Septic tank technology in clay soil. Septic tank on clay: design features Septic tank for clay soil choice

When installing septic tanks, it is necessary to take into account the following nuances:

Groundwater level and soil type.

The location of the place for installing a septic tank relative to the house, well, fence.

Is there a drainage system from this site (ditches, drainage).

The depth at which the pipe runs out of the building.

The degree of slope of the site.

In absolutely ideal conditions, the installation of a septic tank can be carried out at a depth of at least 75 cm from the surface layer of the earth, in order to protect the container from freezing in winter. So, for example, in some regions of Russia, the depth of freezing of the earth in winter according to SNiP is 140 cm, but in reality, 75 cm will be more than enough for a septic tank.

Consider the option of installing a septic tank with clay soil and an extremely high level of groundwater. In this case, the installation of a septic tank must be done so that the filtration field (drainage) made after the septic tank is slightly higher than the water level, otherwise the runoff will not dissolve very well in the soil, which means that such a septic tank installation will not be considered correct. The installation of the septic tank should be done shallowly and lightly sprinkled with earth on top, so that a hill is obtained. It can also be insulated with foam, insulation, for example, K-flex-ST or its analogues. When installing a septic tank into the water, it is required to anchor it with concrete beams. The septic tank itself will almost always be full of water, and therefore, to prevent it from rising, it does not require too much mass to strengthen the septic tank in the soil. If the installation of a septic tank is carried out in very difficult conditions, for example, in a swamp, then the installation of the septic tank must be carried out using a concrete slab (the septic tank in this case is attached to the slab using metal strips), with further lowering of this structure using a manipulator into the pit.

When installing septic tank in clay it is very difficult to make the necessary scattering field, because the crushed stone drainage will begin to collect all the water from the site from rain, and therefore, the drainage will be in the liquid and it will be bad to leave. This means that the drain can be made into a ditch, or a special well can be made at the very end of the dispersion field in order to install a drainage pump in it, with further pumping of water into the sewer.

A septic tank consists of one or more separate chambers. Fluid flows through them. The configuration of the septic tank, and the depth of its placement, depend, first of all, on the performance of this facility and its overall dimensions. It is required to lay the septic tank on such soil that is not subject to swelling and other deformations during severe freezing or thawing.

If the soil freezes significantly in cold winter, then the container is laid in a sufficiently deep pit, moreover, its bottom must be in a non-freezing layer of soil, or on a special base in the form of a concrete pillow. The simplest septic tanks, like the "Tank" or "Triton" systems, as a rule, are deepened so that the thickness of the soil from the soil surface to the septic tank body is at least half a meter.

For the normal stable operation of any treatment plant of this type, it is extremely important that flood waters in no case stagnate, and the height of groundwater must be more than one meter. If your site is poorly drained, then the septic tank is laid shallow and covered with soil in such a way that a small hill about 50-70 cm high is formed. Free access must be left to all technological openings. It is worth considering that the angle at which the liquid flows through the chambers of this septic tank must be at least 50.

In addition, for good operation of the septic tank in clay or other dense soil (heavy loam) that does not pass water well, it is necessary to install two-stage filter trenches. The first trench is equipped with a sand and gravel pad 30 cm thick. A perforated filter pipe is laid into it at a depth of about 0.5-1 m., In another trench - at a depth of 1.5-2 m.

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The choice of a septic tank for clay soil and its installation are complex tasks that require compliance with a number of rules. Incorrect installation of such structures on loam can cause deformation of the septic tank and disrupt its operation.

It is difficult to install a septic tank on clay, because. the characteristics of this soil do not predispose to the rapid disposal and purification of wastewater. Clay does not absorb water well. Effluent stays in the tank. Sandy soil can absorb up to 90 liters of water per day, while loam - only 25 liters. Pure clay has lower water absorption rates. In addition, clay soils are characterized by high density and high weight. When arranging an autonomous sewage system, these features must be taken into account.

