Laying sewer pipes in the ground: technological rules and nuances

Nikolay Fedorenko
Checked by a specialist: Nikolay Fedorenko
Author: Lyubamira Lysyuk
Last update: March 2019

The construction of communications brings real comfort to the countryside, but their open location does not reflect in the best way on the aesthetic component of the site. It is quite another matter if the sewer pipeline is buried in the ground: it is not visible, the highway does not interfere with movement.

However, for the underground device of the system, compliance with the rules and regulations is necessary. They should be studied, agree?

The fundamental laws and subtle nuances according to which the laying of sewer pipes in the earth are presented by our site. Focusing on the information we have proposed, you will build a fail-safe external sewage system.

A pipeline constructed in accordance with our advice will work perfectly at any time of the year. The article presented to your attention scrupulously sets out the technology for the construction of the underground part of the sewer system.

The material describes the design nuances and laying details. Recommendations are given on the implementation of preventive measures and compliance with the rules for the operation of sewage. To simplify the perception of the information is supplemented with photo images and video instructions.

Features of autonomous sewage

Today, almost in every household there is a necessary set of amenities for a comfortable stay: wash basin, sink, toilet, shower or full bath, washing machine and other benefits of civilization. Many houses are equipped not with one, but with several bathrooms and bathrooms.

All this economy, when fully operational, produces a large amount of waste and wastewater per day. According to standards, the amount of liquid waste per day per person is from 5.4 to 9.5 liters, which must be merged somewhere.

Sewage system
As a rule, country houses where people live permanently have many different plumbing devices, which makes it necessary to equip an autonomous sewer system

Therefore, the drainage system is an indispensable part of the engineering communications of an individual house. It consists of domestic sewage, release from a residential building and an external sewer network laid on the site.

Many owners of private houses, paying particular attention to the internal house system, for some reason do not always properly treat the arrangement of external networks.

Indeed, the process of laying the pipeline seems simple, it is enough to dig a trench, dock the pipes with each other, the house system and the collector, and then fill it with earth.

But this is only at first glance. In fact, in this, as in any other work, there are many nuances that must be taken into account. Non-compliance with technological standards and improper laying of the pipeline may lead to siltation and other considerable problems in the future.

autonomous sewage of a private house
In order for the sewer system to function smoothly and for a long time, it is necessary to adhere to construction and technological standards when it is installed (+)

The drainage system should ensure the discharge of all wastewater, exclude the possibility of flooding the building in the event of an emergency, and guarantee the treatment of effluents when they are discharged into the water body.

When arranging the system, it is necessary to take into account such parameters as the material of manufacture and the diameter of the pipes, the type of soil in the area, the depth of the sewer pipes, a certain angle of inclination.

Autonomous sewage of private households can be made in the form of separate or joint removal and treatment. In the first case, two separate pipelines are made from the toilet for wastewater from washbasins, bathtubs and sinks and for fecal matter.

In the second case, all liquid and solid wastes are combined into one common stream and enter the septic tank, where they undergo a cleaning process, and then are exported.

Pipe selection for device

Previously, when laying sewers, only metal pipes were used: cast iron or steel. Indeed, these materials, like no other, are suitable for laying in the ground. They are strong, durable, have a low cost, easy to install.

However, along with the advantages, metal structures have significant disadvantages. The downside of steel lines is the possibility of corrosion, and cast iron pipes - a lot of weight.

cast iron sewer pipes
There is no equal in strength and durability to cast-iron pipes, this material can lie in the ground for decades without losing its qualities, but because of their severity, the laying of a water conduit is much more complicated

A certain difficulty is the sealing of the joints of a cast-iron pipe, as well as its inner surface, which, due to the characteristics of the material, will never be perfectly smooth. The latter characteristic affects the speed and quality of movement of waste within it, with time blockages can form in the pipe.

Asbestos-cement pipes can be used for laying sewers.They have a smooth surface, which eliminates the possibility of clogging, they simply connect using special couplings, their weight is much less than that of metal structures.

