What is included in sewer networks. Snip external sewerage networks. Components of a pressure sewer network

External sewerage networks are located outside residential premises. The system is designed to drain wastewater and further purify it. Installation of an external sewer system is strictly regulated by regulations - SNiPs.

Classification of external sewer networks

External sewer networks, depending on the method of their organization, are divided into several types:

systems where household wastewater and rain or melt water are transported separately and to different collectors are called separate;
networks where rainwater and domestic wastewater are transported separately but enter a common collector are called semi-separate;
systems without dividing water into domestic and rainwater are called all-floating.

The most effective, from an environmental point of view, is a separate sewer system. It is more expedient to install the same sewer system for domestic needs on a personal plot.

Main elements of external sewer networks

The external sewer network is a complex structure. As a rule, it includes:

metal or polyethylene pipelines of various diameters intended for the passage of liquid;

for various purposes: for viewing, for rotating the system, for arranging level differences. In most cases, reinforced concrete is used for devices, but durable plastics can also be used;

collectors, which are large-diameter pipes into which water flows from the storm sewer network or domestic systems;
specialized . Installed in places where it is impossible to equip the passage of liquid by gravity;

various local types intended for primary wastewater treatment;

discharges of water into external sewer networks or into bodies of water, for example, ponds.

Do-it-yourself installation of domestic external sewerage

Installing sewerage: external networks and structures is quite simple if you adhere to the basic rules:

trenches dug for should contain a slope sufficient for gravity flow of liquid. If you do not comply with these standards, you will need to install additional pumping stations, which will complicate the work and negatively affect the cost of the system.
Before installing the pipeline, the necessary equipment is installed: local treatment systems, wells provided for by the project.
on a long straight section of the pipeline, the distance from one well to another should be at least 15 - 18 meters.
It is more convenient to start installing the pipeline from the last outlet pipe.
It is more expedient to connect pipes by welding into a socket.

If the above rules are observed, the sewer system will work flawlessly for a long time.

Sewerage project

Like many other types of construction work, installation of an external sewer network begins with a project. It is best to entrust such work to specialists, but you can develop it yourself.

At the first stage of design, it is necessary to establish where wastewater will flow in the future. These could be:

centralized external sewer network. To connect to this system, it is necessary to carry out work to collect the documentation established by law. This connection is considered the best;
special sealed wastewater storage tank. Such a system is periodically cleaned by machines, so it is advisable to install the tank closer to the fence and roadway for ease of access by equipment;
local treatment facilities for further use of water, for example, for watering a garden or for discharging treated water into the nearest body of water.

At the next stage, it is necessary to study the climatic conditions of the area in which the external sewage system is supposed to be located:

find out the depth of freezing of the ground, on which the depth of the network depends. If it is not possible to lay pipes and structures below the freezing layer, then you will need to purchase special insulation for pipes, for example, glass wool.

examine the terrain. Is it possible to install gravity sewerage on the site or will the use of pumping stations be required?
find out the type of soil and the level of groundwater. If the water is located close to the surface, then the possibility of laying pipes below the freezing depth is completely excluded. The type of soil affects the layer of protective cushion for the pipes, which is constructed from sand. If the site has heavy soils, then the protective layer should be larger.

At the last stage, some indicators necessary for the correct operation of the sewer network are calculated:

amount of wastewater. It is estimated that one person needs about 200 liters of water per day.
pipeline laying slope. According to SNiP requirements, for pipes with a diameter of no more than 200 mm, it is enough to make a slope of 2 cm for every 2 m of the pipeline.
the required volume of a septic tank for an autonomous sewage system. The average course of wastewater disinfection occurs within 3 days.

It is better to entrust the design of external sewerage to specialists. As a last resort, you can carry out design work yourself, strictly following the recommendations.

Sewage installation

Installing a sewer system is somewhat easier than designing it. You can do this work yourself. To do this:

trenches are dug for pipelines and designated structures. The minimum margin in dimensions should be at least 20 cm, which is necessary for the convenience of laying the network.

A layer of sand is placed at the bottom of all trenches.
structures are installed: pumps, treatment facilities, wells, and so on.
An external sewerage network is being installed.

pipelines are laid in trenches and covered with a layer of sand.

The soil is laid using the backfill method.

An external sewer network is necessary on a personal plot. This system of structures will allow you to preserve the ecology of the environment and, without additional effort, obtain water for watering garden plants.

It is necessary to design and construct sewerage networks and wastewater treatment plants in accordance with regulatory documents. At the same time, compliance with building rules (SR) and standards must be carried out not only by commercial and government agencies, but also by private individuals who independently carry out the drainage system from a private home. The laying of both external and internal sewer systems is regulated. Compliance with all standards and joint regulations will allow you to build a high-quality drainage system for your house or apartment, which will be insured against breakdowns and ineffective operation.