Why are septic tanks installed in clay deformed, and how to avoid this?

Most often, when arranging septic tanks, large-volume plastic containers are used. They are a good option for many types of soils, but they are not quite suitable for clay. Having a high density and weight, clay often deforms containers even from dense plastic during seasonal temperature fluctuations. In some cases, deformation of even metal containers is possible. In addition, septic tanks in clay soil are often deformed due to ground movements. This happens especially often if the groundwater is too close to the surface.

When planning the installation of a septic tank in clay soil, it is necessary to take into account the danger of possible deformation of the container. To prevent the occurrence of such a problem, it is desirable to use rigid materials for arranging the structure, including concrete rings, slabs, etc.

Plastic containers can also be used if desired. But to protect them from soil movements, it is imperative to make a special construction of concrete or a strong wooden crate. This will avoid damage to the integrity of the tank due to ground pressure. If the groundwater level is low, metal fittings or corners can be used to make the crate.

What septic tanks can be used in clay?

When arranging a septic tank on clay soil, it should be borne in mind that it is almost impossible to create high-quality filtration fields, so classical multi-level systems should be abandoned. There are several options for autonomous sewers that can be used effectively.

Storage tanks

The simplest and cheapest option for a septic tank, suitable for arrangement in clay soil, is a storage system. In conditions of clay soil and to save money on pumping water in the future, you can use a complex storage system consisting of several tanks connected to each other. Such cleaning systems can be created on the basis of:

• concrete rings;
• wells lined with bricks;
• large metal barrels;
• plastic containers, etc.

Such a septic tank for clay soil is an analogue of a cesspool and requires the systematic pumping of accumulated effluents with a sewer machine.

With soil treatment

Septic tanks, consisting of several storage tanks and an artificially created filtration field, can reduce the cost of pumping wastewater. In this case, some of the already settled effluents will enter the filtration field and go into the soil. The design in this situation will be simple. Several containers are connected in series with each other so that heavily polluted drains remain in the first of them, and the already settled water penetrates into the next container.

It does not have to be only 2 containers. Some homeowners connect 3-4 containers at once. This allows you to ensure that almost clean water enters the last cavities of the septic tank. The difficult moments of arranging such a system are the preparation of the site and the installation of the filtration field system.

Due to the presence of clay in the place where the filtration field will be located, it is required to dig a pit 1 m deeper than the bottom of the pit intended for installing the system. At the bottom of the pit, gravel or gravel is poured, as well as a layer of sand. Perforated pipes are laid inside such a pillow so that purified water from the last tank can be discharged to the filtration field. It should be borne in mind that there must be at least 50 cm of crushed stone and sand on top of the pipes.

In the process of shrinkage, the filtration field can become heavily clogged with clay and cease to perform its function. To delay such an unfavorable outcome, the finished filtration field should be covered with geotextiles. Clay can be poured over this material. This will avoid inflating the clay and clogging the cavities between the rubble with it.

For biological treatment

Closed septic tanks with biological treatment are very popular with owners of sites with clay soils. Such systems are autonomous sewer stations. They give a high degree of purification, so in the future the resulting water can be used for technical needs and for irrigation of the site.

Such autonomous sewers are multi-chamber products, where effluents immediately undergo fractional division and settle. The clarified effluents are additionally treated with special bacteria that process all organic compounds present.

Design features of a septic tank for clay

The physical properties of clay soils change slightly during the period of freezing and thawing. This often becomes the reason for the gradual pushing of the septic tank to the surface. Especially this problem often occurs when installing septic tanks, which were made of lightweight materials, including plastic and metal.

To prevent the occurrence of this effect, fixing the structure in the pit is required. For additional fixation, metal reinforcement and concrete mortar are often used. If the surface of the container is equipped with special holes, metal cables can be used to fix it at the bottom of the pit.

