Sewerage system is a network of pipelines, functional units, modules and standard components. The whole set is designed to ensure unhindered passage of wastewater. It is obvious that spontaneous movement of household wastewater in pipes is possible if the slope was observed during their laying.
From our article you will learn how to calculate the slope of the sewer. After all, this is not an arbitrary value: the slope should ensure the movement of effluents at the speed necessary for the normal operation of the system. We will describe how an important parameter for sewage is determined.
Sewer network device: rules and regulations
Installation of household and any other sewage system is quite clearly explained by SNiP. Moreover, the explanations available in the documents are the rules and regulations that professional builders strictly observe.
DIY construction, of course, is difficult to equate to professional activities. But this moment does not remove the installation obligations from the home master. Therefore, it is recommended that each builder know how to calculate the sewage system.
The construction of sewer communications in residential buildings is associated with the need for calculation. The main purpose of calculating sewage systems is to comply with permissible slope standards for pipelines and to comply with operating environmental conditions. Ignoring the calculations turns into serious problems
It would seem, why go into all the intricacies of the calculations? Is anything really going to change dramatically in the sewage system if we make the pipe slope a little less or a little more than the existing SNiP parameters?
So, the practice of operating communications shows: even small deviations of the values of the slope from the established norms can disrupt the normal operation of the sewage system.
For example, the owner of a private house makes a sewer with his own hands and does not own the calculation method. He takes and lays the slope of the pipelines “by eye”. As a result, the slope value of household sewage is less than the normative figures.
If during the sewage system in the house or at industrial facilities the pipe slope standards are not observed, the principle of self-cleaning of sewer networks is violated. This leads to periodic congestion, often unplanned cleaning of communications
The speed of movement of the economic and fecal environment decreases, at first insignificant congestion forms, followed by massive, difficult to break through. Finally, the line is completely clogged; the task of global cleaning is on the agenda. And such a system operation, with insufficient pipe slope, promises an enviable constancy of congestion and unpleasant odors.
Another point: an unprofessional master mounts the sewer at a slope that exceeds the normative figures. An overestimated slope of the sewage pipelines increases the speed of the liquid medium, but the so-called "separation effect" is formed.
Fluid flowing above the self-cleaning rate is separated from the solid mass that remains on the pipe walls. Over time, the residual masses increase, and the same result is obtained - mash, smells, cleaning.
Image Gallery
Photo from
The slope of horizontally oriented sewer lines is necessary for the implementation of spontaneous flow towards receiving equipment and unloading
Pipes with a slope are laid during the construction of internal branches of the sewer system and external lines that discharge drains to the points of treatment, accumulation or discharge
For home craftsmen who do not want to spend time on calculations, the construction standards provide for allowable biases, normal and lowest values are given
Sewer lines collected from pipes of Ø 110 mm are arranged with a normal and smallest slope, which should be 0.02 / 0.012. For pipes Ø 50 mm, the same values are 0.035 / 0.025
The standard and smallest pipe slope diameters of Ø 150 mm according to building directories is 0.01 / 0.007. The same values for pipes Ø 200 mm 0,008 / 0,005
The slope of the external sewer branches should be at least 0.02, that is, at least 2 cm per linear meter of the system
Laying drainage - perforated pipes that absorb groundwater in flooded areas are laid with a lower slope, from 0.001 to 0.003, so that the system has time to collect enough water for drainage
The slope of the drain of the sewer line should be 135º. If necessary, immediately after the withdrawal of the system from the house, a water lock is made of pipes of the same diameter as the pipeline
Slope of drain lines
Installation of external sewer branches
Line construction with pipes of different diameters
Example of laying sewer with a slope
Slope of large diameter sewer pipes
Slope of the external sewage pipe
Laying of drainage and storm sewer pipes
Sewer drainage slope
Correctly set slope values are the key to a long and reliable system operation.
