Storm sewage is one of the most important systems for equipping a residential area, which, unfortunately, many owners simply forget about or treat it too lightly. And it is completely in vain - the hopes that rain or melt water will go away by itself often lead to the gradual swamping of the territory, to the destruction or failure of the laid paths and platforms, to the erosion and erosion of the structures of the foundations of the erected buildings, waterlogging of their walls and other negative consequences.
Storm sewage includes many different elements that are responsible for a specific area of water collection, for several such areas, or for the entire system as a whole - these are storm water inlets, pipes, wells, collectors. In order for them to be able to cope with their task, their parameters must correspond to the expected volumes of water. And when planning a system, the calculator for calculating the volume of stormwater, offered to the reader's attention, may be useful.
Below, under the calculator, a brief explanation of how it works will be given.
Having started the construction of a country cottage or house, a well-thought-out preliminary design documentation and estimate will always be a reasonable step. To save and optimize all upcoming construction and installation processes of sewer storm systems, compliance with SNiP - building codes and regulations, as well as a well-compiled estimate will help.
Every year, from 50 to 100 tons of precipitation descends through the drainage system of an ordinary private house, in the form of rain and melt water. If we imagine that rain flows uncontrollably begin to flow onto the site, then the soil will be oversaturated with moisture. IN summer period puddles on the surface of the site will not dry out for a long time, which will attract hordes of mosquitoes, and the winter season will always be fraught with ice.
Everything would be fine, but an excess amount of moisture in the soil will eventually begin to destroy the foundation of a wooden house. Water, therefore, should be diverted not only from the house itself and the territory of the site. Its excess must be removed from sidewalk paths and coatings. Installing a storm sewer and drainage system will help protect your home from excessive dampness, thereby extending its life, as well as reducing possible repair costs.
Budgeting should take into account:
- the expected quantity and volume of waste water;
- the location of the plumbing system and equipment in the house;
- the layout of the pipeline in the house.
If the sewerage project so requires, then the estimate will need to indicate recommendations regarding the selection of drainage pumps.
It is reasonable to immediately order an estimate for both sewerage and water supply. Thus, you will not have to deal with possible inconsistencies in the project. And from experience it follows that they certainly begin if estimates for sewerage and water supply are ordered from different companies and at different times.
The difference between types of storm sewers
- Open type - the simplest, from the standpoint of design and installation. An open storm system is the least expensive from a financial point of view and involves the collection of surface sewers with their discharge through open gutters or special drainage channels. You can see more on the video.
- A closed storm drainage system is somewhat more complicated. It needs careful planning. The installation of closed-type storm sewers is most often carried out by professionals. In addition to channels and gutters that drain water, this sewer system contains rain receivers and a pipeline of the drainage system that runs underground.
- A mixed storm system is an option that combines a closed system with an open one. Such a system is most often installed in areas with a large area, or when it is necessary to reduce possible costs. More on video.
The depth of placement of pipes during the construction of stormwater pipes
Questions about the required depth of storm water are discussed at all construction forums, however, in SNiP - building codes and the rules, there is already a clear answer that the installation depth of storm sewers to a minimum is determined empirically by those operational systems that are already used in a particular area. It is these rules that prevent unforeseen repairs associated with improper installation of stormwater.
- The device, as well as the actual installation of a private house stormwater installation, needs to comply with certain subtleties. The optimal width of gutters in private construction is from 100 to 130 mm. It depends on their throughput and the conditions of the place where they will be installed.
- If the drainage system is arranged on a base that is limited in height, then the installation depth of the channel becomes very significant.
- When choosing drains for organizing such drainage, it must be borne in mind that drains that are not very deep here will be more convenient.
- With other options for drainage devices in areas, the depth will not affect the installation work on storm sewers.
- To install drainage channels, a layer of concrete for the trench is required.
- A sand trap must be installed at the bottom mark of the route.
- After that, you need to draw a line for laying channels with a cord. Specialists recommend the use of sealants - sealing compounds during the installation of the system.
- To connect the channels at an angle, they need to be sawn.
- Ready-made corner elements and designs of easy-to-assemble gutters right at the installation site are considered convenient for installation. When assembled, these parts form a cross or T-shaped structure. They are practical and rarely need to be repaired.
