Septic tank device and principle of its operation. Determination of the size of the cleaner. Sump placement rules on the site. DIY installation technology. How to organize the drainage of liquid from a septic tank? The installation of a septic tank is the manufacture and installation of special tanks in which the effluents coming from the house are purified. The tanks form a local system for use in rural areas. In the article we will talk about the device of a septic tank and the process of installing it with our own hands.
Design features of a septic tank
A septic tank is a plant for treating sewage from private houses in places where there is no centralized sewage system. The simplest product consists of one or more reservoirs dug into the ground, in which the liquid gets rid of all inclusions. For the independent movement of water from one container to another, they are connected with adapters located at an angle. Two pipes are connected to the reservoirs for receiving effluents and removing the purified liquid. In the upper part, a hatch is provided through which the sediment can be removed from the container or the contents can be pumped out with a pump.
Liquid cleaning occurs due to the settling of solid particles and as a result of the decomposition of organic inclusions by bacteria. Depending on the design of the septic tank, 60 to 90 percent of the inclusions are removed from the drains. Water from the chambers is discharged outside and continues to be purified, seeping through sand and fine gravel. For this, a filtration well is built or a special drainage system is created on the site.
In the upper part of the septic tank there is a ventilation pipe through which the gas formed in the tank is removed. It appears as a result of natural effluent fermentation. If the vapors remain inside, the process is repeated and the contents of the container will come out through the hatch.
Chambers for septic tanks can be made independently or purchased ready-made, manufactured at the factory. The main thing is that they are sealed, safe, durable and efficiently perform their functions. A homemade cleaner is cheaper. A septic tank is often made from concrete rings, bricks, waste containers or special plastic cubes. It is allowed to dig a pit and finish the walls and bottom with concrete.
When choosing purchased products, pay attention to the price and manufacturer. It is important to purchase a quality tank, even if it is more expensive than other samples. Otherwise, it may leak and contaminate the area. There are autonomous septic tanks on sale with built-in special bacterial filters. They completely dissolve organic inclusions, so they do not need to be cleaned from solid elements. Such stations are popular among the owners of country houses due to the ease of maintenance, but they are very expensive.
Various materials are used to make a septic tank for the home. The advantages and disadvantages of each option are listed in the table:
| Material | Dignity | disadvantages | Application |
| Concrete rings | Short construction time, easy installation | It is impossible to ensure the complete tightness of the tank, installation is carried out using a crane | Areas with low groundwater levels |
| Monolithic concrete structure | High strength, tank tightness, long service life | Installation is very laborious, long construction period | With a high level of groundwater, if it is necessary to create a sealed cleaning tank |
| Plastic | Light weight, easy installation, long service life | Tanks are limited in volume | With a high level of groundwater and the need to create a sealed cleaning tank |
| Brick | The work can be done independently | It is difficult to ensure the tightness of the tank, installation is very laborious | In areas with low groundwater levels |
There are several types of septic tanks that differ in the degree of wastewater treatment:
- Single chamber … It is often called a cesspool. It is used if the groundwater is located close to the surface or there is a source of drinking water nearby. It is a sealed container into which drains from the house are drained through pipes. After filling the reservoir, the liquid is removed by a sewage truck.
- Two-chamber with mechanical cleaning … The first container is used to receive wastewater. In it, the heaviest elements sink to the bottom. Water with light inclusions is poured into the second compartment, in which the sedimentation of other elements continues. Thanks to microorganisms, the sediment decomposes into simple elements, which makes it easy to remove them outside. In a septic tank, sewage is purified by more than 50%. Then they enter a soil filter made of sand and gravel, which is also called a filtration field. It purifies water up to 95%. Bacteria present in the upper soil layers destroy organic inclusions remaining in the effluent. The purified liquid seeps into the ground. Two-chamber septic tanks need periodic cleaning from bottom sediments. If it is impossible to drain the effluents, a third tank is built, sealed, to collect the clarified liquid. Then it is used for economic purposes, for example, for watering.
- Two-chamber with biological treatment … This design contains special bacteria that decompose organic matter. Most of the inclusions dissolve in water. The liquid after the sump can be reused for economic purposes. Such septic tanks are very rarely cleaned, tk. microorganisms recycle almost all the dirt.