But they also have a significant minus - great fragility, which complicates their transportation and installation. Ceramic pipes have the same fragility.

Reinforced concrete structures have many advantages: they have exceptional strength, water resistance, and frost resistance. It is possible to make large diameter pipes from reinforced concrete, which cannot be made from other materials.

But the laying of such pipes is a big problem - because of their heavy weight, it is necessary to use special equipment, which is not always advisable in an individual farm.

Today, when arranging the sewerage of a private household, polymer pipes are most often used, which, for all their strength, are lightweight, which allows them to be laid by one person. They are very simple and easy to connect, with excellent tightness.

plastic pipes
For the arrangement of external sewage, orange polymer pipes are used. They have increased strength compared to gray pipes designed for internal piping, and also have the ability to withstand heavy loads

Polymer pipes come in three types - from polypropylene, PVC or HDPE (low pressure polyethylene). PVC structures, in addition to the above advantages, are also resistant to UV radiation and a slight change in parameters during temperature changes.

However PVC sewer poorly withstands very low and very high temperatures, and can also be deformed under mechanical stress.

The sewer system during its operation is subjected to dynamic loads that best withstand corrugated pipes. Even when freezing, the integrity of the trunk will not be violated, but deformation of its walls can occur.

The diameter of the pipes is selected based on the number of plumbing equipment installed in the house. So, for a country cottage with two toilets, 110 mm section pipes will be enough.

If there are three or more bathrooms in house building, it is necessary to use a pipeline with a diameter of 160 mm.

Rules and limits of system deepening

Some mistakenly believe that the deeper the sewage system will be located, the more efficient it will work. However, it is not. The system’s performance will not increase from this, the only thing that will increase is the cost of laying it.

In addition, the maintenance of the sewer network will become more complicated. And the biggest trouble can happen if, as a result of heaving or washing the soil, the pipes will not withstand its pressure and burst.

When laying sewer pipes, it is necessary to adhere to the norms and rules enshrined in SNIP 2.04.03-85. An important parameter that must be taken into account when installing the pipeline is the depth of its occurrence in the ground.

Despite the fact that the normative act does not provide clear parameters for the depth of the pipes, the document indicates which criteria are determining when laying the sewer line.

pipe laying depth
Usually in central Russia, pipes are laid to a depth of 0.8-1.4 m, which is quite enough for the effective functioning of the sewage system (+)

According to SNiP, it is necessary to be guided by the climatic conditions characteristic of the region, in particular, the level of freezing of the soil, and the experience of operating sewer networks in the area.

If there is no information about the operation of the sewage system, then the minimum depth of the pipeline should be 30-50 cm above the freezing level.

At the same time, there should be a distance of at least 70 cm from the surface of the earth to the top of the pipe. If the highway passes under a concrete platform or in places where vehicles are moving, the minimum recommended values ​​for the depth of the pipeline should be increased to 0.9-1 m.

In addition, when arranging the external network, it is necessary to take into account the material of the pipes and the composition of the soil, since the depth of freezing of different types of soil is not the same.

Clay and loamy soils in the same area freeze less than fine sand and sandy loam. Coarse and gravelly sand have the highest level of freezing.

freezing depth table
The table below shows how different the depth of freezing of different types of soil in the same city is.

Sewer pipe insulation

The efficiency and longevity of the functioning of the external sewage system largely depends on properly performed insulation. This is especially important in the northern regions and when the pipes are laid above the freezing level. To understand how important insulation is, you need to imagine how the system works in the cold season.

During the passage of the liquid, which always has a positive temperature, the pipe is partially filled with liquid effluents. Water vapor also fills the pipe.

In winter, at subzero temperatures, the part of the pipe that is closer to the surface is cooled, which leads to the formation of condensate, and then frost, which rushes to the center of the pipe, which often causes blockages.

sewer pipe insulation
The molded insulation is selected based on the diameter of the pipe, before laying the sewer line, it is simply worn on top

Avoid the formation of frost and blockages, as well as protect the system from freezing allows high-quality insulation pipelineand. It can be performed using various materials that are currently available in abundance on the market: foamed polyethylene, polystyrene foam, isover, thermal insulation and others.

