The cesspool, as an element of sewerage in a suburban area, is gradually disappearing into oblivion. It has been replaced by septic tanks, which can be constructed from various building materials. These can be wells made of brick, blocks or stone.
In addition, you can build a septic tank from concrete rings, ready-made metal containers or plastic tanks. Owners of country houses most often give their preference to reinforced concrete rings.
What is a septic tank?
A septic tank is a reservoir or constructed well, the design of which allows it to perform the functions of a regular sump tank. The structure is divided into two or several parts by partitions.
The way it works is as follows: sewage flows into a septic tank and flows from one compartment to another. In this case, organic inclusions decompose into sludge and carbon dioxide. The first settles to the bottom, the second evaporates, and the clarified water penetrates into groundwater or is discharged outside the suburban area.
It is not difficult to calculate the volume of a septic tank yourself. To do this, you need only three indicators:
- The number of people who live permanently in the house. Please note, constantly.
- The amount of sewage waste from one person per day. This value is constant, it was derived experimentally and is equal to 200 l (0.2 m³).
- The amount of time it takes for organic inclusions to be completely processed is 3 days.
Calculation example
We increase this figure to an even number. So, the volume of the septic tank will be 2.5-3.0 m³.
How to choose the right rings?
Concrete rings for sewer wells come in different sizes. The height of all brands is the same - 90 cm. But the diameter is different: from 70 cm to 2 m. Accordingly, the volume of one ring will depend on its diameter. For example, a reinforced concrete ring with a diameter of 70 cm (0.7 m) has a volume of 0.35 m³. To build a septic tank with a volume of 2.5-3 m³, 7-8 rings are needed.
Rings with a diameter of 1.0 m have a volume of 0.7 m³. This means you will need 4 rings. This does not mean that this way you can win on the price of the septic tank. After all, the fewer rings you purchase, the larger they will be. This means that the price of each product will be higher.
When choosing, you need to take into account another point - the groundwater level. And the higher this indicator, the larger sizes you will have to purchase concrete rings. Their number decreases, which means the installation depth of the entire sewer system decreases.
Practice shows that most often consumers use rings with a diameter of 100, 120 or 150 cm.
Types of wells
The construction of an overflow septic tank made of concrete rings can be of two types:
- Multi-chamber (usually two-chamber).
Single chamber
The first option is not used today, as it is considered ineffective. Previously, a partition was erected inside the well. The bottom of the first part was filled with concrete mortar, the second was filled with filtering materials (sand and crushed stone).
At the same time, it was necessary to increase the size of the tank to the maximum, which led to the complication of installation work (especially excavation work), plus the efficiency of the entire installation was reduced due to the small filter surface area.
Double chamber
A two-chamber septic tank made of concrete rings is a more complex sewerage device, constructed from several wells. The scheme is as follows: the first of them is a collection tank into which sewage flows directly from the house. Here, during decomposition, the solid fractions sink to the bottom in the form of sludge, the lungs with clarified water pass into the second container through the overflow pipe.
Here the final decomposition of organic matter occurs, and most often the purified water penetrates into the groundwater layer through filter materials. Often, instead of a filtration well, filtration fields are installed. These are several trenches into which sand and crushed stone are poured, then perforated pipes are laid, covered with another layer of sand and crushed stone, and then with soil on top.
From the collection well, clarified water moves through pipes and through a natural filter, already purified, finally enters the groundwater.
Construction of a wastewater treatment plant
To build a septic tank from concrete rings, you will definitely need a crane. Even several people will be able to lift it manually with difficulty. And it is very difficult, almost impossible, to establish it exactly in place.
To facilitate installation work, experts recommend purchasing ready-made sewer well bottoms. Today these are produced by reinforced concrete factories. For the first container, a blind bottom in the form of a circle is used, for the second - with special through holes.
That is, there is no need for the first well to fill the bottom with concrete mortar using a reinforcing metal frame. In addition, installation time is reduced because there is no need to wait for the concrete solution to dry. And this usually takes up to 28 days.
Excavation
First of all, you need to dig a pit for the septic tank. Its dimensions are determined by the diameter of the concrete rings and their number, and therefore the volume of work carried out.