Septic tank installation technology
The installation of the device is carried out in several stages, including the development of the project, the assembly of the sump elements and the creation of a drain to drain the liquid. Before making a septic tank, be sure to measure the volume of water consumed in the house, the depth of the aquifer, find out the level of soil freezing, and also study the relief of the site. The sequence of work is shown below.
Choosing a location for a sump
The purifier is allowed to be built only on areas that meet the requirements of SNiP. When choosing a place to install a septic tank, consider the following:
- For the sump, choose a location away from wells and boreholes. On clay soils, ensure the distance between them is at least 30 m, on sandy soils - at least 50. If the chambers are sealed and the liquid from them is pumped out by a pump into the compost pit, this distance can be reduced to 5 m.
- From the house, he must be at a distance of at least 6 m.
- Place the septic tank in such a way that the drainage from the house flows in a straight line. If the condition cannot be met, install an inspection well at the turning point.
- It should be located below the level of the house, preferably along the natural slope of the terrain, in order to create a good outflow of water.
- It is recommended to locate the sump next to a place where it is possible to form filtration fields in order to reduce the cost of drain pipes.
- Provide a comfortable approach to the well as it must be cleaned once every 2-3 years. If you plan to use a sewer truck to remove waste, pave a road to the structure. Despite the fact that modern machines allow pumping from 50 m, it is recommended to install the tank no further than 5-10 m from the well.
- At least 1 m of dry soil should remain between the aquifer and the bottom of the septic tank. If the condition is not met, the drains will have to be removed using special equipment.
Sump volume calculation
In order for the septic tank to function correctly, determine its volume and the number of tanks. When performing calculations, consider the following points:
- The number of chambers depends on the number of drains. If they are collected up to 1 m3 per day, one well is enough, up to 10 m3 - 2, more than 10 m3 - 3.
- In most cases, two containers are enough for a private house, after which the liquid is removed into the ground.
- Select the size of the tank so that it accommodates three times the daily water consumption. This will allow the liquid to remain in the containers long enough for the dirt to settle to the bottom.
- In the calculations, use the value of 200 liters per day for 1 person. It includes drains from the kitchen, bathroom and toilet. Therefore, if there is one tenant in the house, use a septic tank with a volume of 600 liters. For a family of 5 members, purchase a tank of at least 3 m3… It is allowed to use a container of a larger volume, but problems with a smaller container will arise.
- The depth of wells for septic tanks depends on the level of groundwater, but in any case no more than 3 m, so that there are no problems with the sewer.
- Please note that the chamber cannot fill up completely, and there will be free space at the top.
For example, let's calculate the volume of a sump made of concrete rings, as well as the number of products for its manufacture. It is planned to build a concrete septic tank 3 m deep from rings 1 m in diameter and 1 m high. The drainage pipe from the house is located at a depth of 0.7 m.
The house is home to 5 people, so the capacity of the sump, according to SNiP, must be at least 3 m3.
Determine the useful height of the chamber: H = 3-0.7 = 2.3 m.
Calculate the working volume of the septic tank: V = S * H, where S is the area of the bottom of the ring, H is its useful height.
S = P * R2=3, 14*0, 52= 0.785 m2
V = S * H = 0.785 * 2.3 = 1.8 m3
For the construction of a septic tank with a capacity of 3 m3 you will need 2 containers of 1.8 m each3 (2 * 1.8 = 3.6 m3).
Use 3 rings for each tank, and 6 for the entire purifier. If you are planning a filter chamber (instead of a filter field), you will need another 3-ring well.
To increase the volume of the device, you can increase the diameter of the rings or deepen the hole.
Important! If the groundwater is located close to the surface, make the septic tank sealed, and remove the water from it with sewage trucks.
Construction of septic tank sedimentation chambers
Consider the process of installing a septic tank from reinforced concrete rings. It is the most popular material for sump construction. The structure can be made of standard products with a height of 1 m and a diameter of 700 to 2000 mm. Their number depends on the volume of wastewater. The rings are dug into the ground vertically, creating wells up to 3 m high.
