During the construction of any engineering systems, the developer needs to look for compromises between effective working schemes and the cost of work. So when laying a sewage system in a private house, namely, calculating the depth of the laying, it is necessary to take into account such nuances as the level of freezing of the soil in a given area, the slope of the relief, the sewerage scheme (the presence and number of bends), the cost of land work. Guidance only by normative documents does not always give the desired result. So how to correctly determine at what depth the sewage system will work perfectly, but at the same time require minimal installation and maintenance costs in the future?
Why is this point so important
To avoid unnecessary clogging of pipes, it is recommended to arrange as few bends as possible and observe the recommended slope of the pipes, which will allow the waste to pass easily on its own. It is recommended that bends are avoided as much as possible and the pipes run directly to the treatment facility. But, as practice shows, this is not always realistic.
Note. If it is impossible to avoid bends, it is recommended to make wells at the joints. This will allow, if necessary, to get to the joints and clean them.
Depth standards and what affects them
To do this, you need to familiarize yourself with the established norms. These norms are contained in the document SNiP 2.01.01.82. It is here that you can find a map showing the depth of freezing for each region of the state.
So, thanks to this map, it is clear that in the Moscow region the soil freezes to a depth of 1.4 meters, while Sochi and other southern regions are only 0.8 meters deep.
It is worth noting that these norms are applied more for large objects, while private structures require different calculations. When laying sewers for housing, gravity systems are mainly planned, for the functioning of which a certain level of inclination is required:
- with a pipe diameter of up to 50 mm - the slope according to the regulatory document should be 3 cm per meter;
- with a pipe diameter over 50 mm - 2 cm for each running meter.
If these standards are not observed, the owner of the house may face the following problems: with a small slope, the waste will pass too slowly, which can lead to clogging of the pipes, and with a greater slope, the flows will be too fast, which will affect the life of the sewage system.
Another important point when taking into account the level of depth is what kind of structure will be at the end of the pipeline: so the deeper the pipes are located, the more a foundation pit will be needed. It is not recommended to deeply deepen the container - the lid should be at ground level. If you do not comply with this condition, then you will have to make a large throat for the septic tank.
Note.It should be borne in mind that the structure may fail and require repair, and the deeply laid system makes it difficult to access it, especially during winter periods.
Given these nuances, when laying a sewage system in a private house, you can not rely only on the depth of freezing of the soil.Moreover, there are arguments that allow you to lay pipes slightly above this level:
- The drains that pass through the pipes are at room temperature, and in some cases even higher. This allows the frost that forms inside the pipe to be washed away.
- If the sewage system is not used for a certain time, then the pipes will be empty, which means there is nothing to freeze.
- In a septic tank, heat is generated during the treatment and decay of wastewater, which penetrates into the drain pipes.
Based on this, it is possible to remove the pipe from the house slightly higher than the level of soil freezing specified in SNiP 2.01.01.82, and then be guided by the angle of inclination and the depth of the treatment plant.
Calculation example
So pipes in the Moscow region can be laid at a depth of 1.1 meters. But, if we assume that the skeptic is at a distance of 20 meters from the house, given the optimal slope level, which is 2 cm in this case, it is clear that the inlet pipe on the septic tank should be located at a depth of 1.5 meters (provided that the relief is even) ...
It is also taken into account that earthworks have their own cost and implementation period. In this case, it is impractical to lay pipes according to the norms of soil freezing. So for residents of central Russia, it is enough to lay pipes to a depth of 70 cm, since even in this case the system will function normally.
In addition, many people immediately insulate them when laying pipes, which allows them to increase their service life, thanks to protection from the external influence of the soil in which the sewage system is located, and also to maintain the temperature of the drains when they move through the pipes.
Conclusion
The installation depth of sewer systems depends on many factors. In this matter, it is not reasonable to be guided only by dry calculations according to regulatory documents. This can lead to additional installation costs and not increase the efficiency of the sewage system. When installing a sewage system in a private house, it is much more important to determine the depth at which the drains in the pipes will not freeze and the cost of excavation during installation. Moreover, the deeper the pipes are located, the more difficult it will be to get to them if it is necessary to replace or repair elements of the engineering system.