In addition, a thick bed of gravel and sand is recommended to prevent tank displacement. It is also allowed to manufacture a concrete slab, which will serve as the base. When filling it, you can make "ears". With their help, you can later more securely attach the septic tank to the base.

When performing earthworks when arranging an autonomous sewer, all safety measures must be observed, since clay can quickly collapse. It is best to dig a septic tank hole at least 1.5 m wider and longer than required. This will avoid surprises due to the collapse of the clay.

Features of installation on clay soil

When planning the installation of a septic tank on clay soils, it is necessary to comply with the sanitary requirements for the location of autonomous treatment facilities. The distance to the house and other capital buildings should be at least 20 m.

In addition, if a septic tank for clay soil has a filtration well and will purify water not only due to the operation of a sewage machine, it must be taken into account that the distance to a well or other source of water must be at least 50 m. This will prevent pollution by drinking water.

It is best to start installation when dry weather sets in for a long time. This will ensure the reduction of groundwater. When digging a pit, all precautions should be observed. The height of the pit must be at least 70 cm more than the height of the selected septic tank. A 10 cm layer of sand is laid at the bottom of the pit. After that, 30 cm of a layer of gravel is poured. On top of this, laying geotextiles is recommended.

After that, a connected reinforcing mesh is laid at the bottom of the pit, which is necessary for pouring the concrete substrate. If necessary, a wooden or metal crate is formed to protect the septic tank from being squeezed. After the bottom of the pit is prepared, you can proceed to the installation of the septic tank design. Be sure to fix the container with cables or metal rods. After that, you need to install all communication pipes, fill in the cavities around the septic tank and compact the soil.

The life of a modern person is filled with a variety of items that provide comfort and convenience. These include water supplied to the house, bathroom fixtures, and a toilet.

But such comfort systems, if they are not part of the overall system, which is possible in urban apartment buildings, need an individual wastewater and waste treatment system. Previously, people managed with an ordinary sewage pit, from which the flowing masses were absorbed into the soil, and when they accumulated exorbitantly, the ditches were cleaned with the help of special machines, or the pit was simply transferred to another place.

The disadvantage of this method of getting rid of sewage was the saturation of the soil and even water wells with pathologically dangerous microorganisms, which, as a result, became the cause of many diseases of humans and animals. As well as contamination of the land and bringing it into a state of unsuitability for agricultural use.

In order to protect the earth and humans from dangerous microorganisms, wastewater treatment systems were invented, and our company has been installing such systems for many years.

Today, the cheapest and easiest to install treatment option is septic tank, which is a complex single-section or multi-section design that provides partial purification of wastewater and its absorption into the soil or partial drainage. At the same time, the septic tank provides for ground filtration, in which the liquid passes through the soil layers, for this you need good drainage properties of the soil and a considerable field of drainage action.

Installing a septic tank on clay soil

Many people, in order to save money, use septic tanks and install them in clay, but such a solution is simply a waste of money and labor. Whatever myths go around septic systems, they are designed for sand or other types of soil capable of quickly absorbing liquid.

They are not suitable for a clay environment due to poor drainage of this type of soil layer - our specialists always explain this to the owners of clay plots, but they do not always listen and drive themselves into unnecessary waste. A recent case with a septic tank in clay has become a prime example of the irrelevance of such cleaning equipment for clay terrain.

We were approached by people due to a malfunction of the septic tank, when opening the pit, our specialists found a completely deformed container, completely unsuitable for cleaning anything.

Why are septic tanks installed in clay deformed?

By itself, the septic tank is not able to absorb large amounts of water, since it is designed for low-volume flow, in addition, it requires good drainage, that is, so that part of the treated water goes into the soil.

Liquid absorption is not typical for clay, and this leads to the accumulation of liquid around the septic tank or complicates the work for the drain pipe, which, in turn, simply cannot accommodate the amount of liquid designed to pass through the soil layer. Thus, pressure is exerted on the body of the cleaning device and it is deformed.

