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During rainfall, a huge amount of water collects on the roofs of houses and roads. It must certainly be taken to a ravine or drainage wells, which is what storm sewers do. Many saw huge trays along the roads, covered with bars on top. This is the drainage system, but not all. A complete storm sewer device involves the use of several elements that form the main nodes for collecting water.
The device of the drainage system
The photo shows a diagram of a system that allows you to collect water from the roof of a building. This is only part of the drainage, because the drains then need to be put somewhere. The general scheme of storm sewers consists of the following nodes:
- storm water inlets;
- pipeline;
- drainage wells;
- filters.
Each node has characteristic varieties, and performs its role. Next, we will consider each element separately. So it will be easier to understand the principle of operation of storm sewers, as well as its structure.
On the video device of the drainage system:
rainwater inlets
Often this element of the drainage system is called a water intake. The essence of this does not change. The design is designed to receive rain or melt water. Hence the name came from. Rain inlets are produced in various sizes, shapes, depths, as well as from different materials. From above trays cover with a strong lattice.
RC trays
Concrete trays for storm sewers are used in road construction. Rain inlets are installed to collect wastewater in places where a lot of pressure is applied to the structure. Depending on the brand of concrete used, there are three types of reinforced concrete trays:
- Lightweight storm sewer trays are produced with a maximum wall thickness of 2 cm. The designs give a cubic shape. A light water inlet is mounted under the outlet of the downpipe from the building, and a plastic outlet is used as a connecting element.
- A heavy concrete storm water inlet is designed for a load of up to 3 tons. Such water inlets are installed along small roads, at sites where cars are expected to enter. The trays are made of fiber-reinforced concrete with a wall thickness of more than 2 cm. From above, the catchment structure is covered with a cast-iron grate with a galvanized coating.
- Main trays for storm sewers are distinguished by their collapsible design. The water inlet consists of several parts, which simplifies the process of its installation. The material for the manufacture of trays is reinforced concrete. The minimum wall thickness is 5 cm. Cast iron gratings are used to cover the trays. Reinforced concrete structures withstand heavy loads, so their installation site is motorways.
In private courtyards, when laying a drainage system, concrete storm water inlets are practically not used due to their large dimensions and weight, as well as the complexity of installation. And in road construction, reinforced concrete trays for storm sewers are gradually being replaced by more reliable cast-iron water inlets.
Cast iron trays
This type of storm water inlets is also used in road construction. The structures are made of SCH20 cast iron, which is resistant to heavy loads, as well as to the effects of aggressive impurities in water.
Depending on the shape and allowable load, cast iron trays produce the following modifications:
- Small storm water inlets “DM” are produced in a rectangular shape. One tray weighs at least 80 kg, and can withstand a maximum load of up to 12,5 tons. Small water collectors are installed in the yard near apartment buildings or along a non-busy highway.
- Large storm water inlets “DB” are designed for a maximum load of 25 tons. The trays are rectangular in shape and weigh at least 115 kg. The installation site is large highways, parking lots and other similar places with a large number of passing vehicles.
- Round-shaped storm water inlets “DK” are temporarily installed instead of rectangular trays when they are sent for repair. The design weighs approximately 100 kg, and is designed for a load of up to 15 tons.
From above, the trays are covered with cast-iron grates. For reliability, they are fixed with bolts.
Plastic water inlets
In private construction, plastic storm water inlets are the most popular. Their popularity is justified by light weight, ease of installation and long service life. Each type of plastic tray is designed for a certain load, which is indicated by the letter marking of the product:
- A – up to 1,5 tons. Storm water inlets of this class are designed for installation on sidewalks and other areas where vehicles do not drive.
- B – up to 12,5 tons. The tray will withstand the load from a car, so it is mounted in parking lots, near garages, etc.
- C – up to 25 tons. Water collectors can be installed at gas stations and highways.