How to create slope
- From experience, several options arose for the slope device:
- stepped slope through the use of channels of different heights;
- creation of a device with a slope of the ground;
- the use of channels with a slope of the inner surface;
For plastic gutters, which have a very small thickness and weight, it will be convenient to immediately dig a trench with a slight slope. If, however, they are used for the slope device, then it would be more logical to use a product with an inner surface that already has a slope. In these cases, it is permissible to install a stepped scheme with gutter structures of different heights.
Stormwater prevention and repair
If it becomes noticeable that the flow of water in the system has become worse than before, then it is necessary to inspect and, if necessary, repair the storm sewer. It is necessary to identify the places where the problem happened. Usually, repair work consists of cleaning the entire system or partial replacement of elements that are out of order.
To clean the sewer pipes of storm sewers, which tend to clog from time to time, a metal cable should be used. It is introduced into the pipe, with scrolling, moving forward along the pipe - to the place of blockage. Having found the "density" where the passage of water is disturbed, this blockage should be broken by intensive rotation of the cable.
The option of chemical or thermal sewer cleaning is possible. But due to its complexity, it is better to do the work only for professionals.
A laborious process is the replacement of pipes that are laid underground. Some time ago, storm sewers consisted of steel pipes. Their service life is short. If it is necessary to repair the storm drain, the old steel elements from the system are immediately replaced with plastic ones.
Cost and prices
In any installation device, the cost of work that requires the installation of a storm drain fluctuates. The price depends on the amount of work to be done. The cost may vary depending on the length of the storm sewer. But this is not the main factor affecting prices. The quality of the pipes used matters. If the installation is carried out by specialists, then the price of the work will depend on their qualifications.
An accurate calculation of storm sewers is the key to optimizing the estimate for such construction. After all, overly deep bedding and overly wide channels hit the customer's wallet no less hard than errors in the project.
Therefore, any storm sewer project starts with approximate calculations based on averaged geodetic and meteorological data, and finishes with cost optimization based on “local realities”. And in this article we will go from start to finish, touching on the subject of calculations and the methodology for optimizing the results obtained.
A typical project begins with the preparation of a technical task, in which all technical nuances are discussed, the results are announced and the cost of the work done is specified. The preparation of terms of reference for storm water is regulated by GOST 3634-99 and the relevant SNiP.
The next stage of the project is the calculation of storm water from tabular and "local" geodetic and meteorological characteristics.
And on this stage the following characteristics and parameters of the future conduit are calculated:
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- Type of storm drain design. At this stage, the design scheme of the storm sewer is determined (external or internal, deep or surface, and so on).
- Based on the scheme, the number and type of water collectors - storm wells or collectors (and the location of these elements relative to the foundation) are determined.
- According to the location of the water collectors, the footage of the drainage pipeline and / or storm trays is considered. Moreover, the footage is affected by the depth of the storm sewer, and the slope of the outlet channel, and the distance from the catchment point to the drainage well.
- In the final, the needs for shut-off and control and connecting fittings are determined, as well as the number and location of manholes.
Moreover, most of the parameters are affected by the calculation of water flow and the cross section of storm pipes, the magnitude of the slope and the depth of the laying, or rather the results obtained in the process of these calculations. Therefore, we will talk about such research separately.
Water consumption calculation
The calculation of the flow rate (volume) of water flowing through the storm pipes is the basis for all further research. After all, they are repelled from it when determining both the throughput and the diameter and the slope of the outlet pipeline. Moreover, water consumption most of all affects the estimated volumes of water collectors and collectors. After all, the entire volume of wastewater will be accumulated in these stormwater elements.
Well, the consumption itself is calculated by the formula:
V=q20 x S x D
Where V is the expense itself q20- this is a reference value indicating the volume of precipitation (in liters) falling on an area of \u200b\u200bone hectare (10 thousand square meters), S is the roof area converted from square meters to hectares (10,000:1), and D is the coefficient of moisture absorption by the foundation soil.