About the calculation of sewer networks
The speed of movement of the economic and fecal environment, at which the self-cleaning effect is achieved, is mathematically calculated by the formula:
This mathematical formula is used to calculate domestic and industrial sewage. In particular, using the formula, the required slope of the sewer pipes is calculated
Designations:
- V - the velocity of the fluid, (not less than 0.7 m / s);
- H / d - filling of the sewer pipe (not less than 1/3 of the volume);
- K - resistance coefficient, depending on the material of the pipeline (0.5 - plastic, glass; 0.6 - others).
The workshop of household and industrial sewage systems allows situations when the conditions calculated by the specified formula cannot be fulfilled due to the low consumption of sewage.
In this case, it is recommended to mount communications from pipes with a diameter of up to 50 mm with a slope of 3 mm per 1 meter of length. Pipelines with a diameter of 85 - 100 mm are laid in compliance with a slope of 2 mm per 1 meter of length. In any case, the maximum allowable slope value can be 15 mm per meter of length, but nothing more.
If a channel mechanism for transporting sewage is used in the sewer system, there is also a standard for this case. So, the level of filling the trays should not exceed 0.8 the size of their height. The width of the sewer tray can not be less than 200 mm.
Moreover, the width of the tray is set based on the calculation of the hydraulic properties of the system and the design features of this element. So, sewer trays with a height of more than 500 mm in width should not be less than 700 mm.
The drainage channel system, just like the pipe system, is mounted taking into account compliance with the established standards for slope. In addition, tray systems are constructed taking into account the dimensions of individual line elements - depending on the size of the height and width
Trays in the construction of sewers are used in the construction of storm and drainage systems. An article, which we highly recommend reading, will familiarize you with the calculation of the slope of the drainage pipes.
Wastewater, filled with a high content of mechanical suspensions, is discharged along sewage lines made with a slope, the value of which is also determined by calculation, taking into account the provision of self-cleaning fluid velocity in the pipes.
Filling of pipelines is normalized by the value 1/3 of their volume. Typically, this type of effluent refers to industrial products, where particles of metals and other solids are mechanical suspensions.
Other norms (rules) of installation
The provisions of the regulatory documentation affect both the characteristics of the equipment involved in the sewer system, and the nuances of the installation itself.
Closed Communications Equipment
For most cases of designing household sewer communications, the norms (rules) provide for the execution of closed pipelines. Such a scheme traditionally works on the principle of the movement of household and fecal waters by gravity.
At some facilities (often industrial), where wastewater is discharged without odors and hazardous fumes, it is permissible to carry out communications based on gravity trays. In this case, it is required to equip the tray lines with a water lock device.
Laying of sewage pipelines is always straightforward. To create turns, bends, branches, additional mounting elements are used. From the initial point of installation of the line to its complete completion, it is necessary to withstand a uniform change in the slope according to the calculations
If we consider the system in plan, then each individual section of sewer communications is mounted strictly rectilinearly. If it is required to change the laying direction of pipelines, standard mounting components are used (corners, crosses, tees, transitions, etc.).
It is unacceptable to change the calculated values of the slope of the sewer pipelines in a separate section of the completed line, mounted in a horizontal position.
Image Gallery
Photo from
Formation of a slope of the external sewage system
Gasket from the exit to the unloading / cleaning point
Device openly laid branches
Concealed piping
Which pipes are suitable for the system?
In relation to sewage networks (domestic, industrial), as well as with an emphasis on the properties of corrosion resistance and strength, various modifications of pipes are used for the installation of sewage.
For communications made on the principle of gravity, pipe materials are:
- polymer compounds;
- cast iron;
- concrete;
- glass;
- asbestos cement.
Criteria and rules for choosing pipes for external sewage are given here. The information recommended by us will be useful to all the zealous owners of suburban areas planned for construction.
Under communications, transporting liquids with pressure, pipes are made of materials:
- polymers;
- cast iron;
- asbestos cement;
- reinforced concrete.
Sewer lines of internal action are mounted in one of two ways: open / hidden. Regardless of the installation method, polymer pipes are widely used in installation. The guidelines recommended by us will familiarize you with the guidelines for choosing the best pipes for sewage.
Sewer pipelines made of plastic may be laid in the ground below the floor level of buildings. But you should take into account the load per site with such communications.