Not only the construction, but also the design of external sewerage networks and treatment facilities must be carried out in compliance with SNiP marked 2.04.03-85. At the design stage, these joint ventures will allow you to take into account various important factors that have a significant impact on the choice and design of the drainage system. Such factors include:

Geological conditions. The composition of the soil, its nature and properties have a significant impact on the parameters of the system. Here it is important to take into account the properties of the soil (sandy, clay or rocky), terrain and other characteristics.
When designing external sewerage, you need to take into account groundwater level.
Climatic conditions. How deep you will lay networks and treatment facilities depends on the depth of soil freezing. SPs make it possible to determine the depth of sewer laying in certain conditions.
Thanks to SP, specified in SNiP with the designation 2.03-85, the designer will be able to determine the characteristics of the network and treatment plant, which depend on the total number of people living in the house or settlement, the number of industrial facilities or other enterprises for which it is necessary to design a sewerage system.
With the help of norms and joint ventures This regulatory document can determine what kind of protection zone a particular water supply structure or water body should have. In addition, treatment plants and sewer networks have their own security zones that must be observed when selecting a site for construction.

According to SNiP with the designation 2.04.03-85, sewerage networks and treatment facilities must be made of materials resistant to aggressive influences and corrosion. To ensure that external and internal sewer networks last as long as possible, they are allowed to be made from the following materials:

polyethylene;
polypropylene;
polyvinyl chloride;
cast iron;
steel;
asbestos cement;
reinforced concrete.

As a rule, pipes made of asbestos cement and reinforced concrete are used where it is necessary to construct external networks of large diameter. In addition to them, the standards and SP in SNiP with the designation 2.04.03-85 allow the use of pipes made of ceramics and glass, but in reality this is very rare.

Important: there is an old and a new edition of SNiP marked 2.04.03-85. This is due to the fact that norms and rules are often adjusted, supplemented or changed. The updated document has made the necessary changes and adjustments, so it is always worth using the new edition of the SP.

Pipe diameters

The drainage system is made using pipes of different diameters. The diameter of the sewer network depends on the purpose, pipe material, location, slope, number of connected devices and many other factors.

According to SNiP marked 2.04.03-85, it is recommended to use the following pipeline diameters for drainage systems:

Street sewer networks are made of pipes, the diameter of which should not be less than 200 mm.
Drainage inside neighborhoods and courtyards is done using pipes with a diameter of at least 15 cm.
Rainwater must be drained through sewer pipes with a diameter of at least 250 mm. The same applies to all-alloy drainage systems.
Intra-apartment and intra-house sewer networks can have a minimum diameter of 50 mm (for drainage from a sink, bathtub, sink and shower) and 100-110 mm (for drainage from a toilet and arranging a riser).

Slope, speed and filling

By observing SP and SNiP standards with serial designation 2.04.03-85, it is possible to calculate the flow rate of wastewater and the filling of the pipeline. This calculation is required to be performed in order to prevent the possibility of overflowing sewer pipes and treatment facilities. Calculating the filling of the collector will allow you to avoid increasing water pressure, clogging the pipeline or increasing the speed of fluid flow.

To determine the minimum speed parameters and filling of sewer pipes in SNiP with the designation 2.04.03-85 there is table number 16:

For pipes with a diameter of 15-25 cm, the minimum speed is 0.7 m/s, and the calculated filling capacity is 0.6.
For a sewerage pipeline with a cross-section of 30-40 cm, the speed is 0.8 m/s, and the filling is 0.7.
Through pipes with a diameter of 45-50 cm, wastewater can flow at a minimum speed of 0.9 m/s with a filling of 0.75.
With the same filling of a pipeline with a diameter of 60-80 cm, the flow speed of the wastewater is 1 m/s. And for pipes with a diameter of 90 cm, the speed will be 1.15 m/s.
With a filling capacity of 0.8 in pipes with a diameter of 100-120 cm, the flow speed cannot be less than 1.15 m/s, for pipes with a cross-section of 150 cm - no less than 1.3 m/s, and for a pipeline with a cross-section of more than 150 cm - no less 1.5 m/s.

According to SNiP marked 2.04.03-85, it is necessary to observe the slope of the pipeline to organize a gravity system. If the required slope is not observed when organizing drainage systems, the pipes will become clogged.

When organizing an external drainage system, use the following pipe slope parameters:

Pipelines with a diameter of 15 cm must have a slope of 0.008. That is, for every meter of length, the excess of one end of the pipe over the other should be 8 mm.
Pipes with a cross section of 20 cm must have a slope of 0.007 - 7 mm.
For a collector and a socket with a diameter of 110 mm, the slope size should be equal to 0.02, that is, the excess should be 2 cm.
Pipes and collectors with a diameter of 5 cm must have a slope of 0.03, that is, the excess is 3 cm.

Important: the slope of the pipeline is directly related to the diameter of the pipe. The larger the cross-section of the pipe, the smaller the slope should be.

