater flows directly down the septum and from the seno into the hopper. In this case, a slope of 1-2% is required. Then it flows to the ground or drains into the common sewer.


In the design of civil and industrial works, rainwater drainage pipes can be arranged inside or outside so that it is most convenient and saves space. For low buildings, as well as small rainfall, it can flow freely without troughs, and for high buildings, there must be gutters leading directly to the ground or public sewers.


For some current civil works, in order to increase the aesthetics, people use the method of internal rainwater drainage; that is, rainwater goes into the wall and floor and then down to the common sewer. This system, although highly aesthetic, is prone to problems as well as difficult to solve when problems occur.




  • Structure of flat roof rainwater drainage components: Seno and Hopper

A seno is a component of an indoor rainwater drainage system, or in other words, a séno is a roof rain gutter or gutter.

The size of the sump depends a lot on the aperture as well as the amount of rainwater drainage on the roof.


Senotype classification:

Seno is very widely used in practice. Especially the assembled sedans. In the assembly, we divide into 2 types which are:

- The seno is monolithic, with the panel in one large structure.

- The seno is cast as an independent element.


Note: Seno is a temporary storage place for rainwater, so it is easy to seep and leak, so it is necessary to carefully waterproof it during construction.


If the rainwater drainage requirement of the seno is good, the required slope is usually from 2%


In the case of flat-roofed senos, the senos are constructed from panel-type concrete slabs or reinforced concrete. Note that when designing, the seno needs to have a minimum depth of 20 cm, and a minimum width of 20 cm. Constructed with mortar grade 75, waterproofed with professional anti-scratch or pure cement.

For the arrangement of stormwater drainage in the seno, usually, a 10m arrangement will install a 60mm pipe in order to collect the entire amount of rainwater drained.


Contact Local Rooter Corp.


If you would like a free quote on inspecting your plumbing system in San Jose and surrounding areas, our professional plumbers at Local Rooter are here to assist you. Call us at 408-641-9245 or contact us here

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