A pit is dug for two wells at once under a two-chamber septic tank. In this case, the distance from the walls of the pit to the rings should be within 50 cm. The bottom of the pit is leveled, covered with a sand layer of 10-15 cm, which is well compacted.
You can dig a pit with your own hands using shovels, removing the soil with a bucket. It's cheap, but it takes a long time. You can use the services of a small excavator. It's fast (two hours), but expensive. In the second case, you will still have to work with your own hands, leveling the bottom of the pit and its walls.
The bottom is installed on the prepared bottom of the pit using a crane. It is recommended to pre-treat it on both sides with waterproofing bitumen mastic.
Then the first ring is installed. It also needs to be waterproofed on the outside. To the first - the second and so on. After that, the joints between the rings are sealed from the inside of the well. Most often they are treated with liquid glass or cement mortar mixed with liquid glass.
Next, a concrete cover with a hole is installed, onto which a regular cast-iron hatch with a removable cover is subsequently mounted. You can use a homemade lid, but it is better if it is made of metal. This design must have a high degree of safety.
The second well is constructed according to the same scheme. The only difference is the creation of a filter layer under the perforated bottom of the tank. To do this, first a layer of sand is poured, then a layer of crushed stone. All other operations are carried out in the same way as in the first case.
Installation of sewer pipes
One of the main elements in the design of a two-chamber septic tank is the overflow pipe. It connects two wells to each other. Its location is determined by the pipe through which sewage flows into the septic tank from the house.
So, the overflow pipe should be located approximately 20-30 cm below the entrance of the main pipeline. In this case, it is installed with a slight slope towards the second tank, since the liquid will move through it by gravity.
This element is made from a plastic pipe. To install it in concrete rings, you need to make holes to match the diameter using a hammer drill. After installation, the joints must be sealed with cement mortar and liquid glass.
Final stage
All that remains is to fill the free space of the pit with soil and install a ventilation pipe on the lid of the septic tank. By the way, ventilation of a septic tank made of concrete rings is a mandatory condition. Through it, carbon dioxide comes out of the septic tank as a product of organic decomposition. But the ventilation device also plays a second role: oxygen enters through the pipe. It supports the vital activity of aerobic bacteria, which decompose organic matter.
And the final touch is decorating the area on which the septic tank is built from concrete rings.
It would be correct to design it according to the type of plantings that grow on the site. This way, it will be possible to hide both the ventilation pipe and the hatch.
It is very important to choose the right place to build a septic tank. The best option is not far from the fence where the road passes. The thing is that the collection well will have to be periodically cleaned of accumulated sludge. This is best done using a sewer truck. The distance from the house to the septic tank is at least 5 m, to a drinking well, borehole or any body of water – 50 m.
During construction, special attention must be paid to the joints of the rings. These are the most vulnerable places. They not only need to be sealed, but also well waterproofed. This is why it is recommended to use liquid glass. It would be nice if the internal surfaces of wells were treated with bitumen mastics. It's not cheap, but it will increase its service life.
Conclusion
So, a septic tank made of concrete rings does not belong to the category of “completed treatment facilities”. But at the end, if you correctly calculate its volume, choose a scheme and do the installation correctly, you can get fairly clean water. It will not pollute groundwater, and the sludge can be used as fertilizer.
The presence of a septic tank on the site is not only a matter of comfort, but also a sanitary and hygienic necessity. Such a device is required both in the house, subject to permanent residence, and in the summer cottage, where people come periodically. It is only important to choose the optimal design for specific conditions . A do-it-yourself septic tank made of concrete rings, the layout and location of which are correctly chosen, will have maximum efficiency.
Important for those who decide how to make a septic tank from concrete rings with their own hands: the design scheme may include from one to three containers, and with an increase in their number, efficiency increases, the need for the services of a sewer truck decreases, but the cost of the project also increases.
For clarity, we should consider in more detail the most complete version of the septic tank design made from rings using three containers.
Contaminated water is collected in the first, largest tank, where sedimentation and sedimentation of the largest fractions occurs, after which partially purified water undergoes a similar procedure in the second tank, which is structurally practically no different from the first (sometimes it is advisable to make it slightly smaller in volume).
The second tank deposits small inclusions, the water becomes relatively clean and flows into the third tank. Its distinctive feature is the presence of a filter backfill instead of a concrete bottom. Passing through the drainage layer, the water gets rid of remaining contaminants and goes into the ground.