Requirements for elements of the sewer system

According to the standards and SP specified in SNiP with the designation 2.04.03-85, all treatment facilities and sewer systems must be designed in compliance with the following requirements:

Only corrosion-resistant pipes may be used. Steel products are coated with a special insulating material. If it is necessary to provide protection against electrical corrosion, cathodic protection is used for a certain section of the pipeline.
The base for laying external pipes must be selected in accordance with the characteristics of the soil. So, on rocky soils, cushions made of sand or gravel are used, on peat or silty soils, solid fixing bases are used. On other soils, the bottom of the trench is simply leveled and compacted.
If a pressure sewer network is being installed, then plungers, valves and outlets must be used.
Inspection wells are installed at intersections, bends and changes in slopes or diameters of the pipeline.
The size of the inspection well depends on the diameter of the pipeline.
It is mandatory to install rainwater inlets in low-lying areas, on long stretches of land and in the area of pedestrian crossings, in parks, at intersections and crowded places.

Treatment plants

When designing treatment facilities, it is also worth adhering to the standards from the specified SNiP. So, septic tanks must be located at a certain distance from the foundation of the house. It should be at least 5 m. The septic tank should be located at a distance of at least 10-12 m from wells with drinking water.

Attention: if sanitary gaps are not observed, treatment facilities can lead to contamination of drinking water sources in the event of depressurization of the structure.

When installing a septic tank, other regulatory gaps are also observed, which are specified in detail in SNiP. Here are some of them:

If there is no connection between the layers of soil under the septic tank and the well or borehole, then a gap of 20 m can be maintained.
If filtering soils (sandy loam, sandy soils and loams) are detected, this gap must be increased to 50-80 m.
From the septic tank to a source with standing water you need to retreat at least 30 m.
Near a river or stream there is a 10-meter protective zone where septic tanks cannot be located.
Water supply networks must be located at least 10 meters from the septic tank. If the treatment plant is depressurized, contaminated wastewater will not be able to get into drinking water.

Important: any treatment facility must be located lower in the terrain than a well or borehole.

If there is a road with heavy traffic near the treatment plant, then the septic tank should be built no closer than 5 m from the road.
The septic tank can be located at a distance of 2 m from the usual passage.
Treatment facilities should not be erected closer than 2 meters from the boundaries of the site.
At least one meter should be set back from the foundations of outbuildings to the septic tank.
The septic tank should not be placed at a distance of less than 3 meters from trees. And bushes can be located no closer than 1 m from the treatment plant.
If a gas pipeline runs near the treatment plant, then a protective zone with a radius of at least 5 meters is made from it to the structure.

Correctly completed design and installation of external sewerage networks determines the duration and quality of their operation. The basic provisions and rules for the construction and repair of an external sewer network are determined by SNiP 2.04.03-85. The document regulates the full cycle of work on the installation of an engineering system, from pipeline installation to construction of treatment facilities. SNiP sewerage external networks and structures will help you select the optimal material and build an effective system for draining wastewater and rainwater.

What is external sewerage

External sewerage includes branched pipelines and system elements necessary for transporting wastewater from residential buildings and other facilities to treatment facilities. The design of the utility network is carried out simultaneously with the preparation of water supply plans. The systems are interconnected by the need to maintain a balance between water consumption and disposal. Installation and maintenance of urban external sewerage is the responsibility of public utilities. The maintenance of autonomous sewage systems in private houses is carried out by the owners themselves.

There are two ways to transport wastewater:

non-pressure or gravity;
pressure, requiring the installation of pumping equipment.

Types of sewerage

To ensure the safe operation of external sewage systems, SNiP offers several methods:

duplication of communications - providing the ability in case of an emergency to switch the flow to a parallel pipeline or channel;
reliable power supply, availability of an alternative (backup) source;
allowing for reserve when designing network capacity

Attention. When installing sewerage structures, a certain sanitary zone must be observed to the construction sites of residential and public buildings.

Structural diagrams

According to SNiP, external sewerage is divided into several systems according to the installation method:

All-alloy - according to this installation scheme, all wastewater - domestic, storm, melt - is directed into one sewer collector or container.
Separate - the system is designed so that household wastewater and melt (rain) water are transported through different pipelines and end up in various treatment facilities or storage tanks.
Semi-separate wastewater and storm sewer are sent through different mains into one container.

All-alloy scheme

Attention. It is prohibited to discharge wastewater into water bodies that has not been treated to established standards.

Classification of sewer system

External engineering communications are installed in various places and have their own purpose.

Yard network – used to serve one building. It consists of the following elements: small diameter pipes (150 mm), building outlets, intake and inspection wells. This concept is used for a system connected to a central sewer system; it is not used for an autonomous system.

Yard network

Intra-block network - the network is arranged inside the block, it consists of the same elements as the yard network.

The street network is designed to transport wastewater collected from all neighborhoods. Such a pipeline is called a collector; its function is to collect wastewater and discharge it to a pumping station or treatment plant.

Attention. Ground laying of sewer pipelines in populated areas is not permitted.