Due to the impassability of the soil, the water simply crushes the septic device. An additional destructive factor is such a clay feature as frost swelling, in which in winter the clay soil itself begins to put pressure on the septic tank and either pushes it out or deforms it if it is securely fixed.

Making a surface outflow of water is also not relevant, since the septic tank does not completely clean the liquid masses and draining such water into a ditch or reservoir threatens the spread of harmful bacteria, which means it promises environmental problems.

What to do if the septic tank is deformed?

Many people who experience a failure of a septic tank installed in clay blame the manufacturers of the septic system or the people who installed it. At the same time, would-be owners again order and install a similar treatment system, and after a short time again get the same result.

The only solution to this problem, as practice shows, is to replace the wastewater treatment system with an option that is suitable specifically for clay. The most practical solution for non-absorbent soil is considered to be a biological treatment plant, which is relevant for any type of soil.

It was this decision that our specialists made, having taken the above-mentioned deformed septic tank out of the ground, and it turned out to be the only correct one.

The thing is that the work of a septic tank is based on absorbable soil and an extensive filtration field, for which clay cannot act as a field of action, since it does not let water through. The sewer pipe of the equipment is not able to do the work for the soil, that is, to pass such a large amount of water, in this case, either the septic tank itself is deformed if it is made of fragile materials such as polypropylene, or the pipe breaks if the body of the cleaning device is made of concrete mixes .

Features of the biological treatment plant

The main advantage of the biological station is that it is suitable for any type of soil. It differs from a septic tank and a high level of purification, which is about 98%. In fact, any impurities, thanks to special microorganisms, on which the operation of the device is based, are converted by this installation into two types of useful raw materials: clean industrial water and compost.

Since the water obtained after filtering with a biological station is completely safe, it can be drained into a ditch, used for watering plants or for other technical needs, while not a single environmental indicator will be violated. The resulting solid raw material can be safely used to fertilize the soil and plants. The following features of the biological station can also be called important:

• Compactness, since such a cleaning device does not take up much space;
• Tightness and strong structure, in which the ingress of sewage into the soil or water bodies is completely excluded;
• Duration of operation, which can reach more than 50 years;
• The ability to use the raw materials obtained after cleaning for technical purposes.

Principles of installing a septic tank

A septic tank is the simplest form of treatment plant, and its installation requires compliance with certain rules. Due to the fact that such a cleaning system is not particularly safe, since it is not characterized by complete purification of liquids, such a device should be located no closer than twenty meters from a residential building.

An additional condition for installation is the location of a well or a well with drinking water, the distance between it and the septic installation should be no more than 50 meters.

For clay soils, which have low drainage rates, but are considered an excellent medium for the spread of intestinal bacteria, this distance can be figuratively increased to 80 meters.

The principle of operation of the septic tank is based on the settling of waste, so its capacity should be designed for a three-day rate of liquid waste so that they have time to settle. In clay soil, there is no possibility for repeated ground filtration, and when settling, the liquid drains poorly due to the strength of the clay, which makes the relevance of a septic tank in clay a common myth.

Principles for installing a biological treatment plant

The biological treatment plant is smaller in size, since it does not involve a long settling process. Unlike a septic tank, in which waste liquids must stand idle for three days, such a device allows you to clean the raw materials in a time not exceeding a few hours.

At the same time, there is simply no need for additional ground filtration, because the processing and purification of wastewater is carried out due to the impact of biological organisms (bacteria) on them, for which waste becomes a food product. As a result of such biological processing, the water obtained as a result of processing can be discharged into any reservoir, ditch, ravine or used for watering plants, since it does not contain hazardous substances at all.

The body of the biological station is always airtight and made of durable materials, so for installation it is possible not to move the treatment station a long distance from the living quarters, and since the waste after such purification is safe, you should not be afraid of the installation being close to a well or water pipes.

Another advantage of this treatment equipment is that it does not require insulation, since it works from the mains and provides for preheating.

