Typical projects of individual residential construction or industrial sites imply the availability of design documentation for the calculation of storm sewers. The code of rules SP 32.13330.2012 contains all the formulas necessary for the calculation, tabular values and coefficients. Since the lay person who for the first time holds the plan in their hands cannot be figured out without help, here is the basic information on how to carry out the calculations and not to confuse yourself even more, reading the features of the hydraulic calculation of the storm drain.
Rules and recommendations for the arrangement of a storm drain
The main goal that is pursued in the process of studying the arrangement of sewers is the accurate calculation of the diameter and slope of the pipe, depending on the amount of precipitation falling in a particular area.
Important! The insufficient throughput of the water supply system leads to a significant decrease in the efficiency of the sewer line as a whole. And this threatens to flood the territory adjacent to the house during heavy rains.
The arrangement of storm sewers is strictly regulated and regulated by SNiP. Remember that the drainage system is an essential element, regardless of the purpose of the structure.
Sewer Expert Tips
It is not enough to comply with the hydraulic calculation of storm sewers, so that the system functions properly, listen to some recommendations:
- A separate drainage system is installed for household wastewater and industrial waste.
- The place of release of effluents into natural reservoirs is agreed with the Sanitary and Epidemiological Service, bodies of water bodies protection.
- It is legally allowed to direct surface water from private farms directly to the central sewer, without giving in to their preliminary treatment.
- For industrial enterprises, effluents must be passed through treatment plants.
- The performance of centralized treatment facilities and its throughput determine the possibility of discharge of atmospheric precipitation from territories adjacent to private and industrial facilities.
- Whenever possible, try to organize a gravity flow of surface water.
- If it is required to provide a large production site or an entire settlement with a water supply system, then this is usually a closed branch.
- Low-rise and suburban facilities are equipped with open sewer networks.
- Combinations of open and closed drainage systems in private individual residential construction have gained practical application.
What formulas to use for calculating stormwater
To determine the cross-section of the drainage pipes, calculate the flow rate of rainfall falling in the region of residence. This factor depends on climatic and weather conditions.
The calculations are carried out according to the formula: Qr = q 20 Y F , where
- q20 denotes the calculated intensity of precipitation over 20 minutes;
- Y is the moisture absorption coefficient of the coating (1.0 for roofing, 0.95 for soil, 0.85 for concrete, 0.4 for crushed stone).
How is water used in pressure mode
In the hydraulic calculation of storm sewers, an adjustment is made for the fill factor of a free drain in the event of a pressure condition (b):
Q = Qr b , where b is taken from the table:
Rain Duration Indicators (n) | B value |
0.75 | 0.655 |
0.65 | 0.705 |
0.55 | 0.755 |
0.45 | 0.805 |
Important! The value of n depends on the geographical location of the object.
Coefficient n | Area |
0.455 | The coast of the Barents and the White Sea |
0.595 | Northern region of the European part of Russia |
0.575 | The lower reaches of the Don and Volga rivers |
0.665 | Lower Volga |
0.475 | Middle strip of Siberia |
0.525 | Eastern part of Siberia |
0.585 | Western Siberia |
0.485 | Altai mountains |
0.315 | Coast of the Sea of Okhotsk |
Important! when the slope of the terrain is 1-3 cm per 1 m, the coefficient b increases to 15%. If the bias is greater, then it is considered to be 1 for the indicator.
Take an example with the calculation of storm sewers.
Practical calculation of water throughput
Very often, the reason for the non-functionality of storm sewers is the neglect by the designers of the details of the calculation. Based on the general instructions of SNiP, repairmen and installers often make mistakes.
When calculating the diameter of storm sewers, pipes with a cross section of 200-250 mm are often used. This is the best indicator for the smooth movement of sewage through pipes. Even if precipitation is more intense.
Important! Preliminary calculation and purchase of the necessary parts in accordance with the norms and requirements helps to reduce costs without affecting the functionality of the network.
System throughput calculation example
For the area of the house territory, we take 100 m 2 , which is 0.01 from 1 hectare of land. Presumably we will divert water from this territory. Assume that the object is located in the Moscow region.