Schemes of drainage networks

Depending on the characteristics of the terrain, one of the external drainage schemes is selected:

perpendicular - used for rainwater sewer collectors to quickly transport water to the general flow;
zone - a rare option, applied to objects with a significant difference in height; a pump is installed in the lower collector;
cross-section - the main collector is installed along a river or other body of water to intercept wastewater;
radial - wastewater is directed to various treatment facilities.

Components of an external sewer system

The utility network consists of several main parts:

Pipeline is a pipeline made of pipes of various lengths and diameters, laid with a slope.
Wells - structures vary in purpose, they are: drainage, inspection, differential and rotary. The wells are equipped with brackets for lowering repairmen and hatches with covers.

Pipeline and well
Outlets into water receivers are elements that ensure the free exit of wastewater from the pipeline into the reservoir.
Collectors are underground tunnels in the form of large-diameter pipes (from 2000 mm), through which wastewater is transported to the end point of the network.

Collector
Local treatment facilities are installations used for treating and discharging wastewater into water bodies. These include septic tanks, biological treatment stations and other equipment. The number of houses served depends on the size and capacity of the structure.
Pumping stations - installed at individual facilities that require a dosed supply of wastewater.

The choice of method for disposing of domestic wastewater and rainwater depends on a whole list of factors that are taken into account at the design stage:

properties and nature of the soil;
climatic features such as freezing depth;
volume of transported wastewater;
groundwater level;
distance from the point of release from the building to the treatment facility.

Attention. The lowest permissible pipeline slope depends on the minimum sewer flow rate.

Selection of material for the pipeline

The materials used for the installation of lines and channels must be resistant to aggressive environments and the effects of abrasive particles contained in the liquid. To prevent gas corrosion of the upper part of the collector, ventilation is installed to prevent gas stagnation.

SNiP for external sewerage provides for the use of pipe networks made from the following materials for installation:

polyethylene;
polyvinyl chloride;
polypropylene;
steel;
asbestos cement;
cast iron;
reinforced concrete.

Polymer pipes

Cast iron pipes

Reinforced concrete pipes

In rare cases, when installing a network, pipes made of ceramics and glass are used; such materials are allowed by the rules.

Polymer products are the best choice when installing external utility networks. They have all the qualities that ensure reliable and long-term operation of the system:

resistance to mechanical stress;
frost resistance;
high throughput due to smooth surface;
corrosion resistance;
durability.

Rules for installing sewer networks

Pipe diameter

The capacity of the free-flow network depends on the size of the pipes. Building codes determine the minimum diameter of gravity pipes:

street network – 200 mm;
autonomous sewerage – 110-150 mm;
intra-block – 150 mm;

The size of the rain and all-alloy street system is 250 mm, the intra-block system is 200 mm.

Speed

SNiP presents tables that determine the speed of movement of wastewater depending on the size of the pipeline or tray. These indicators help to avoid silting of sewer networks. The flow contains suspended particles, which, if the speed is insufficient, settle on the surface of the line.

Basic calculation data:

diameter 150-250 mm – 0.7 m/s;
600-800 mm – 1 m/s;
more than 1500 mm – 1.5 m/s.

The lowest speed of movement of clarified waste through trays and pipes is 0.4 m/s. Maximum wastewater transportation speed:

through metal and plastic pipes – 8 m/s;
for concrete and reinforced concrete – 4 m/s.

For rainwater drainage, the indicators are:

metal and plastic pipes – 10 m/s;
concrete and reinforced concrete – 7 m/s.

Pipeline slope

One of the basic rules when laying a pipeline is compliance with the slope norm. For systems where the fluid moves under the influence of gravitational forces, this parameter is critical. The negative consequences of installation errors in the direction of decreasing or increasing the slope lead to improper functioning of the network, blockages and breakdowns.

Attention. The standard indicator is calculated per 1 linear meter of pipe.

For autonomous sewerage pipes that are smaller in size than central networks, the following standards apply:

In special conditions related to the terrain, a decrease in slope is allowed:

pipes 150 mm up to 0.008;
pipes 200 mm up to 0.007.

Storm water inlets are connected to the general system with a slope of 0.02.

Network depth

The minimum depth of the sewer pipeline depends on the thermal engineering calculation. The practice of operating utility networks in the area is also taken into account. The pipes are laid 0.3-0.5 m below the freezing point of the soil. The maximum depth depends on several factors:

pipe material;
type of soil;
pipeline diameter;
laying method.

Requirements for wells

Wells are an integral element of the sewer network, therefore the norms and rules for their installation are described in SNiP.

Manholes

To inspect the pipeline, special elements are installed - inspection wells. Their installation is carried out in two cases:

at pipe joints;
at the section where the direction of the pipeline changes.

SNiP determines the diameters of wells depending on the size of the pipes:

main line up to 600 mm – well 1000 mm;
pipeline from 700 mm and more - pipe size + 400 mm in length and 500 mm in width.

Inspection well

On straight sections of the gravity network, inspection structures are located every 35 m, for medium-diameter mains (500-600 mm) - 75 m, for large pipes (1500-2000 mm) - 200 m. The working part of the structure is equipped with a hanging ladder for descent.