Moreover, both the volume of precipitation and the moisture absorption coefficient are indicated in a special collection of building codes (SNiP 2.04.03-85). Only q20 is displayed in graphical form, linked to the map former USSR, and D - in tabular form, with reference to the type of soil.
Calculation of the diameter of the storm sewer pipe
An accurate calculation of the pipe diameter is associated with very complex calculations, which take into account the roughness coefficient of the inner surface of the drainage pipeline, the velocity of the liquid flow through the pipe, the slope of the drain, and other quantities.
Therefore, in most cases, it is customary not to go into details, but to operate with the minimum possible diameters specified in SNiP 2.04.03-85. And in this standard it is mentioned that the minimum diameters of free-flow drainage networks are 200-250 millimeters.
It is this diameter that guarantees the optimal flow rate of wastewater in a free-flow pipeline - 0.7 m / s, thanks to which it is possible to ensure rapid disposal of wastewater of an average daily volume.
Slope calculation
Knowing the diameter of the pipe and the flow rate of the liquid, it is also possible to determine the minimum slope of the storm sewer, which guarantees the flow of liquid under the influence of gravity. However, in SNiP 2.04.03-85, these values are linked, first of all, with the diameter of the pipeline.
And for pipes with DN200 (nominal diameter 200 millimeters), the minimum slope is determined by a factor of 0.007. Moreover, pipes mounted to storm water inlets (drainage trays, storm wells, and so on) are laid with a slope of 0.02 (up to 2 centimeters per running meter of runoff).
Open drainage trenches filled with gravel (trapezoidal, 30 cm wide at the bottom and 40 cm deep) have a slope of 0.003. And the slope of the drainage trays ranges from 0.003 to 0.005.
Determination of bookmark depth
The minimum depth of laying the stormwater pipeline is determined based on several factors:
- Groundwater level.
- Soil type.
- Depths of soil freezing.
Ideally, the minimum depth of the bookmark should be less level groundwater and more soil freezing marks. That is, the storm drain will have to be deepened by 1.2-1.5 meters, if the groundwater level allows it. And this is only the “upper” edge of the drain, since the depth of immersion in the soil of the lower end is determined taking into account the height difference, according to the slope of the pipe.
Estimates for storm sewers: ways to optimize costs
A typical storm sewer consists of the following elements - water collectors, drainage pipes, sand collectors, intermediate wells (inspection and drainage) and a wastewater collection tank.
1. Moreover, the best results are shown only by a fully equipped sewer, in the design of which there are all of the above elements. Therefore, saving estimates by excluding any components is far from the best solution.
However, no one prevents us from combining some elements "in one bottle". For example, a manhole with a difference in nozzles can be turned into the same sand collector. And instead of trays - quite expensive products - use a perforated drainage pipe laid in a ditch filled with rubble.
2. In a word, there are a lot of options for combining functions. And each promises all tangible savings. In addition, it is possible to reduce the estimate by optimizing the size of sewage conduits or drainage wells. After all, the dimensions recommended in SNiP (200-250 millimeters) are suitable for industrial buildings and for entire blocks of one-story buildings.
3. But for a separate house equipped with a non-pumpable storm well, a 100 mm pipe is enough (a 150 mm pipe can be used to protect against flooding). The result is one and a half, and even double savings only on pipes.
4. Another way to save money is the already mentioned non-pumping storm well, buried to the horizon with high permeability. From such a well it is not necessary to pump out water or connect it to the central sewer. The drains will go away on their own, dissolving in sand that conducts moisture well.
As you can see, a creative approach to design gives a real chance for savings.
However, some arbitrariness is permissible only when arranging a household storm sewer, laid near a small summer cottage or a modest country house.
Really large buildings with a large roof or industrial facilities are best equipped with storm sewers, equipped according to the recommendations from GOST and SNiP. Otherwise, the owner of such facilities may pay a double price for their own indiscretion (and this is without taking into account the cost of dismantling an unsuitable storm drain).
This type of sewage is a complex engineering device, so the exact calculation of storm sewers during its design is of no small importance. In general, the installation of such a system requires an integrated approach; certain technical requirements must be observed in the process. The project must be approved by the Sanitary and Epidemiological Service, by the bodies for the protection of fish stocks and the protection and regulation of waters.