Based on the calculation table, it is determined that q20 for Moscow and microdistricts is 80 l / s. The moisture absorption coefficient for the roof is 1.
Based on certain indicators, the calculation of rainwater is as follows: Qr = 80 x 0.01 = 0.8 l / s.
In 90% of cases, the roof slope exceeds 0.03 (> 3 cm per 1 m), then the fill factor of the free tank during the pressure mode is taken as 1. From this it emerges that: Q = Qr = 0.8 l / s.
Important! After determining the indicators for calculating rainwater , you will have the opportunity not only to calculate the diameter of the pipe for storm sewers, but also to determine the necessary slope of the flow.
Good recommendations are given in A. Ya. Dobromyslov’s handbook “Tables for hydraulic calculations of pipelines made of polymer materials. Pressureless pipelines. " Here, the novice master will find the calculated data presented in the form of tables. It is definitely clear that for a flow rate of 0.8 l / s, a pipe with this diameter and slope is suitable:
- 50 / 0.03;
- 63 / 0.02;
- 75 / 0.01.
Important! Remember that pipe slope is inversely proportional to diameter.
Practical Tips For Building A Storm Storm
It is easy to guess that the design begins with the selection and procurement of material. And here the main thing is not to make a mistake in the choice, because otherwise all the work will go down the drain.
What material is suitable for the pipeline
According to SNiP, the use of asbestos-cement, steel and plastic (PVC) pipes is permissible.
Although asbestos-cement pipes are used, they are very rare. This is an economical option, but the material is fragile and heavy (1 m pipe with a cross section of 100 mm weighs at least 25 kg).
Steel water supply will be easier, but there is a but! Metal is prone to corrosion.
Therefore, PVC plastic products are preferable. Combining light weight, the ability to operate for a long time, ease of installation.
Features of laying depth
When designing and calculating stormwater treatment plants, soil characteristics are also taken into account, including the level of soil freezing. The optimal location of the pipe is below the freezing line of the soil, but above groundwater. It is not easy to observe these conditions because of the uneven terrain, because it is determined that the pipe should be no less than 70 cm to the surface of the earth.
Principle of installation of risers
It is impossible to imagine storm sewers without risers with point / linear storm water inlets connected to them, the vertical fastening of which is carried out using clamps.
Important! Note that the calculation of the interval for fastening the risers of storm sewers takes place depending on the type of material used. If it is PVC, then the clamps are fastened every 2 meters, if the steel is 1.35 m.
Secured territory
The SNiP provides for the organization of "security zones" in close proximity to stormwater. Remember that from the building, garden, park, landfill, parking to the sewer should be at least 3 m.
Design is the most important stage of the entire system of arrangement and calculation of pipes for storm sewers, regardless of the type of structure.
Here are the basic formulas that are useful in the calculations for both the craftsman and the beginner. But this method may turn out to be false if there are specific installation conditions (water pH, soil acidity, the number of bends and turns along the entire length of the sewer). The surest decision is to entrust the work to specialists who, in the course of hydraulic calculation of storm sewers, count every trifle using an example. This option is efficient and economical.
Can you imagine a landscaped area without storm sewers? What would the yard turn into due to heavy rain or thunder? There would be a lake in front of the house, and the exterior finish would soon deteriorate due to the effects of water, leaving no other options but to overhaul the facade of the house and the surrounding area.
Many ask the question of why the city drains can not cope with the drainage, and the whole village turns into a real wormwood. Neglecting the recommendations for calculating drainage systems in individual residential construction, a person makes up for one of the factors contributing to the malfunctioning of the entire drainage central system. Further, at the places of the main nodes, unscrupulous masters, trying to save money, neglect the same, putting them at risk of an immediate malfunction in the entire city network. Therefore, traffic jams, blockages are formed, low system capacity, flooding.
Understanding that the calculation of sewage is an important factor, and you cannot do without replenishment, will save you from a number of common problems. The main thing is to do everything right, and the sewage system will work properly.