What to choose?

Some owners of clay plots still prefer to use a cheaper septic tank, instead of a biological treatment system, and are looking for ways to properly install it.

Many not entirely conscientious experts offer additional fixing of the septic tank in order to prevent it from being pushed out during frost. It is often recommended to install a septic device near the surface in order to provide at least partial drainage and filtering by the topsoil. At the same time, for the possibility of functioning, the device is insulated with the help of additional materials.

All these methods are good only theoretically, in practice, any of them will soon lead to the destruction of the septic tank and malfunctions in the autonomous sewer system.

If the site is endowed with clay soil, the only way to provide high-quality wastewater treatment is a biological treatment plant, without which it is simply impossible to make an autonomous sewer system located on clay soils safe.

It so happened that our comfort and additional amenities often become the cause of environmental pollution, especially in places with clay soil. In order not to harm the environment, each owner of private sewer systems is simply obliged to take responsibility for wastewater treatment.

In this case, saving in the form of a septic tank will be the wrong decision, threatening unforeseen consequences, therefore, preference should still be given to a biological treatment plant.

The design for the clay type of soil must be chosen especially carefully, because it must be a high-quality sewage system, which, moreover, will clean sewage from sewage and bring out just clean water. Some models will even allow you to reuse the water that has already gone through one cycle, although, of course, not for drinking purposes.

The fact is that sandy soils are able to absorb up to ninety liters of liquid per day. If it is sandy loam, then this figure is reduced to fifty liters, loam - half as much. And if you have dense clay soil, then it will absorb no more than five liters of water per day. Therefore, the sewer system is built according to other canons.

As a rule, clay in the soil is located only the top two to three meters. This is noticeable, for example, if you equip a well: below you can see sandy loam or generally clean sand, which perfectly absorbs water. The well works even better this way than if the soil were homogeneous due to the pressure of the water column. Thus, first study in detail the type of soil on your hacienda. Ask old-timers, neighbors, those who recently built something, or simply order geologists who will conduct professional exploration. Then you can save on arrangement septic tank in clay instead of buying a ready-made cleaning station.

The design of the septic tank can be anything - plastic, brick, reinforced concrete or concrete. You can choose the material without regard to the clay soil, based on the budget and personal preferences. If you have good black soil on your site, then you can water the crop with purified water from a septic tank. To do this, you will need to put a sealed tank instead of a filter well, and connect a drainage pump to it. Then the supply of purified liquid will be provided to the irrigation system.

Septic tank in clay: reviews, installation, where to drain water. Such a septic tank is suitable for giving, but if you constantly live in a house outside the city, then it is not advisable to buy such a septic tank. Another disadvantage is a rather low percentage of cleaning, so there may be an unpleasant odor. But it can be neutralized with an aeration system.

However, very often even the most dense soil shows good absorbent properties. You can use this to increase the area that absorbs water with filter fields. To do this, cover the entire area with rubble, lay drains with two-centimeter holes on them. The length depends on the number of residents. For each person there should be a ten-meter pipe. From above, it is also necessary to fill ten centimeters of gravel, and put black soil on top. Plants that need abundant watering can be planted on it. This is a convenient solution, because the degree of cleaning does not affect anything, and it will not smell either. If you lay the pipes to a forty-centimeter or greater depth, then in winter they will not freeze, and you can continue to use the septic tank. However, in soils that do not let water through at all, it is impossible to equip such a system.

However, even in this case, it is possible to drain the liquid directly onto the site or a specially dug ditch. In this case, it is better to take a non-volatile sewer system with aeration. The principle of operation is about the same. The first reservoir must be air-filled so that the aerobic bacteria can live and work. In the next compartment, the sludge settles and is transferred back to the first tank by the compressor. And in the third chamber, the water is finally purified and pumped into a ditch or onto the ground, from where it evaporates.