The photo shows an example of how to install a septic tank from concrete rings with your own hands - a diagram of three containers
If a two-tank septic tank made of concrete rings is selected, the design may include two tanks with concrete bottoms or one with a concrete bottom and one with a filter layer.
Single-chamber models only collect wastewater and partially precipitate insoluble inclusions. Such modifications are cheap, but ineffective and are only suitable for periodically visited dachas. Removing contaminated water from a single-chamber septic tank can only be done using a sewer truck. Similar cleaning is required for both two-chamber and three-chamber designs, however, the required pumping frequency in these cases is much less.
For those who are looking for the simplest options, we advise you to pay attention to the fact that it can be done literally in one day.
We talk about the features of organizing sewerage in a bathhouse.
Design nuances and full equipment
In order to ensure that a self-made septic tank from well rings does not betray its presence with an unpleasant odor and does not have a harmful effect on the composition of the soil or water in nearby reservoirs, it is important not to neglect the nuances and equip the structure in accordance with the requirements.
So drain pipe (it is preferable to use plastic products) must have a slope of 2 cm per meter of length throughout and enter the concrete section no deeper than 20-25 cm from the top edge of the top ring. However, in practice, very often the pipe entry into the section occurs much lower when digging a trench and laying pipes deeper than the freezing level of the soil (approximately 1 m)
A special feature of the first section is the presence of a concrete bottom, which minimizes the likelihood of dirty runoff getting into the ground. The first section is arranged in a similar way when choosing a two-chamber septic tank, as well as the only tank of single-chamber models.
The design of a septic tank made of concrete rings for three or two containers provides for filling the bottom of the last of the reservoirs with materials capable of retaining large and medium-sized insoluble inclusions, if any remain, and draining the liquid into the ground. For this you can use sand, gravel or expanded clay, and The optimal solution would be layer-by-layer laying of materials with different fractions.
Preliminary calculations
The reason for the inefficiency of a structure or the inconvenience of its operation can be not only a violation of technology at the construction stage, but also an error in calculations when determining the required volume and the optimal location of the structure.
Based on the average volume of water consumption (one person per day approximately needs about 200 liters of water), it is customary to choose the following volumes of septic tanks made of reinforced concrete rings:
- for 2-3 people – 1.5 cubic meters. m (in this case there is no need to install a three-chamber structure; with proper organization of drainage and cleaning, two chambers will be sufficient),
- For 4 people, 2 cubic meter tanks are optimal. m,
- when installing one septic tank for 2-3 families (10-12 people) living in separate parts of the house, a volume of at least 5 cubic meters will be required.
The volume of the septic tank is set taking into account the fact that a full cycle of wastewater treatment requires an average of 3 days, so the tank must accommodate a three-day norm without the risk of overflow.
When choosing a location for the structure, the following requirements for the distance of the septic tank from certain objects should be observed:
- from natural bodies of water - at least 30 m,
- from the place of drinking water intake - at least 50 m,
- from fruit trees, vegetable beds - at least 3 meters,
- from the road at least 5 m (it is important to ensure the possibility of unhindered access for large vehicles, since at certain intervals the access of a sewage truck will be required to pump out wastewater, and during cleaning of the septic tank, disposal of the drainage layer material will be required).
Installation of the structure
Advantages
Having made a septic tank from concrete rings with your own hands, you can be sure that it will be durable and efficient. With proper use, it practically does not wear out, does not collapse and will last for decades. At the same time, you won’t have to spend a lot of money on maintenance.
When choosing a reliable and practical septic tank for a country house or country house, you should pay attention to concrete structures. The construction of a septic tank made of concrete rings meets almost all the requirements of modern users and has a lot of advantages. In particular, the treatment plant does not require power, which is especially important for areas where there are power outages.
Monolithic structures have a lot of advantages, for example, over plastic systems:
- Resistance to mechanical damage.
- Tightness.
Important! Monolithic structures have greater tightness, in contrast to a sump made of composite rings. But in any case, additional sealing of the seams will be required.
- Large mass. In contrast to plastic wells, concrete ones do not float up even during periods of soil swelling.
- Long service life.
- Easy to maintain.