Stormwater design
Stages of drafting a project
The design process consists of the following steps:
- Storm sewer project: its development in relation to a specific site.
- Coordination of this project in all necessary instances.
- Direct implementation on site.
The first stage of the design is the development of project documentation. The basis for such work is the terms of reference, diagrams, drawings. When developing, it is necessary to rely on regulatory documents: SNiPs, SanPiNs, GOST 3634-99 and some others.
The main document at this stage is the terms of reference. It is compiled based on the wishes and requirements of the customer, filled in in accordance with GOST 19.201-78. The terms of reference reflect the terms of the work, the purpose of the device, technical and economic requirements, the control procedure. Applications are allowed if necessary.
Calculation of parameters included in the project
The methodology for calculating storm sewers includes the following key points:
- determining what type of sewerage should be used: internal or external;
- finding out the location of storm sewer wells, what will be their number;
- calculation of the required pipe length;
- selection of signaling devices, sensors and materials.
The decision is influenced by such parameters as the catchment area, the presence of water bodies (natural or artificial) in the immediate vicinity, the maximum amount of precipitation and the average rate of their precipitation, the speed with which runoff water moves and other factors that can characterize this object.
The calculation of water consumption and the cross section of storm pipes are described in the article "".
In order to have an idea of the monetary investment invested in the organization of this system, an estimate is made for storm sewers. It includes the cost of all components, namely:
- Point type water collectors.
- Water pipe systems.
- Various purposes of storm sewer wells.
- Effluent filters.
If necessary, the estimate can be supplemented with other elements at the request of the customer.
One of the important parts that the storm sewer scheme includes is a well. Depending on its type, it can collect wastewater, distribute it for treatment, water sampling, sediment erosion, flow measurement, inspection and maintenance of underground utilities.
The process of designing a rainwater sewer system has its own characteristics, which include:
- trace;
- calculation of hydraulic parameters;
- designing system elements, their linking.
Tracing is necessary in order to collect rain and melt water from a specific area and divert it to the place of release or treatment.
At what depth should storm sewers be placed
Despite the fact that this issue is being vigorously discussed at construction forums, SNiP 2.04.03-85 gives a clear answer to it, which states that the depth based on the experience of operating networks in this region is taken as the smallest depth.
Pro tip:
If there is not enough data, then the minimum depth of laying the stormwater pipeline for pipes up to half a meter in diameter is taken by 30 centimeters, and pipes with a diameter of more than half a meter are not less than 70 centimeters from the surface.
To determine the minimum depth, thermotechnical and statistical calculations are carried out.
For practical purposes, the depth of the storm sewer is such that it is possible to minimize the amount of work performed when digging a trench, as well as to ensure the pipes are safe from external damage and prevent freezing of sewage in the pipeline.
Storm slope
Pro tip:
To determine the minimum slope of a storm sewer, the type of drainage, cross-sectional diameter and surface coverage must be considered.
With an inner diameter of pipes of 0.2 meters, the slope should be 0.007, and if the inner diameter is 0.15 meters, the slope should be at least 0.008. If for objective reasons it is impossible to make such a slope, the standard is reduced to 0.007 for 150 mm pipes and to 0.005 for 200 mm pipes.
For open-type drainage systems, the minimum slope values for storm pipes are:
- for a drainage ditch - 0.003;
- tray of the roadway, the surface of which is asphalt concrete - 0.003;
- tray of the carriageway, which is covered with crushed stone or paving stones - 0.004;
- when the cobblestone tray of the roadway is covered - 0.005;
- separately located tray - 0.005.
Based on these numbers, you can see that the slope depends on the roughness: the larger it is, the greater the slope required. The diameter of the pipes also matters: the larger it is, the less slope is required to ensure the required flow rate.
Pro tip:
When constructing a drainage system on your own, it is best to use a "surface slope". The other two methods are applicable only if ready-made factory drainage channels are used.
The numbers given in normative documents, are the result of practical research in the construction a large number buildings, however, are not dogma for the developer. They provide the information needed to create a reliable system. If you adhere to these standards, then with the right one, it will serve uninterruptedly for many years.
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