Storm drain

Storm drainage serves to quickly drain rain and melt water. It can be open, closed or mixed. An open network consists of trays and channels, a closed network consists of stormwater inlets and an underground pipeline, a mixed network is a combination of pipes and trays. To reduce the length of the system, the discharge is carried out into the nearest body of water or ravine.

When installing rainwater drainage systems, it is necessary to provide for the installation of structures for cleaning the most contaminated wastewater generated during rainstorms. For this purpose, sand traps, sedimentation tanks and filters are installed. It is also recommended to design the possibility of using purified rainwater for irrigation and industrial needs.

Wastewater treatment devices

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The smallest depth at which a street sewerage network can be laid can be determined by taking into account the possibility of connecting to its system the longest line of the intra-block network with a slope of 0.007. The smallest depth for laying the initial elements of the intra-block network is taken to be 30 cm less than the depth of soil freezing and not less than 50 cm from the surface.

If the sewer network becomes clogged, it must be inspected, flushed and cleaned. To do this, inspection wells are installed wherever there are changes in the diameter and slope of the pipes, where there are turns, and on straight segments of a sewer line that has the same diameter. In places where rivers, ravines, railway tracks, etc. intersect with the network, overpasses or siphons are installed. Dykers are made of metal pipes and are laid at the bottom of a ravine, river or under railway tracks. Dykers operate under the natural pressure of flowing wastewater. Overpasses have the form of a bridge covering an obstacle, along which a sewer pipe with a rear slope is laid in a protective box.

Flushing the sewer network from sediments constantly forming at the bottom of sewer pipes (in areas where the flow rate of wastewater is insufficient) is carried out by accumulating incoming wastewater in inspection wells (the lower hole of the well is closed with a portable shield) and quickly emptying them into the sewer network (when the shield is opened ). Thanks to these actions, a high speed of water movement is created, with the help of which all accumulated sediment is removed.

If a section of the network has an insufficient influx of wastewater, then the inspection well is filled with water through the fire hose of a hydrant located in the water supply network. In some cases, special flushing wells with a capacity of up to 2 m³ are installed in the initial sections of the network. They are filled with water from the water supply and connected to the sewer line.

Creation of a small sewer network for individual developments

Tools and materials needed to create an individual sewer network: digging tools, pipes, crushed stone, sand, tees, oblique crosses, tow, measuring instruments and tools for plumbing work.

During the construction process, it is necessary to take into account a number of sanitary and hygienic requirements and provide the opportunity to remove wastewater from toilets, sinks, washbasins, showers, bathtubs, etc.

To receive wastewater in all rooms on the site, sewer pipes with a nominal diameter of at least 25 mm are used. All pipes and fittings for the installation of an internal sewage system must comply with all technical conditions and meet sanitary standards.

July 18, 2016
Specialization: Capital construction work (laying a foundation, erecting walls, constructing a roof, etc.). Internal construction work (laying internal communications, rough and fine finishing). Hobbies: mobile communications, high technology, computer equipment, programming.

It's no secret that I'm going to build a dacha house for my son in the near future. And now I’m designing engineering communications for the future structure. In particular, external sewerage is on the agenda.

The design of this system, although it seems quite simple, especially in comparison with branched pipelines laid inside the house, has many nuances. Violation of certain requirements can lead not only to system inoperability, but also to dangerous consequences for others. And then the estimate should be smaller, because after all, I’m going to spend my own money, not government money.

In general, we had to tinker a lot. But as a result, I can provide you with detailed instructions on how to properly design and install this system with your own hands. Read carefully.

Building code requirements

First, let’s look at what external sewerage is according to SNiP. After all, you don’t want your future home to not comply with the established standards and not be accepted for operation by the relevant services. So I don’t want something like this for my offspring’s dacha, so I’ll dwell on covering the issue raised in more detail.

Elements of external sewerage

The external part of the wastewater removal system is necessary for transporting sewage to places of their processing and cleaning them from various contaminants.

It consists of several elements:

Pipelines of various sections and lengths. They are made from different materials and serve to deliver wastewater from the drain pipe of the internal pipelines of the house to treatment facilities (centralized or autonomous).
Wells. They are an essential part of the sewer system and are necessary to perform certain actions.

In my practice I have encountered the following types of wells:

to inspect communications (they are used to clean clogged pipes);
for arranging pipeline turns;
for laying pipes with height differences;
drainage

Collectors. They are unique pipelines of huge diameter that serve to accumulate and transport sewage water in centralized wastewater disposal systems.
Treatment plants. There are central (for a settlement or part of it) and local (used to clean sewerage in a private house). In the latter case, the treatment facility can be replaced by a storage tank, which is periodically emptied using sewage disposal equipment.

Swap stations. An intermediate link in the treatment system that accumulates wastewater and gradually delivers it to the treatment plant. Such units are used in centralized networks or privately if a biological treatment station with aerobic bacteria is installed on the site.