Heaters are roll and molded. The first are wound on a pipe during its laying in the basement. A similar application is in a heat-insulating shell made of foamed polyethylene.

They are not used as thermal insulation of underground lines. Basically, molded heaters are used, which are made for a specific pipe diameter. Thermal insulation material of the required diameter is simply worn over the sewer pipe.

Heater for laying sewer pipes underground
One of the most popular heaters is Energoflex, which is made from extruded polystyrene foam. The closed structure of the material cells eliminates the penetration of groundwater, which can significantly reduce the insulating properties. Enhances foil cladding

If the temperature in the region is very low, then one insulation is unlikely to become reliable protection of pipes from freezing. In this case, a heating cable is usually used, which is laid on the outside of the pipe inside the heat-insulating material.

At using a heating cable you need to take care of the complete tightness of the joints so that moisture does not leak inside.

Slope formation for free flow

When laying the pipeline, it is imperative to provide for a bias towards the septic tank. According to technological standards sewer pipe slope with a diameter of 110 mm should be 20 mm per meter of pipe. Pipes having a diameter of 160 mm must be laid with an inclination of 8 mm per meter of the laid line.

pipe slope standards
When laying pipes, the slope is calculated per meter of pipe. The figure shows how much the difference between the sides of pipes with different diameters should be

The presence of a slope is a determining parameter for the successful functioning of the system. The closer the pipeline indicators to the normative ones, the more efficient the sewage system will work.

A complete lack of slope, as well as excessive slope of the pipeline, will lead to siltation of the system. In the first case, the waste will not be able to be transported through pipes at the required speed, which will lead to the formation of blockages.

In the second, the liquid will move too fast, which will ultimately reduce its transporting capacity, and waste will remain in the pipe, which will also lead to blockages and further siltation of the pipeline.

standard sewage slope
The slope of the pipeline should always be directed from the outlet from the apartment building towards the septic tank. This condition is especially important when using the non-pressure type sewers, which are often equipped with private households.

You can control the slope level of the entire trench using a special device - level. If the device is not on the farm, then the slope is checked using the building level.


  1. At the beginning and at the end of the pit, pins are driven into which the cable is tied.
  2. A building level is applied to one end of the rope and horizontal adjustment is made.
  3. The height of the trench is measured on both sides to the cable.
  4. Simple mathematical calculations are made.

For example, the total length of the trench is 50 m, a pipe with a diameter of 110 mm is used. From the side of the exit from the house, the depth of the pit is half a meter. In this case, at the end point of the pit, its depth should be equal to one and a half meters.

A detailed technology for calculating sewage slope is described in this article.

If the site has a natural slope that exceeds the recommended standards, you can lay a sewer with several vertical passages. In this case, on horizontal sections of the pipeline it is necessary to comply with regulatory indicators.

stepped sewage slope
In areas with a large slope, the pipeline can be laid in a stepwise manner. If the slope angle slightly exceeds the standards, they are limited to one vertical transition (+)

Another option is to lay a vertical pipe at a significant depth at the exit from the house, and already from it lay a pipeline with the desired slope. At the same time, the depth of the trench will be greater than when laying in the first way.

For the same purpose, you can use a differential well, falling into which, waste water flows smoothly to a lower level of the pipeline.

Pipe work

Technologically, the process of laying sewage is not particularly difficult. First you need to dig a trench, the depth of which corresponds to the normative indicators specific to this region.

Before laying sewer pipes, sand is poured into the bottom of the ditch. The height of the sandy base is 10-15 cm, so the depth of the trench should also be increased by these values.

laying a pipe on a sand cushion
Sand cushion allows you to align the bottom of the ditch. Sand must be carefully compacted before laying pipes to prevent subsequent shrinkage.

The width of the trench is laid about 40 cm more than the diameter of the pipe used. In the places where the pipes approach the septic tank and at the exit from the house sewerage, the trench is made a little wider so that it is convenient to carry out installation work.