The most common parts of sewer communications. Plastic pipes and all the necessary fittings are used in the construction of networks for various purposes. For owners of private real estate, this is an economical way to install sewage in the house
Plastic fittings are considered as universal, can be successfully used for internal and external networks.
Features of the installation of risers
Installation of risers inside residential buildings is done in canals, mines, boxes. Their design must comply with fire safety regulations. Mines, ducts, channels, etc., are necessarily equipped with removable panels.
Through the removal of panels provides access to communications. It is allowed to use removable panels made of materials capable of burning if the sewage line consists of polyvinyl chloride pipes. Panels of shafts where polyethylene pipes are laid are usually made of fireproof materials.
Open and closed lines
Installation of open sewer pipelines made of plastic is permitted inside the attic areas of residential buildings, as well as in basement areas.
The places where sewer risers move from the living area to the attic area must be covered with a cement mortar with a thickness of at least 20-30 mm. The same mixture protects the pipe region above the overlap level by 80-100 mm, and before sealing with cement, a waterproofing material is applied to the pipeline surface.
Laying of internal sewer lines is prohibited in the structure of floors, inside walls, in the ceiling area of housing stock rooms. A number of buildings and premises for other purposes fall under the same requirements, where a special sanitary regime is provided.
If it is necessary to lay a drain pipe from the sink of the bathtub or kitchen sink, this is done above the floor with the use of waterproofing, followed by facing the installation area.
Part of the home sewage system is the ventilation riser. It is an integral part of a professionally executed domestic sewage system. The norms for installation rules also apply to ventilation risers of domestic sewers. For example, stipulate the minimum allowable diameter of the pipes used.
The combination of domestic and industrial sewers is not allowed if industrial effluents contain liquids of a toxic nature or flammable. Sewer networks of any type, the scheme of which provides for the discharge of wastewater to the external sewage system, should be equipped with ventilation risers.
The upper ends of the ventilation pipes must be brought out through the thickness of the roof and raised to a height:
- For flat roofing (at least 300 mm).
- For pitched roofing (at least 500 mm).
The indent in the horizontal direction from the outlet of the riser to the nearby windows and balconies of the building should be at least 4 meters.
Sewer pipe laying
Laying a sewer pipeline with a slope is only part of the requirements for the general laying of a sewer network. You should also take into account the norms established for the laying of pipes, based on the risks of damage and destruction.
These standards are due to the effect of temporary and permanent loads on communications. For example, for domestic conditions, the laying of sewer pipes inside buildings is performed to a depth of at least 100 mm, if the surface of the floor and the upper outer wall of the sewer pipe are taken as the measurement points.
Pipelines of domestic domestic sewage systems installed in places of possible mechanical stress are recommended to be protected by restricting direct access to them. For these purposes, protective nets, trays, channels, etc. are used.
If the pipeline is located below the level of seasonal freezing of soil strata, the technology of warming sewer pipes should be applied. Rigid polyurethane foam completely claims for the role of modern insulation. Sewer pipes are also insulated with mineral wool with preliminary waterproofing.
One of the possible options for thermal insulation of the sewer line. Various materials can be used to insulate household sewage pipelines, but priority is always given to heat insulators with low combustibility or none at all.
When a trench acts as a place for laying communications, after developing one with an estimated slope and before laying pipes, it is recommended to perform soil compaction. Soil compaction works are carried out on the area of the bottom of the trench along its entire length.
Compacting the soil is required at least 200-300 mm in depth. After carrying out these measures, gravel is poured into the trench with an estimated slope or trays are laid and sewer pipes are already placed in the trays.
Interesting and informative reflections on the correct slope of the sewer pipe:
The organization of domestic waste water is not as simple a thing as an inexperienced layman can imagine. Professionals in the field of housing and household communications know: it is necessary to calculate the laying of sewer networks in each case of their construction, regardless of whether the installation is for a private house or an industrial system is being done.
Please write comments, ask questions, post photos in the block below. Tell us about how sewer lines were laid in your own suburban area, did you comply with the standard deviation. It is possible that your tips will be useful to site visitors.