You can install a monolithic concrete simple tank or a sump from rings with your own hands, but due to the heavy weight, it is better to take care of the availability of special lifting equipment.
Construction of a concrete septic tank, operating principle
Septic tanks made of concrete rings are best installed on draining soils that are not prone to frost heaving. Structurally, the body of a septic tank consists of two or more rings placed one on top of the other. The presence of protrusions for fixation and staples is a big plus, however, even with such fastening, the structure of the well can move, resulting in a leakage that will require repair.
Advice! Even after renovation, the concrete septic tank may be damaged, so it is recommended to install the structure on sandy, sandy loam or clay-peat soils.
In case of good drainage and/or low level of the ground aquifer, water can be drained from the sump into a drainage column - this is the most optimal solution. At high occurrence, purified flows are discharged to filtration fields.
The layout of the sump is quite simple: it consists of working chambers connected to each other by overflows and a filter or drainage well. The wastewater is purified in the chambers; the well is designed to discharge water into the ground, where the flows are further purified naturally.
The sewage treatment process is as follows:
- The first chamber receives all the drains. This is a sealed ring equipped with a bottom, where, under conditions of low air supply, the process of decomposition of biomass occurs through microorganisms. Organics are separated into slightly purified water and sediment that falls to the bottom.
- The clarified water flows into the second chamber, where the purification process continues, but under the influence of oxygen. To do this, the chamber must be equipped with a ventilation pipe. The remains of organic matter also settle to the bottom, but almost pure water enters the reservoir of the drainage well.
- From the drainage well, water is discharged into the ground, where the purification process is completed.
Bottom residues must be removed from the two chambers with your own hands or using a vacuum cleaner.
Possible layouts for septic tanks
To calculate the number of septic tank rings, it is necessary to take into account the total volume of wastewater for 3 days. The diameter of the elements can be 80-200 cm, but there are dimensions up to 250 cm. Height is from 0.5 to 1 m. Manufacturers offer a sufficient number of ready-made elements, both monolithic and with holes. When making calculations, it is necessary to take into account the actual volume of the column - it must be higher than the calculated one, since the drains never completely fill the elements, but only reach the level of the overflow pipes.
Installing a septic tank with your own hands requires not only preliminary calculations, but also the choice of option. This can be a well of one, two, three rings, or complemented by a system of drainage or storage wells.
Single chamber septic tank
The simplest design consists of only one ring equipped with a bottom. The chamber functions as a settling tank, where solid masses settle to the bottom, decomposing under the influence of anaerobic microorganisms. Light inclusions rise to the top, forming a film. The settled water exits through a pipe into the filtration fields.
The advantage of this system is its simplicity; installation does not require significant costs and everything can be done with your own hands. The ring is matched with a bottom, equipped only with a lid, plus filtration fields are equipped. The design is applicable for small volumes of wastewater (no more than 1m3/day). Such a septic tank made of concrete rings is not suitable for a permanent residence in a country house; it does not require sealing, but timely cleaning of bottom sediments is necessary.
Important! The treatment plant operates at 60-75% capacity, so the wastewater requires additional treatment.
The design flaw is the frequent clogging of the filtration fields pipeline due to solid insoluble particles that have not had time to settle. The installation of a treatment plant consisting of two elements minimizes the situation.
Two-chamber septic tank
This well system differs from the previous one by an additional chamber or partition in one concrete tank. The movement of flows is carried out through an overflow pipe, and the second chamber allows for more thorough filtering of organic matter.
The installation scheme includes the presence of two or more rings, with one (the first) equipped with a bottom, and the second may be without a bottom, but then an additional crushed stone filter is required. The height of the elements is calculated in accordance with the volume of wastewater required for processing. Advantages of a two-ring septic tank:
- High percentage of wastewater treatment;
- Low risk of pipeline blockage;
- Increasing the service life of treatment facilities and filtration fields.
Important! The arrangement of the structure requires equipping both chambers with hatches for technical work.
Disadvantages of a septic tank:
- A large amount of land work is required;
- It is necessary to arrange filtration fields;
- The design is indicated for processing wastewater with a volume of no more than 3 m3/day.
