The device and principle of operation of the storm sewer. The purpose of the system elements and the rules for their selection. Installation of the structure. The cost of assembling the drainage system and parts for it.
Storm sewage is a system for draining water from the roofs of houses and the surface of land after rain and other atmospheric precipitation. The design is designed to prevent flooding of the territory and underground premises. You will find useful information on building a storm drain with your own hands in this article.
The device and principle of operation of the storm sewer
Storm drainage scheme
A large amount of water on the surface, which remains after rain, can cause many troubles: soil erosion, waterlogging, plant death, destruction of the building foundation, flooding of basements, etc. Such problems arise for various reasons: there is a lot of precipitation in this area; the site is located in a lowland or it is located in a flood zone. Troubles are eliminated by quickly draining water from the territory using the storm sewer at home.
To create it, the following details are used:
- Gutters, funnels, downpipes… They are necessary to collect water from the roof surface and direct it to storm water inlets.
- Storm water inlets… Products are designed to receive water from the roof or site. Prefabricated tanks are often equipped with filter elements: a basket for collecting large debris and a sand trap.
- Door pallets… These are containers for collecting water directly near the front doors.
- Pipes… They are used in underground utilities to move liquid to the place of collection or disposal. Indispensable in urban environments.
- Receiving trays… Details for collecting liquid from the surface of the earth and directing it to storm water inlets. Usually used by individual developers in rural areas.
- Sand traps… They are needed to separate a fine free-flowing mass from a liquid. They are installed immediately behind the storm water inlets, in places where water flows into the underground system. Without such filters, the sewage system will quickly clog up and fail.
- Revision wells… Elements of a closed storm sewer. They are used to clean the underground part of the system.
- Collectors… Designed for collecting water from several pipes and trays and combining streams. They are also built if it is necessary to sharply change the direction of the highway.
- Storage devices… They serve for temporary storage of rainwater collected from the site.
The storm sewer system is conventionally divided into two zones: water drainage from the roof and from the surface of the land plot.
The diagram shows the principle of operation of a storm sewer
It functions as follows. Roof rainwater flows into gutters along the lower edge of the roof covering. They are mounted with a slope towards vertical riser pipelines. Through them, the liquid enters the storm water inlets located on the ground directly under the risers. These elements are connected by pipes with trays into which water flows from the surface of the site. The collected liquid is discharged through the mainline into the central sewer, outside the site, into a ravine or pond. To prevent the system from clogging, the sewage system is equipped with sand traps to clear the loose mass and grates to retain branches, leaves and other large debris.
Storm sewers of houses differ from each other in the volume of water that can be passed through themselves, in design, and in terms of service life. There are these types of structures:
- Open system… Built on the surface of the ground. The structural elements are buried and concreted, and covered with gratings from above. The highway is very simple and the least expensive. It is easy to make it yourself without developing a project. An open storm drain is built in small private houses and is often used as an element of landscape decoration. During frost, such a system is inoperative. It can be built at any stage of the site development.
- Closed system… In such structures, there are storm water inlets into which the collected water flows through pipes or trays. From them, the liquid is directed to the disposal site. The elements of the storm drain are not visible, they are hidden underground. The cost of a closed system is quite large, so the decision to use it must be justified. It is recommended to build such a drainage system at the initial stage of the site arrangement.
- Mixed system… It includes outdoor trays and pipes laid underground. It is used in the case of a complex terrain of the site. It is often used for laying stormwater along the shortest path.
- Point system… Designed to collect and drain water from surfaces that do not allow liquid, for example, from the roof of a house or from a concreted area. Most often these are storm water inlets with a removable cover and the simplest garbage catchers.
- Linear system… It is created for a comprehensive solution to the problem - removing water from a large surface area and directing it to the place of collection or disposal. Consists of gutters, trays, sand traps and a coarse filter for collecting large debris. They are mounted along paths and platforms.
Read also about the features of the local sewage system.
How to make a storm drain?
The effective functioning of the device depends mainly not on the materials used, but on the observance of the installation technology. Consider the scope and sequence of work when creating a drainage structure for a site with a house. Before starting construction, it is necessary to create a system design and choose the right materials. We will talk about all stages of installation below.
Storm sewer design
In the photo, the storm sewer project
A storm sewer project is most often developed for private houses, if there is no central drainage system nearby. It must comply with the requirements of SNiP 2.04.03-85. In the process of work, the total throughput of the structure, the diameter of the main line, the number of gutters, the depth of laying the underground part, and the load on the system are determined. Storm sewer schemes are always individual, therefore, two identical structures cannot be found.
When designing a storm sewer, you will need the following information:
- Geological structure of the territory;
- Features of the construction of the roof of the house;
- Precipitation intensity over 12 months;
- The location of the external sewage main;
- Drainage area.
