The sewerage system is designed to drain contaminated wastewater outside the facility being serviced. In addition, this system must provide drainage of rainwater generated by precipitation and melting snow.
The structure of the internal sewerage includes:
1. Sanitary devices and receivers of sewage;
2. Bell pipelines;
3. Connecting shaped details;
4. Devices for network cleaning.
The sanitary device is connected to the internal water supply and sewerage networks, they are the main elements of the sanitary equipment of buildings. According to the purpose sanitary devices are installed: in bathrooms, washbasins, and showers (baths, washbasins, shower trays, ladders, bidets); in the premises of toilets and toilets (toilets, urinals; these devices are equipped with flushing tanks or taps); in kitchens (sinks). Special purpose sanitary devices installed in medical institutions, laboratories, baths, hairdressers, vehicles, etc. are also used. Materials for sanitary appliances are cast iron, ceramics, sheet steel, non-ferrous metals and alloys, plastics. Externally, the devices are covered with white or colored glass enamel (cast iron and steel), glaze (ceramic), or applied to them galvanic coatings (non-ferrous metal). Sanitary appliances are equipped with water-collecting or mixing taps, as well as siphons with water gates that prevent the penetration of polluted air from the sewer network into the room.
Internal sewerage is divided into three types:
K1 – household sewerage;
K2 – rain sewerage;
K3 – industrial sewerage (general designation).

Household sewer K1 is intended for drainage from plumbing fixtures, baths and showers, kitchens, public toilets and other premises.
The main elements of K1 in the course of movement of sewage of the internal sewerage:
1. Sanitary device;
2. Siphon (hydraulic shutter);
3. Drain pipe;
4. Sewer riser;
5. Diversion network in the basement.
At the end of the outlet pipe of the network should be provided for cleaning from a tee with a plug. Taking into account this cleaning, the length of the sewer outlet should not be more than 12 meters with a pipe diameter of 100 mm, according to DBN B.2.5-64: 2012.
It is also necessary to mention such an important element of the sewer as – fan (ventilation) riser. Its main task is to ensure the inflow of air into the sewer system, which ensures its ability to quickly cope with the transportation of large volumes of water and remove odors.
The height of the riser above the roof is taken according to DBN B.2.5-64: 2012 not less than the values:
z = 0.3 m – for flat operated roofs;
z = 0.5 m – for pitched roofs;
z = 3 m – for operated roofs.
The sewer riser can be arranged without ventilation, ie not displayed above the roof, if its height does not exceed 90 internal diameters of the riser pipe. Instead of a fan riser, it is also possible to install vacuum valves for sewer risers, which are installed at the level of the upper floor and perform the same function as the ventilation riser. Also, a vacuum valve can be installed on the discharge surface pipe to prevent the spread of odors in a particular room. But it is necessary to understand that for apartment houses the vacuum valve will be not enough and for such cases it is better to establish a fan riser.
In the rain sewer K2, to avoid the destruction of the roofing due to stagnation of water on the roof, on the roofs of houses install gutters: cap or flat. Drainage funnels, due to the slope of the roof, collect water that has accumulated from precipitation or melting snow and through the system of storm sewers K2, take it out of the house, providing reliable waterproofing of the roof.
The production sewerage K3 is intended for the removal of technological sewage from rooms. A distinctive feature of K3 from K1 and K2 is the presence of additional facilities: local treatment facilities (eg, grease traps), pumping stations, etc. For the production system of sewerage K3, it is desirable to make a separate outlet from the building (in a separate well from K1 and K2). This is due to the fact that industrial sewage K3 is considered “contaminated” compared to “clean” K2 and “conditionally clean” K1, and such wastewater must be pre-treated depending on the type of contamination.