Three-chamber settling tank with deep cleaning and forced aeration system
This is already an almost perfect design, ideal for small houses for year-round use. Scheme of the treatment plant:
- The first chamber is a settling tank with anaerobic bacteria;
- The second chamber is a settling tank for processing residual masses, equipped with an aerobic aeration unit (compressor). The device supplies air to the chamber with a given power and frequency, due to which the functionality of microorganisms that process organic matter is launched;
- The third chamber is the pumping chamber. The wastewater is filtered and then discharged into filtration wells. This chamber can be supplemented with chlorination dispensers that operate automatically. Installation of dispensers is simple, everything is done by hand.
Important! A chlorination dispenser is a device that helps to completely disinfect waste streams before discharging them into the ground.
Regardless of the design features, rings for septic tanks are selected taking into account the volume of wastewater. Multi-chamber systems have better processing ability, but with a linear installation method they take up a lot of space on the site. The single-chamber system is quite compact, however, for thorough cleaning it requires the installation of filtration fields.
Advice! The first cleaning chamber is always equipped with a cast bottom. If there is no bottom at the ring, a concrete screed is installed or a slab is laid. Joints and seams are sealed inside and outside
Constructing a septic tank from concrete rings with your own hands is a matter that requires preliminary accurate calculations. Otherwise, you can end up with a structure that either cannot cope with the processing of wastewater due to its abundance, or will be half idle. Downtime negatively affects colonies of microorganisms, which die due to a lack of nutritious biomass.
The arrangement of elements is allowed freely. A standard septic tank contains a bottom ring, wall rings, and an upper ring equipped with a hatch hole and a fastening for the lid. Additionally, additional rings are used, which can be of standard or non-standard height and, as a rule, are needed when the soil shrinks.
Advice! Professionals believe that a large number of additional rings negatively affects the sealing of the structure and it is incorrect to carry out installation only using such elements. It’s easier to choose a bottom element of the desired height and wall (one, two) rings. The presence of fewer joints guarantees greater tightness of the tank.
General rules for installing reinforced concrete septic tanks
- The choice of rings with locks will facilitate the overall construction of the system: easier to install, higher degree of sealing.
- The optimal distance between columns is 0.5 m;
- The bottom rings are set perfectly evenly for the strength and durability of the entire column;
- The use of toxic compounds for sealing is contraindicated, as this will lead to the death of bacteria processing biomass;
- The upper ring of the septic tank must be insulated to minimize the threat of ice crust formation;
- The ring for the filtration well must have holes (perforated). The element is sold ready-made and only requires installation and addition of a filtration layer.
The do-it-yourself option for constructing a reinforced concrete septic tank is more practical in terms of financial and time costs. Due to the fact that all excavation work can easily be done with your own hands, there is no need to provide electricity (except for septic tanks with aerators and pumps), the treatment facility is considered the most suitable for small dachas and country houses.
Most private houses do not have a central sewerage system, which leads to significant difficulties with wastewater disposal. What to do in such a situation? In such cases, an autonomous sewage system is organized: a centralized collection of wastewater from all domestic and outbuildings on the site is carried out, which is disposed of in a cesspool.
Cesspools are the most common, but time does not stand still and they have been replaced by septic tanks. Septic tanks can be prefabricated plastic, as well as with deep cleaning stations.
Their disadvantage is their very high cost. An alternative option is to install a septic tank made of concrete rings.
Pros and cons of a concrete septic tank
Positive sides:
Reliability of the design. Reinforced concrete has high strength, durability and is able to withstand aggressive environments.
An overflow septic tank made of concrete rings is completely autonomous; it does not require additional elements for operation, such as electricity, pumps, drainage systems, containers for aeration and bacteria, etc.
Possibility of constructing septic tanks of various sizes and types. This is due to the wide variety of reinforced concrete rings: the diameter of the rings ranges from 0.5 to 2 meters. The height of the rings has two options - 0.6 and 0.9 meters.
You can build a small septic tank yourself, even without the involvement of heavy equipment. Installation does not require special skills or knowledge.
The septic tank is easy to operate - no human intervention is required.
A minimum set of materials and tools is required for construction.
Negative sides:
For the construction of large-capacity septic tanks, manipulators are required. This is due to the large mass of concrete rings and slabs.
At least two people are required for installation. Such septic tanks require periodic cleaning.