When calculating the storm sewer system, first of all, the amount of water to be removed is determined. It is calculated by the formula V = q20 * S * U, where:
- V is the estimated volume of the liquid to be removed.
- q20 is a reference value characterizing the intensity of precipitation in a given area. It is taken from SNiP 2.04.03-85 (Sewerage. External networks and structures).
- S is the area of the area to be drained.
- U - coefficient characterizing the water absorption of the surface material. Depends on the properties of the material forming the surface.
The table below shows the values of the U coefficient for different materials:
|Roof covering||1, 0|
|Asphalt concrete||0, 95|
|Cement concrete||0, 85|
|Crushed stone||0, 4|
|Crushed stone with bitumen||0, 6|
After determining the volume of the liquid to be removed, the pipe diameter and its slope are selected depending on the U coefficient. The parameters are determined according to the table:
|Slope, mm||Diameter, mm|
Most often, pipes with a diameter of 100-110 mm are used in the storm sewer of a private house. They will cope with the assigned task even after a very heavy downpour.
The slope angle of the track is determined according to special tables. Usually it is 2 mm / m for a pipe with a diameter of 100 mm. The slope of storm drains is also related to the distance between the storm water inlet and the place for water drainage. The longer the track length, the greater the difference between the beginning and the end of the track. To prevent the accumulator from getting too deep, you can reduce the slope of the line within the tolerance.
Selection of parts for the storm sewer system
When choosing parts for stormwater drainage, it is necessary to take into account their characteristics and application features.
On a standard land plot, it is recommended to use products of the class A15, B125, C250, D400, E600, F900. The markings characterize the strength of the products. The diameter for specific sewer systems can be determined using special formulas and reference materials in SNiPs, but they never exceed 15 cm. For storm sewers, pipes are not perforated.
It is allowed to use metal, asbestos-cement and plastic parts in structures, but the latter option is preferable. In winter, water can enter the system and freeze there in the absence of pressure. Plastic has a high coefficient of expansion, so frozen water cannot damage it. In the spring, the ice will melt and the product will return to its original shape.
Brief characteristics of pipes are given in the table:
|Pipe class||Permissible load||Application|
|A15||Up to 1.5 t||Used in places with light traffic. Installed on pedestrian and bicycle paths.|
|B125||Up to 12.5 t||Withstands the weight of a passenger car. Recommended for installation near the garage.|
|S250||Up to 25 t||Designed for the weight of a loaded truck. Recommended for installation near roads.|
Storm water inlets
Used to receive water from trays and gutters. They are selected depending on several factors - the volume of the incoming fluid, the area of the site, the relief, etc.
The shops sell factory-made plastic and cast iron containers. Metal tanks are more durable, but plastic tanks are superior in some respects: they weigh less, cost less, and are easier to assemble. The products are equipped with baskets, siphons and grates.
Plastic storm water inlets are produced in rectangular or cubic shape with a wall size of 30-40 cm. The partitions provide places for connecting pipes.
There are removable containers for collecting branches and leaves, making them easy to clean. More expensive devices are equipped with water traps. They keep the unpleasant smell of decomposing organic matter inside the sewer.
Products can be made with your own hands from bricks. Homemade structures must be plastered from the inside, and the bottom must be filled with cement mortar. As a storm water inlet, it is allowed to use concrete rings, preferably with a bottom.
They are used to remove sand from water. The standard device is a multi-section camera. The stream, passing through them, loses speed, and the sand settles to the bottom.
Stormwater drainage trays
Plastic gutters are used on the roof. In the ground sewerage, concrete products or plastic boxes with a length of 1 m are used. The second option is preferable, because plastic trays are not as massive and reliable enough.
For use in house areas, buy trays of class A, B, C, designed for different loads.
When choosing boxes, pay attention to the hydraulic section of the chute (DN), which should correspond to the diameter of the pipe supplied to the chute. For plastic gutters, it is 70-300. In the private sector, channels with a hydraulic section of 100-200 are usually used. To facilitate installation, the products are equipped with a locking system.
Revision wells, collectors
The dimensions of the products depend on the depth of the storm drain and the distance between adjacent buildings. With a well diameter of 150 mm, they are built every 0-35 m.In private properties, they are installed every 4-5 m.
The shops sell factory-made plastic wells. They are in the form of a cylinder with a sealed bottom and an open top. The walls are provided with flanges for connecting parts.
For temporary storage of water, large-capacity sealed plastic barrels or large-diameter pipes are used. The choice of a product depends on the preferences of the owner, but plastic containers are most often chosen. Modern accumulators consist of several sections, in which water is purified according to the same principle as in septic tanks.