The work is carried out in the following sequence:
- Choose a location for the septic tank and calculate the required number of rings.
- Dig two holes 20 cm deeper than the calculated sump height. Make their diameter larger than the diameter of the rings so that you can freely install the elements in the well. Leave an earthen layer of at least 0.5 m between the settling chambers. The soil layer acts as a buffer that will not allow liquids to freeze in winter.
- Pour a 20 cm layer of gravel and sand on the bottom, level the surface to the horizon and tamp it carefully.
- Concrete the site. The operation can be omitted if there are rings with a bottom.
- Inspect reinforced concrete products for cracks, holes and other defects. It is not allowed to use workpieces with any damage.
- Place the ring on the bottom using a tap. Seal the gaps between it and the bottom with aquacement, and then cover with waterproofing mastic.
- Place two products one on top of the other one at a time. To prevent them from moving, use samples with locks.
- Additionally, connect the products to each other with metal staples.
- Seal the gaps between them carefully.
- Make a hole in the upper ring of the settling chamber for the drainage pipe from the house. Just below, make two more openings in the walls of the tanks to install the adapter. It should be located at a slight angle so that the water moves by gravity.
- In the second container, make a hole to drain the cleaned liquid to the outside.
- Dig a trench from the house to the hole. Its depth is 0.3-0.7 m (according to SNiP), and its width is 0.4 m. Dig a trench with a slope towards the pit at the rate of 1.5-3 cm per meter. You should not deviate from the recommendations: a larger slope will lead to the fact that the water will flow faster than solid inclusions, and a smaller one will lead to blockages.
- Lay a 110 mm plastic pipe for outdoor use in the trench. It is not necessary to insulate it, the liquid flows out of the house warm enough not to freeze on the way to the septic tank. The pipe will be empty most of the time.
- Pass it through the hole to the inside of the camera.
- Connect both wells with crossover pipes.
- Insert the pipe for draining the purified liquid from the septic tank into the hole. Connect the drain adapter to it.
- Seal the entry points of products into the container and cover with waterproofing.
- Insulate the top ring with foam or special shell products. Insulate heat insulators with covers.
- Install special plates with holes on top of the cameras, they can be found on the construction market.
- Cover the large service opening with a hatch. In the small one, thread and fix the septic tank ventilation pipe. Place the lower part of the product above the maximum permissible liquid level in the container. For ventilation, use a cut with a diameter of 75-110 mm and a length of 2 m. The smaller size is not effective, and the larger one is impractical. Build a fungus over it.
- Fill the gaps between the septic tank and the soil with clay and compact it with water. After the procedure, leave the place of work for a few days. During this time, the soil will sag, and fill the gaps that appear with clay again.
Creating a filter field
At the last stage of purification, water is removed from the septic tank chambers and enters the filtering fields, where it finally gets rid of all inclusions.
To build it, do the following:
- On the site, dig a trench below the freezing level of the soil - usually 1.5 m. The width of the ditch is 50-100 cm. Its total length should not exceed 25 m.
- Trenches can be dug parallel to each other with a step of 1.5 m. If there is loam in the area, it is recommended to dig a pit in which to place the pipes with the required step.
- If there is a natural slope in the area, dig a hole along it. In other cases, ensure the bottom slope within 1 cm / m so that the water flows by gravity.
- Lay geotextile fabric in the hole and temporarily nail it with stakes to the ground.
- Place perforated corrugated pipes in the ditch and connect to the adapter coming out of the septic tank.
- Make sure they come down from the sump.
- Fill the pipes with expanded clay at the rate of 3 bags of loose mass per 1 m of the trench.
- Lift the geotextile and wrap expanded clay in it.
- Fill the trench with soil.
How to make a septic tank with your own hands - look at the video:
When constructing an autonomous sewerage system for a country mansion, the owner tries to find an inexpensive solution to the problem of waste disposal. We considered one of the options for solving the problem - creating a septic tank with our own hands from reinforced concrete rings. All work can be done independently, without the help of specialists. However, the purifier will function normally only if the construction technology described in our article is followed.