Septic tank layout and operation
Before starting work, it is necessary to decide on the location and schematic diagram of the septic tank made of concrete rings. It is worth remembering that the concrete septic tank must be located at least 5 meters from the house, at least 2 meters from outbuildings. If there are local sources of water supply: 30 or more meters from wells and boreholes.
The minimum distance between the septic tank and the roadway is 5 meters. The septic tank must be located directly on the site.
Septic tanks are single-chamber, double-chamber and three-chamber. An example of each type of septic tank made of concrete rings can be viewed in numerous photos of our selection at the end of this article.
The construction of more chambers is not advisable. The most popular are two-chamber septic tanks. Such septic tanks consist of two wells, between which there is a connecting pipe at the top.
The first well receives wastewater collected from all sources in the house. It is sealed (has a concrete bottom). As the first well is filled, the wastewater settles, and the wastewater decomposes into liquid, solid and gaseous parts.
The solid part is accumulated at the bottom, the liquid part is at the top, and the gaseous part is removed through a ventilation riser located at the very top of the septic tank (a hole is made in the well floor slab, the pipe is brought out 0.5-1.0 meters above the ground surface).
Having reached the mark of the connecting pipe, the liquid part is poured into the second well. The second well has a drained bottom (there is no concrete slab in the bottom - instead there is a crushed stone cushion).
As liquid waste flows in, it accumulates, settles and is absorbed into the soil. How to make a septic tank from concrete rings? It all starts with calculating the required volume.
Required volume
Depending on the volume of wastewater, the total volume of the septic tank is selected. For a standard family of 3-4 people, a septic tank of about 6-9 cubic meters is required. The calculation is based on the conditions of water consumption per day per person: 200 liters/day, as well as the minimum volume of the receiving waste pit for three days.
If there are 4 people, we get the total maximum volume of wastewater, taking into account a reserve of 200 liters - 1 cubic meter. This means that the receiving well must be at least 3 cubic meters.
The second well is usually made with the same volume. If there are more people, the number of rings in the septic tank and their diameter are increased, and additional chambers are erected.
The maximum volume of a three-chamber septic tank can reach 45 cubic meters of useful volume.
Preparation
After determining the location for the septic tank and calculating the required volume of wastewater, you can easily determine the required volume of the septic tank. The number of concrete rings, slabs for the bottom and covering depends on its volume (you can use ready-made rings with bottoms).
After purchasing and receiving all materials, you must:
Prepare the pit. It is worth digging a pit for all chambers at once (a large pit), with a margin of 0.5-1 meter for mounting rings on each side. The depth of the pit must correspond to the full height of the septic tank.
Level the bottom of the pit and cover it with a sand cushion 0.1-0.2 meters thick. Compact the pillow.
Digging of a pit should be carried out only by mechanized methods. When constructing septic tanks of small volumes (up to 4 cubic meters), you can do it manually.
Buy cement, sand, crushed stone, sewer pipes, bitumen mastic, well hatch. Make sure you have the necessary tools.
Septic tank installation
To build a septic tank, you need special equipment and at least 2 people. Installation is carried out from the bottom. The bottom is set to level. Further:
Installation of rings and coatings is carried out using manipulators. The rings are mounted on a cement-sand mortar, just like all covering slabs.
After installing the rings, perform coating waterproofing, protecting both the septic tank itself from moisture and preventing wastewater from getting through the walls of the septic tank into the ground.
The connecting pipe between the septic tank wells should be located at least 0.2 meters below the inlet pipe from the house to the receiving well. Make a drained bottom of crushed stone in the last well.
Seal the edges of the holes for pipes in the walls of the septic tank with cement mortar. After it has hardened, thoroughly coat this area with bitumen.
Maintain the slope of sewer pipes within 3-5%.
Conclusion
A concrete septic tank does not require a lot of time and money. It is a budget option for solving sewage problems.
Installation of small septic tanks made of concrete rings can be done with your own hands, without the use of special equipment.
Upon completion of the work, the septic tank must be equipped with ventilation pipes, the rings must be fastened together with longitudinal vertical corners or plates. It is most rational to place the septic tank at the lowest point of the site.