Installation of local sewage treatment systems (septic tanks) is often complicated by mining and geological conditions (soil composition) and high groundwater levels.

These reasons create problems with the discharge of treated effluents into the ground. The most difficult thing is to mount a septic tank on clay, which has a minimum liquid filtration coefficient.

The main problem at this stage is related to the fact that almost all clays (90%) belong to soils prone to frost heaving. It is because of this reason that it is possible to extrude the installation to the surface, so it is necessary to resort to additional fastening of the local treatment plant during installation. Most often, the so-called bandage of steel strips or cables is used for this, which encircles the septic tank and is attached to the concrete base in the pit.

Considering that on clay soils, drainage systems (filtration fields) in many cases work only in the upper layers of the soil, it is necessary to resort to a shallow septic tank.

In this case, it is necessary to provide measures for the insulation of the structure:

Insulation of a septic tank with glass wool

• In the simplest case, they resort to filling an additional layer of soil above the relief (forming a hillock above the installation site of the septic tank).
• It is more efficient to insulate the treatment plant with special heat-insulating materials, the choice of which is quite wide. The most affordable (in terms of cost) method is filling the container with expanded clay. More effective is the use of expanded polystyrene (preferably extruded) or polyurethane foam. In addition, active protection systems against the effects of negative temperatures are increasingly being used. To do this, use a heating electric cable, the thermal power of which will reliably protect the septic tank from freezing even in harsh climatic conditions.

Removal of treated wastewater

The main problem for those who decide to arrange an autonomous sewage system and mount a septic tank in clay soil is the difficulty of removing treated wastewater. Such soil has a minimum filtering capacity, which creates a number of sometimes intractable problems.

There are several main ways to remove treated effluents from a septic tank in such conditions.

It is used if the soil on the site absolutely does not accept water. In this case, the entire volume of treated wastewater enters a sealed container or well, from which it is then pumped out using sewage equipment or drainage pumps.

The disadvantages of this method include the need for a large capacity device, otherwise pumping will have to be done very often. But if there is no other way out, it is necessary to use this particular technology.

Increasing the drainage area

There are several varieties of this technology, but they all boil down to the need to increase the filtration area in order to ensure the removal of the required volume of treated effluents even with the minimum drainage capacity of the soil.

• The device of a number of successive drainage wells, while it is necessary to use rings of the largest possible diameter.

In practice, systems of two or three overflow drainage wells are used, which can fully meet the needs of a family of 3-4 people.

To increase the filtering capacity of wells, they resort to drilling additional drainage wells. This method allows in some cases to reach the filtering horizons of the soil, which will help to significantly increase the productivity of the structure. Drilled wells must be protected with casing pipes, and a simple mesh filter should be installed at their mouth, which will prevent silting of additional drainage.

• Install a septic tank in clay with your own hands It is also possible with the device of filtering fields of a large area. This method is used at high GWL (groundwater level).

The most productive is the drainage system using corrugated plastic pipes and geotextiles. Pipes of this type are characterized by increased strength, they are able to provide an effective removal of treated effluents. And geotextiles prevent silting of the system.

To increase the efficiency of the filtration field, two-level drainage is often used. In this case, a number of lines (drains) are laid close to the surface, and the main part is deepened as far as the groundwater level allows.

The filter line is laid in pre-prepared trenches, which are covered with a geotextile sheet. Drainage pipes are laid on top of granite rubble (it is not recommended to use another one due to the tendency to erosion) with a thickness of at least 20 cm. From above, they are also covered with a layer of rubble, which can significantly increase the volume of discharged effluents. The entire resulting system is covered with geotextile, which will ensure the durability of the line.

To ensure the filtration of wastewater in conditions of clay soil, it is necessary to lay significant filtration fields in terms of area.

Of course, the installation of septic tanks in clay involves a significant increase in the amount of work performed during installation. But it is quite possible to ensure the efficient operation of local wastewater treatment plants even under such conditions.