Above I have listed the main elements of the system. But to install an external sewer network, you will need many more materials and tools, which I will talk about below.

polymer - polypropylene, polyethylene, polyvinyl chloride;
steel and cast iron pipes are an outdated option, since the price of such parts is high, and the performance properties leave much to be desired;
asbestos-cement and reinforced concrete channels - used only in centralized sewers; I have not seen them in private houses.

I’ve also heard that there are pipes made of ceramics and glass, but I haven’t seen them in practice, so I can’t tell you anything specific. But this is a very exotic material, which is certainly not useful in private construction.

General installation rules

Regardless of size, performance and other parameters, when creating local external sewage systems, it is necessary to adhere to certain sanitary and construction rules.

The regulatory documents contain a lot of information, but for an ordinary craftsman doing sewerage in his own country house, it is enough to take into account the following factors:

groundwater level at the site;
soil properties;
the climate of the area in which construction is taking place;
the average volume of sewage that is planned to be disposed of per day;
the distance from the house to the central sewer collector or autonomous septic tank.

One of the main requirements that must be strictly observed (otherwise your external sewage system simply will not work) is the slope of the pipelines. The specific value depends on the diameter of the parts. To make it more clear to you, I have compiled a small table.

Before starting work on creating an external drainage system, I advise you to order survey work to study the soil, lay out the pipeline route, calculate the necessary parts and the cost of the work.
If you don’t want to do all this, at least ask for advice from those neighbors who have already completed work on arranging utility systems.

Requirements for external piping

Before choosing a specific type of pipe and starting work, I want to list the most important requirements that apply to external sewerage systems (they are enshrined in SNiP number 2.04.03-85):

The outer part of the sewer system must be constructed from materials that have the longest service life and are not subject to corrosion. After all, it will be operated in very aggressive conditions.

When laying pipelines, it is necessary to take into account the nature of the soil in order to avoid soil shifts after filling the parts. Otherwise, a leak will occur, which can become a source of groundwater contamination.
In the design of an external drainage system, it is necessary to provide for the presence of mandatory elements: inspection holes, valves, pipes, pumps, and so on. Believe me, all the rules were created for a reason, and you will greatly regret it in the future if you cannot clean the pipes due to lack of audit.
It is imperative to install inspection wells and hatches in places where pipes turn, where individual pipeline threads intersect, and where revisions occur. Otherwise, in the event of an accident, excavation work will have to be carried out. Wells must have safety elements (hatches, fences, ladders, etc.).

Construction of external sewerage

So, let's look at how external sewage is made. I divided all the arrangement work into several parts. But remember that specific instructions depend on whether you are connecting the pipelines in the house to a central sewer or building your own treatment plant.

But first things first.

Pit preparation

Installation of external sewerage begins with preparing a pit, or more precisely, a trench for laying pipes. You can dig it simply with a shovel (if the length is not very large) or order an excavator.

The depth of the hole directly depends on the depth of soil freezing in the area where you live. External sewerage pipes must be laid 50 cm below this mark. You can find the necessary information in special tables.

The approximate depth of soil freezing in different regions of Russia is:

in the northern regions of the Russian Federation - from 3 to 3.5 meters;
in the middle zone of our country - from 2.5 to 3 meters;
in the southern regions on the Black Sea coast - from 1.2 to 2 meters.

The values given are approximate. This is why I recommend conducting a soil study in the area where your house is built.

Most often, pipes with a diameter of 110 mm are used for installation of the external part of the sewer system. For them, I recommend digging a trench 60 cm wide (to make installation convenient). Depth – freezing level + 50 cm according to SNiP + 10 cm for the installation of a shock-absorbing cushion.

In addition, when digging a ditch for laying sewer pipes, I pay attention to several other features:

I always carefully level the bottom of the recess and make a slope, which I already mentioned above. It is necessary to ensure free flow of water towards the collector or its own treatment plant.

Once I have leveled the bottom, I carefully compact the soil below to avoid shifts. Then I pour a 10 cm thick sand cushion on top, which I also compact very carefully.
The fact is that the pipes are assembled using sockets, so soil shifts can lead to depressurization of the system. But I, for example, don’t want to dig up three meters of earth again to find a leak. Moreover, you will have to dig along the entire length.
In those places where the pipe enters the collector or, you need to make a wider platform (at least two meters), the bottom of which must also be carefully compacted and covered with sand.

The sockets and fittings are slightly larger than the pipe itself. Therefore, in the places where they will be installed, I always make pits so that the central axis of the pipe is always at the same level (naturally, with a slope from the house).

Pipe laying

Having finished with the hole, you can safely move on to laying the pipes. However, before that I want to say a few words about choosing the right material.

I will not mention citywide networks now, since large companies are involved in their construction. And for a private house or cottage, in my practice I used polymer pipes:

polyethylene;
polypropylene;
polyvinyl chloride.

If pipes will be laid at very great depths or this section of soil will be subject to frequent and significant dynamic loads, it is better to buy high-strength corrugated pipes made of polyethylene or propylene. They are joined together using shaped parts.