Photo of a septic tank made of concrete rings
Andrey Anatolyevich Ratnikov is an engineer who has been working since 1984 in companies related to waste disposal. Education and experience allowed him to develop his own septic tank design using concrete rings. The settling tank is made according to the classical design, but the essence of the invention is a filter well. When you read this article, it will become clear that everything ingenious is simple.
For an autonomous sewage system for a country house, it is not necessary to buy expensive industrial stations. A two-chamber septic tank made of reinforced concrete rings can handle wastewater treatment. It is important to arrange it correctly and calculate the performance. The design of the receiving chamber shown in the picture is classic.
An important role in the correct design of a septic tank is played by tees installed on the inlet and outlet pipes
You can see the sediment that has fallen, with particles floating on top that have not settled. To prevent the crust from going into the filter well, a tee is installed at the outlet, and another one at the inlet directs wastewater down.
The second function of tees is to provide cross ventilation of the septic tank. It is important to prevent odors from decaying organic matter from getting outside and into the house.
A treatment plant is allowed to be installed if the soil water is at a depth of 3 meters or more. When, when digging a pit, wet soil is discovered at a shallow depth, construction will have to be abandoned.
In the hole under the septic tank, level the bottom and fill it with sand to an approximate thickness of 15 cm. Pour water, so the sand will sink as much as possible. Not all purchased rings have a concrete bottom, so you will have to make it yourself and waterproof it. The upper ring is installed on the mortar or, better yet, special inserts are used to seal the seams.
Useful volume of septic tank The capacity of a septic tank required for full functioning is calculated using a well-known formula. It must ensure the intake of wastewater, the volume of which is equal to the three-day water consumption of one person.
According to the norm, one family member uses 200 liters in 24 hours, respectively, 600 liters in 72 hours. The last value is multiplied by the number of residents and the required volume of the receiving chamber is obtained.
In these calculations lies an error that is often not noticed, and then they are surprised that the septic tank does not cope with its task. Advice.
They calculate the total volume, losing sight of the fact that the container is filled with waste only to the lower level of the supply pipe. It is this volume that is useful, and it is taken into account in the calculations.
Important! The minimum depth of the septic tank from the top of the drain to the bottom is 1.2 m, the smallest diameter of the ring is 1 m. The greatest depth is 2.5 m.
| Table of sizes and volumes of well circles suitable for installing septic tanks: | Brand | Outer diameter, mm | Inner diameter, mm | Wall thickness | Height, mm | Weight, t |
| Volume, m3 | 11600 | 1000 | 80 | 290 | 0,2 | 0,10 |
| KS 10-3 | 11600 | 1000 | 80 | 590 | 0,4 | 0,16 |
| KS 10-6 | 11600 | 1000 | 80 | 890 | 0,6 | 0,23 |
| KS 10-9 | 1680 | 1500 | 90 | 290 | 0,32 | 0,14 |
| KS 15-3 | 1680 | 1500 | 90 | 590 | 0,67 | 0,26 |
| KS 15-6 | 1680 | 1500 | 90 | 890 | 0,96 | 0,40 |
| KS 15-9 | 2200 | 2000 | 100 | 590 | 0,98 | 0,39 |
| KS 20-6 | 2200 | 2000 | 100 | 890 | 1,47 | 0,59 |
KS 20-9
Rings with a diameter of 1.5 m or more are most suitable for constructing a septic tank, but they are inconvenient to work with - they are too heavy. The solution is to use smaller circles. To achieve the required volume, the structure is planted at a greater depth.
It is better to go the other way: connect 2 containers in series, the capacity of which will be equal to the required one. You will get a septic tank of two chambers, which works similarly to a single-chamber one.
Inlet and outlet tees
Holes are provided in the hatch cover directly above the tees. This allows you to clear them directly from the surface if they become clogged. The inlet tee plays an important role:
- drains are directed downward without destroying the crust;
- it does not clog the pipe when wastewater is discharged intermittently;
- easy cleaning from the outside without going into the well.
In the transition pipe to the filter container, sometimes a corner is installed instead of a tee. This is a mistake: when it is in the drains, the ventilation is blocked. Installing a simply open pipe is also wrong:
- the crust is destroyed;
- its pieces pass into the filter well;
- the pipe may become clogged.