Installation of septic tanks
To prevent the foundation and walls of the house from getting wet in case of emergency leakage, the septic tank is installed at a distance of no closer than 5 m from the building (+)

After the trench and the foundation are prepared, it is necessary to connect the pipes together, and then lay them. It is not possible for one person to lay long sections of the highway evenly and correctly, therefore it is advisable to involve several assistants in this work.

At the ends of the pipes are special sealing gum. Before they are docked with each other, a silicone plumbing lubricant is applied around the perimeter of the pipe, which facilitates the joining process and makes the joint more reliable.

But here you can’t use force, excessive force on the pipe can damage the gum or tear it from its seat, which will lead to a violation of its tightness.

Before laying the prepared pipeline, a nozzle is put on the outlet from the house drainage, which has the required angle. The other edge of the line fits into the hole in the septic tank.

If the storage well is made recently, it is advisable not to immediately close the hole with concrete, since the pipe may burst when the septic tank shrinks.

Sewer pipe
A pipe worn on the pipe leaving the house allows you to direct the pipeline in the right direction

Backfill of the sewer pipe is carried out as follows: first sand is poured so that the pipe is completely covered by it. Then it is poured with water, and after its shrinkage occurs, another batch of sand is added. After that, the highway is completely covered with earth.

According to technical standards, pivot wells should be installed in the places where the track turns, and on the straight sections of the pipeline, observation wells are equipped for every 35 m. In addition, every 15 meters of the direct highway, an audit or cleaning is established.

audit installation
Installation of the audit is a simple procedure, but it allows you to monitor the condition of the sewer network throughout the pipeline and, if necessary, clean the desired area with a cable or a stream of water

An audit can be done from the same sewer pipe, which is installed vertically in the desired sections of the pipeline using a tee. From above it is closed by a stub. With this fairly simple device, you can get quick access to a clogged section of the highway.

On the most critical sections of the network, it’s better to install manhole.

Actions for freezing sewers

If you have not insulated the sewer pipes, or insulated them insufficiently, and they have frozen, you first need to identify the damaged section of the pipeline in order to choose a method for solving the problem. Metal pipes can be heated using a blowtorch.

If the piping is made of plastic, open flames must not be used. You can pour hot water into the sewer, in which salt is previously dissolved (2 kg per 10 liters of water). You can direct a stream of steam or hot water in the revision closest to the frozen area.

If the damaged pipe is in the middle of the line, you can use a steam generator to warm the soil. However, this process can take quite a while. It is best to prevent freezing of the system, and when laying pipes to conduct their high-quality thermal insulation.

Conclusions and useful video on the topic

In this video, the installation process of the external sewage system is described in great detail, as well as the normative indicators that must be followed during installation:

This video shows how to lay sewer pipes in the ground:

Despite the apparent simplicity, the work of laying sewer pipes requires a competent approach and knowledge of the regulatory rules for laying. Only with the observance of the necessary indicators and the correct performance of work, it is possible to equip a truly effective and durable sewer system.

Trying to lay sewer pipes yourself? Or maybe they do not agree with the stated material? We look forward to your comments and questions - the contact form is located below.

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Visitors Comments
  1. Novel

    In his example, faced with a gasket, or rather, with the replacement of sewer pipes, he thoroughly learned the regulatory documents. He conducted pipes so to speak “by eye” according to the principle of the arrangement of the old ones. In fact, an insufficient angle of inclination of the entire line was obtained, which in the future led to unpleasant consequences and, ultimately, to alteration of the entire highway. Bad experience. The article revealed even more nuances. Not everything is as simple as it seems at first glance.

    • Valeichik

      Standards need to know. Also faced with this. We are building a small country house. Last summer, the team did us the laying of sewer pipes and everything else. But in the spring we were flooded. As it turned out, the pipes were initially of poor quality, which did not allow hermetically to connect everything. According to the popular saying “avaricious pays twice”, I had to redo everything all over again.