- D – up to 40 tons. The grating of this storm water inlet can withstand the weight of the truck without any problems.
- E – up to 60 tons. Similar models of water intakes are installed on road sections and areas with a heavy load from vehicles.
- F – up to 90 t. Storm water inlets are designed for specially equipped areas for heavy equipment.
All plastic storm water inlets are made with a pipe down or to the side to drain water. The choice of model depends on the place of its installation in the drainage scheme. The top of the trays is covered with a plastic grill.
Composite water collectors
Two types of trays are produced:
- polymer concrete products are made of concrete with the addition of plastic;
- polymer sand trays are based on similar materials, but sand and additives are also used as additives.
Composite water intakes, according to their characteristics, have found their place between reinforced concrete and plastic trays. Unlike concrete storm water inlets, products made of composite materials are lighter, have a smoother surface, but can withstand less load. If we compare trays with plastic counterparts, then composite products from them are heavier, but stronger. From above, storm water inlets are covered with cast-iron or plastic gratings.
Metal water inlets
Metal gutters are not very popular due to the fact that the material quickly corrodes. To increase the service life of the storm water inlet, it is necessary that its walls be made of thick steel or stainless steel. This option is not profitable in terms of cost and high weight. If it becomes necessary to install a metal water intake, then cast-iron models are preferred.
Pipes for the drainage system
So, the collected water now needs to be diverted to a sewer or drainage well. For this purpose, pipes are used in the storm sewer system. They are also made from different materials. Let’s look at what kind of storm sewer pipe is, and in favor of which one to give preference to:
- Asbestos-cement pipes have been used in the last century, and still have not lost their popularity. Such a pipeline is corrosion resistant, quite durable, and has a low linear expansion. The disadvantage is the large weight of the pipe and its fragility, which requires careful transportation and installation.
- Metal pipes are the only way out if you need to lay a storm sewer in a site with high mechanical loads. The disadvantage is the complexity of the installation of the pipeline, the high cost and instability of the metal to corrosion.
- Plastic pipes are available with a smooth wall or corrugated. The fact that the drainage pipe is intended for outdoor laying indicates its orange color. Smooth-walled PVC pipes cannot be bent, so the installation of fittings is required at the corners. It is more convenient to use corrugated pipes for storm sewers because of their flexibility.
In private construction, preference is given to plastic pipes. They are lightweight, do not rot, are cheap, and are easy to install by one person.
sand trap
There are different types of sand traps for storm sewers, but they all perform the same function and have a similar device. The filter housing forms a container. Above its bottom there are through pipes for connection to the pipeline. The sand trap has a filter grid that traps solid particles.
The principle of the filter is simple. Water moving through the pipes enters the sand trap. Solid impurities under the influence of gravity pass through the grate, settling at the bottom of the tank. Already purified water comes out of the sand trap, and moves further through the pipes to the drainage well. Periodically, the filter is cleaned of sand, otherwise it will cease to cope with its duties.
Wells
The drainage of water from storm sewers goes to a ravine, a drainage well or to a sewage treatment plant. Drainage, intermediate and sewer wells have a simple device. In principle, it is a container of a certain size buried in the ground.
A complex device has a distribution well installed in the system to divert wastewater of different degrees of pollution. The design is a plastic container with one inlet and two outlets. The well is equipped with a neck, on top of which you can cover with a cast-iron hatch. There is a ladder inside to get down.
Flow distribution occurs according to the bypass principle. Dirty water enters the well through the inlet pipe. The outlet pipes are installed one above the other. Dirty liquid with heavy impurities is discharged through the lower outlet and sent to the treatment plant. Less polluted water leaves through the upper outlet, and through the bypass channel – the bypass is sent to a drainage well or other drain point.
To summarize
That’s all the main components of the storm sewer units. At first glance, the drainage system looks very simple, but it is not. Accurate calculations and proper installation are needed in order for the storm sewer to cope with the maximum volume of wastewater.