The use of tees allows you to increase the useful volume of the septic tank. It is enough to place the overflow pipe just 5 centimeters below the inlet pipe. Water that is under the crust will enter the tee It is important to choose the correct dimensions of the tees for the septic tank. If they are not long enough, they do not provide crust retention; large sizes interfere with the formation of a proper settling zone, and the sediment at the bottom becomes agitated.
Filter well
Standards indicate that filtration tanks can be installed if the volume of wastewater does not exceed 1 m 3 per day. Another condition is sandy or sandy loam soil. This provision formally prohibited the construction of filter wells in areas with different soil. Practice refutes this norm: structures work normally even on loam. Clearly the rules took into account the small design drainage area.
The filter well can be built differently. Instead of placing the crushed stone filter inside the circle, where the area is limited by its size, it is increased.
- This is done in simple ways:
- the hole is not dug 25 cm larger than the diameter of the circle, but much wider;
- the bottom filter is placed not inside the well, but outside;
the bottom ring is made (bought) with holes in the walls.
This allows you to significantly increase the filtration area. With this design, the well is more of a distribution well - it transfers wastewater to a filter that is significantly larger than its size. This allows the height of the structure to be reduced. The waste flows out of a pipe that is located 10 cm or more above the filter. Its end is placed in the middle of the container. The jet falls not on crushed stone, but on a flat divider. It is made from a piece of any material heavier than water that is resistant to moisture.
Bottom filter
The correct choice of the bottom filter area is important. Only if it is of sufficient size will it ensure reliable functioning of the structure. You can use the table below, which shows how many liters of wastewater can be filtered by 1 m2 of soil, depending on its composition.
The inner surface area of a ring with a diameter of 1.5 m is 1.75 m2. If you install a bottom filter 2 m in circumference, this is already 3 m2 of filter, which will allow you to purify about 60 cubic meters of wastewater per day on clay, and 450 m3 on coarse sandy soil Proper ventilation device
To prevent a bad smell in the house and on the street, Ratnikov advises installing a pipe on the filter chamber, which serves for air flow. It flows through it into the well, then through the connecting pipeline into the septic tank. It exits through the top of the tee, which is never flooded with water. If there is no gap in the sump cover, the air continues to move through the pipes. It enters the supply line tee and goes into the house. The release of gases into the atmosphere occurs through a waste pipe, which is installed in the room and discharged through the ceiling and roof.
This is what cross-ventilation should ideally look like, when air enters the filtration well and is exhausted through the fan riser There are three options:
- If the system is gravity-fed, then the supply pipe is installed on the filter tank. The second one on a septic tank is unnecessary and harmful: the air will rush upward, where it meets no resistance.
- If the water supply system forces you to install a filter well on a hill, then when located close to the septic tank, the pump pressure pipe is laid in a thicker one. Air will flow through the latter. The scheme is the same: inflow into the filter tank, exhaust through the fan riser.
- When the second chamber is at a great distance, one inflow is installed on a container with a pump, if it is in a separate well, or on a septic tank, the second on a drainage tank. There is also a high-height exhaust, and the inflow is lower to create draft.
It is wrong to install a “fungus” on the hood, which becomes completely clogged with frost in winter. An open pipe always leaves a hole, albeit a small one.
If cross ventilation is not arranged, gases break out through all the cracks that are in the septic tank, filter well, and through the sewer system in the house. The problem is especially typical for dachas, where residents come occasionally. During your absence, the water in the siphons evaporates and naturally draws all the aromas from the septic tank into the house.
Answers on questions
Question No. 1. The standards of the STO Novostroy state that a properly constructed septic tank works for 20 years, during which time there is no need to change the filter material or remove soil. Is this true?
True, although the standards are cautious in assessing the operating time of a septic tank. In fact, it can last longer if you strike a balance between the amount of waste and organic matter coming in and the ability of bacteria to process it. Usually, improper operation leads to disruption of normal operation: the number of residents increases or large quantities of harmful substances that destroy microflora begin to be poured into the sewer system. Untimely removal of sediment also shortens the service life of the septic tank and disrupts cross-ventilation.
Question No. 2. If the slope of sewer pipes is made more than 2 mm per meter, why is this bad?
This threatens to clog the pipes. Water quickly runs through the pipeline, but the solid fractions do not have time to leave together and remain on the walls.