In all other cases, I use polyvinyl chloride pipes with sockets. If you have designed an internal sewer system, then you know what I mean. Just take not the gray parts that are familiar to you, but those varieties that are painted orange.

They are quite durable, have a smooth internal surface and are perfect for constructing external engineering wastewater disposal systems. The maximum that these pipes can be buried is 3 meters, which is quite enough for most cases.

I lay the pipes according to the following scheme:

First, I lay out all the pipes at the bottom of the trench without trimming. I put revisions, tees, crosses and other necessary shaped parts in the right places.
Then I begin the assembly, which I start from the inlet pipe of the collector or local septic tank. To do this, I take the parts cut to the required size and clean them of dust and dirt.

If you are cutting pipes with a saw rather than a pipe cutter, the end of the part must be cleared of burrs and a small chamfer removed, otherwise the rubber O-ring may be damaged. I also recommend making sure that the cut is positioned exactly at an angle of 90 degrees relative to the surface of the pipe.

After cleaning, I insert the smooth part of one pipe into the socket of the other until it stops. To provide an additional seal and extend the life of the seal, I always coat it with silicone sealant.
I proceed in the same way with the remaining parts along the entire length of the pipeline.

I would like to give one free piece of advice. If the external sewer piping design involves sharp turns, do not use 90-degree angles. It is better to install two at an angle of 45 degrees. And be sure to install a well with an inspection in this place.

This will save you from trouble and allow you to quickly clean a difficult area if it happens.

In this way, you need to assemble all the pipes into one system and test them for leaks. To do this, you need to pour a bucket of water into the pipe of the internal sewer system and wait until it enters the central collector or your own septic tank (more on that a little later).

Insulation

Very often, when constructing an external sewer system, I resorted to additional insulation of the plastic pipes used. Strictly speaking, if you have dug a trench of sufficient depth (below the soil freezing level), there is no need for insulation, but, as they say, it is better to be safe.

The following can be used as thermal insulation material:

glass wool or basalt fiber;
polystyrene;
polyurethane foam;
heat-insulating.

I advise you not to rack your brains over the choice of material and buy insulating shells made of extruded polystyrene. It has a fairly low thermal conductivity coefficient, high water-repellent properties, long service life and increased strength.

Among other things, to install it on pipes you do not need to resort to any tricks. It is enough to mount the halves of the shell on the pipe and snap them onto special locks, wrapping them with adhesive tape on top to be sure.

This is much easier than wrapping pipes with mineral wool, then securing it, then wrapping roofing felt on top, and so on.

Backfill

The last stage of constructing an external sewer pipeline is backfilling the trench. I do not recommend treating this stage with disdain, since this is where beginners often make a large number of mistakes.

For backfilling, you can use the soil that was removed from the trench. First you need to make sure that there are no clods of earth, stones and other objects that could damage the PVC pipe.

I highly recommend using sand for backfilling (at least until the pipe inside the trench is hidden under its layer). In this case, the pipe is more reliably protected from soil shifts and, accordingly, depressurization.

In any case, backfilling should be done in layers, especially on the sides of the pipe, with intermediate compaction of the soil. This, again, is necessary to protect the engineering system from damage. You only need to compact the soil on the sides of the pipe, never on top. Plastic may not withstand such intense exposure.

A small mound should be poured on top, which is needed to compensate for the shrinkage of the soil after it gets wet.

By the way, if you plan to install treatment facilities with some kind of electrical equipment (for example, biological treatment stations) in a ditch before backfilling, I advise you to immediately lay a shielded electrical cable. So that you don’t have to worry about connecting electrical devices to the network later.

Construction of a wastewater treatment plant

In addition to pipelines, part of the external sewerage system is a local treatment facility. As a last resort, I suggest using a septic tank made of concrete rings, which copes well with the tasks and is quite simple to do.

Carrying out calculations

At my son’s dacha, I decided to build a three-chamber filter septic tank. Of course, you can say that its power is excessive for a structure where people are not expected to live permanently. But I decided to make a foundation for the future.

Moreover, this option has many advantages:

construction and operation of a septic tank is cheaper than a biological treatment plant;
you can build it yourself, without involving outside specialists (looking ahead, I can say that I only needed an excavator to dig a pit and a crane to install concrete rings).

Among the disadvantages, I can only highlight the possible appearance of an unpleasant odor (solved by installing a ventilation pipe) and the need to remove sludge from the bottom.

So, my septic tank will consist of three different chambers:

for primary sedimentation of sewage waste;
for purifying liquids from biological contaminants;
to remove purified water through the filter bottom of the chamber.

Some people replace the last compartment with drainage fields, but I decided to limit myself to this design so as not to carry out a large amount of excavation work.

If you are not going to install a washing machine at your dacha and invite a large number of people there to relax, you can limit yourself to one chamber, which will serve to remove solid inclusions.