Elements for connecting parts of the line
Couplings or fittings are selected depending on the material of pipes and trays and their design features.
The knees help change the direction of the track. It is not recommended to use pipes with an angle of rotation of more than 45 degrees in order to avoid clogging of the sewage system.
Stormwater drainage installation instructions
The drainage system consists of two parts: the system for collecting water from the roof and the ground section. Consider the sequence of installing the sewerage system in the house adjoining area (closed version).
The construction of the storm sewer begins after the development of the sewer project:
- Determine in which direction the roof gutters will slope. The water should drain in the direction from which it can be easily removed outside the site. Usually it is directed to the corners of buildings, where storm water inlets are placed, and underground highways are built from the side of the pediments. On a gable roof, the gutters should be located on the side of the slopes.
- Pull the cord so that it slopes towards the drain. Temporarily fix the grooves with a depth of 30-50 cm, guided by the cord. Fix them permanently to the wall with brackets in positions that provide an inclination of the trays of 4-5 mm / m.
- Collect the gutters through which water will flow from the gutters to the storm water inlets. Place a collection funnel at the top of the pipe.
- Install the storm water inlet under the gutter. Make sure the jet is flowing exactly to the center of the container. Otherwise, spray will fall on the walls and foundations of the house. Secure the tank with mastic into the previously prepared hole. After the mastic has hardened, cover all joints with sealant.
- On the surface of the earth, mark the sewerage route from the storm water inlets to the disposal site (storage, ravine, central sewerage, etc.). It must comply with the storm sewer scheme developed in advance. Hammer in the pegs in the locations of wells, sand traps, accumulator and other elements.
- Dig holes for large assemblies - wells, bins, trays, etc. Fill the bottom with a sandy pillow 8-10 cm thick. If tall trees grow nearby, cover the bottom with geotextiles so that the roots do not destroy the structure.
- Dig pipe trenches according to the markings. The depth of the ditch depends on the class of the product and the level of soil freezing. The stronger the parts, the lower they can be buried. For pipes with a diameter of 0.5 m, dig a trench of 0.5 m. Bury the lines of a larger diameter at 0.7 m. Compact the bottom and fill it with a sand cushion 8-10 cm thick. To reduce labor intensity, it is recommended to make the underground part short. The longer the above-ground open part of the storm sewer is, the more efficiently it will function.
- Install trays to collect water from the surface of the site in their regular places. Make sure that the paths near which they are installed have a slope, otherwise the water from them will not drain into the boxes.
- Install sand traps. They should be located behind storm water inlets and trays in places where the stream flows into an underground pipeline.
- Determine the feasibility of building collectors and carry out their installation. Revision wells are not needed if the structure contains trays for collecting water and storm water inlets with sand traps.
- Lay the pipes at the bottom of the trench at an angle towards the intake manifold and connect to the system elements.The slope of the storm sewer depends on the diameter of the line. It should not exceed 15 mm / m, and its minimum value is 2 mm / m. It is not recommended to tilt the line too much, because this can lead to blockages. At a high flow rate of water, sand is not removed and accumulates inside the products.
- When connecting the outlet pipe to the storm water inlet, slightly increase the angle of its inclination so that the liquid does not stagnate in the device. Decrease the slope in front of the sand trap to reduce the flow rate. This will improve the quality of water purification from sand in the device.
- After assembling the structure, make sure that the line does not sag.
- Install the container to collect the liquid. Work is performed if water cannot be removed outside the site. Dig a hole and place a layer of sand and gravel on the bottom to filter the liquid before soaking into the soil. It is allowed to direct water into the filtration field, which is formed next to the accumulator. Often the liquid is used to water the garden. The water from the storage tank must not be drained into the drainage system and septic tanks, because they will fill up quickly.
- Work on the installation of storm sewers ends with a check for the tightness of the structure. To do this, pour a certain amount of water into the storm water inlet and measure it as it flows into the reservoir. The volumes must be equal. If no problems are found, fill the ditch and cover the trays with grates.
- Provide a security zone near the sewer. Its dimensions are indicated in SNiP, but in most cases the boundaries of the site are marked at a distance of 5 m on both sides of the route. Any construction is prohibited on the allocated territory, you cannot create landfills and park cars. It is not recommended to plant trees with strong roots closer than 3 m from the pipe.
- After completing the installation of the storm sewer, check its functioning. To do this, direct a stream of water from a hose to the roof and surface of the site and make sure that the system is assembled correctly.
It is not difficult to build a storm sewer with your own hands, even if the blind area is filled with concrete. To do this, next to it, parallel to the walls, make channels of concrete or plastic with a slope towards the drain. Water from the roof and from all over the yard will drain into such recesses.