Now about the size of the cameras. Let me give you some calculations. Let's say that 5 people are expected to live at the dacha (well, the calculation is to replenish the family). Each of them consumes about 200 liters of water within 24 hours, that is, the treatment plant must be able to receive 1000 liters of liquid per day.

According to regulatory documents and sanitary requirements, the local treatment plant must have such a volume as to accommodate triple the volume of dirty water, that is, about 3 thousand liters.

If the volume of a concrete ring is 0.6 cubic meters of water, then about 5 rings will be needed to build a septic tank. We divide it into three sections - it turns out that each chamber will have 2-3 rings. I'll do three to be sure.

Choosing an installation location

The second important point after calculating the required volume is the choice of location for installation. Moreover, this is done not at will, but in accordance with existing sanitary requirements.

The following requirements must be taken into account:

The minimum distance from a residential building to a septic tank should be 5 meters or more.
If you make a septic tank at a distance of more than 15 meters, you will have to pull a long pipe and make an inspection hole on it with a well for inspection. So I don’t recommend digging the pit too far.
The distance from the water intake source (well or well) to the treatment plant must be at least 30 meters.

By the way, one such moment. No matter how well and for a long time the septic tank works, sooner or later it will be necessary to clean it of bottom silt deposits using sewage disposal equipment. Therefore, you need to think about how this unit will approach your structure.

Earthworks

The next stage is excavation work again. This is not a narrow ditch; you will have to remove a fairly large amount of soil, so I immediately advise you to either hire workers or order an excavator.

The size of the pit should be slightly larger than the diameter of the concrete rings used. That is, if we take rings with a diameter of 2 meters, the pit should have a width of 2.5 meters. Then this space will be filled with clay to prevent sewage from seeping into the ground when the well is depressurized.

The depth of the well depends on the number of concrete rings used. Fold the height of the parts and go deep into the ground so that after installation and arrangement of the concrete floor are completed, only the inspection hatch remains visible from above to check the operation of the septic tank.

Installation of rings

To install reinforced concrete parts you will definitely need a crane. Otherwise, construction will take away your last remaining health. Despite the fact that the operation of special equipment requires additional costs, you will receive a durable, strong and sealed treatment facility that is well worth the money spent.

The installation itself is as simple as possible. You just need to lay the parts one on top of the other, making sure that the walls are oriented strictly vertically. The joints must be reinforced with cement mortar. If the soil at the dacha is subject to shifting and swelling, metal brackets can be used to strengthen the treatment plant.

To prevent movement of concrete rings, the bottom of the trench should be prepared before installing them. You need to make a cushion of crushed stone there, compacting it thoroughly.

The biggest hassle will be with arranging the bottom. In the first two chambers it must be completely sealed to prevent waste from seeping into the soil, and in the third well a filter pad made of crushed stone will need to be left.

I’ll tell you more about arranging a sealed bottom:

The bottom of the first two wells should be carefully compacted again, and then a reinforcing frame made of metal mesh or reinforcing bars should be made below. I always drill a little into the walls at the bottom to insert pieces of reinforcement into the concrete rings and ensure a good connection between the floor and the walls.
After this, prepare a concrete solution from sand, crushed stone and cement, which is used to fill the lower part of the well, leveling the surface with a trowel.
Work on the installation of septic tanks can continue only after the concrete solution has completely hardened. This usually takes from 2 to 3 weeks depending on the air temperature.

Construction stores sell sections of concrete rings already equipped with a concrete bottom. You can buy yourself two of these parts and not waste time and effort on concreting the bottom of the treatment plant. But a pillow at the bottom is still needed so that the entire structure does not move during operation.

Sealing

To prevent sewage from seeping into the soil, the inner walls of the well should be carefully sealed. For this, I recommend using a special mixture, for example, Aquabarrier.

To be on the safe side, I decided to seal the surface with bitumen resin-based coating waterproofing. Some go even further by installing plastic liners inside concrete tanks to keep water out.

At the same time as sealing, overflow pipes must be installed. This is done according to the following scheme:

The first pipe that connects the septic tank to a residential building is installed in the first chamber of the septic tank at a distance of about 50 cm from its upper part. Although this is purely subjective, because it all depends on the depth at which your pipes are laid.
The second pipe (between the first and second chambers) should also be installed at the top, but slightly lower than the first. The point is to pour out the settled water that accumulates at the top of the chamber through it.
The second and third chambers are connected in a similar way.

The photo shows an approximate layout of pipes in a septic tank.

Backfill

The last stage of construction of the treatment plant and the entire external sewage system is backfilling the septic tank. You can use the soil that you took out when preparing the pit, but I additionally bought fatty clay and filled the space around the wells with it. Thus, I created an additional barrier to prevent sewage from seeping into the soil.

Conclusion

External sewerage is perhaps a more important component of the wastewater disposal system at a summer cottage than the internal part of this utility network. To clearly see the installation process, you can watch the video in this article. And if you have any questions or your own advice, you can leave them in the comments to the material.

July 18, 2016

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