How to make a sealed septic tank?

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How to make a sealed septic tank?
How to make a sealed septic tank?

Types and features of a sealed septic tank. Location selection, preparatory work and installation technology.

A sealed septic tank is a closed chamber with a waterproof bottom for collecting and recycling sewage. How to install such a tank on the site or make it yourself is our topic today.

Types of sealed septic tanks

Two-chamber hermetic septic tank
Two-chamber hermetic septic tank

Typically, sealed sewer septic tanks are built in areas with soils that have a low carrying capacity or a high level of the aquifer. Such structures require special care when operated with strict observance of sanitary requirements.

By the number of sections, one-chamber, two-chamber and three-chamber septic tanks are distinguished. Let's consider brief characteristics of each of them:

  1. Single chamber design … Such a septic tank is called accumulative, serves only to collect wastewater, takes up a minimum of space on the site and is suitable for a household that consumes up to 1 m3 water going into the sewage system with waste. In fact, it is a technical well made of a waterproof monolithic material. As it fills, a single-chamber septic tank requires pumping out sewage with sewage equipment. It is desirable that the volume of the waste tank corresponds to the capacity of a tank truck that takes waste for disposal.
  2. Two-chamber design … Such a septic tank has two compartments, serves for collecting, settling and partial purification of effluents, reaching 60%. The tank is designed for 10-12 m3 liquids. The compartments are interconnected by two overflow pipes located in the partition. One of them is at the bottom of the wall, the other is higher. After settling, liquid fractions of effluents overflow from the first compartment to the second through the bottom pipe. The upper pipe serves to limit the maximum level of waste in the collection tank and prevent it from overfilling. A special inspection well is provided for pumping out wastewater in a two-chamber septic tank.
  3. Three-chamber design … Such a septic tank consists of three sections and is designed for the processing of sewage if their daily volume exceeds 10 m3… The first section, which serves as an accumulator, receives all liquid waste from the house. In terms of volume, it occupies 50% of the entire structure. The second section, occupying 30% of its volume, serves as a filter in which anaerobic wastewater treatment is carried out. Purified water is removed from the third section, which can be used on the farm, for example, for irrigation. All chambers of the septic tank are equipped with overflow pipes.

Features of sealed septic tanks

Hermetic septic tank in the country
Hermetic septic tank in the country

Any sealed septic tanks for summer cottages are capable of operating in rather difficult geological conditions. The main problem they are called upon to solve is the operation of the sewer tank in conditions of high soil moisture, which creates problems for such structures both in summer and in winter.

Intensive movement of water flows in summer can complicate the installation of a septic tank, provoke its flooding or flooding, and have an aggressive effect on the tank body. In winter, when the soil swells, frozen water, expanding and squeezing the reservoir, can cause its destruction.

Not every septic tank material is capable of withstanding such loads. Therefore, sewage tanks for soil saturated with groundwater are made of metal, durable plastic or monolithic reinforced concrete.

Due to the fact that the main condition for a septic tank on watered land is its tightness, three design options are possible:

  • Storage tank with periodic pumping of wastewater;
  • Anaerobic septic tank;
  • Aerobic SBO.

The sealed storage tank can be made from steel, plastic tanks or concrete. Plastic container is lightweight and can float during floods. Therefore, it is installed in a pit, fastened with cables to a concrete slab, which serves as a kind of anchor. When creating such a slab at the bottom of the excavation, hydrophobic substances are added to the liquid concrete, and after it has hardened, the site is covered with a coating waterproofing.

Device concrete septic tank requires a lot of work, but the design is reliable and durable. To create it, you will need to install complex formwork and knit metal reinforcing cages.

Anaerobic septic tanks

non-volatile - the liquid in them moves by gravity. But with an increased GWL in such reservoirs, it is necessary to install an evacuation pump, since drainage does not work under such soil conditions, so it makes no sense to do it.

Aerobic station

is more complicated. It is equipped with a compressor that requires a power supply to operate. In addition, to pump out the treated water, you need to regularly start up the drain pump. This leads to additional costs, but the degree of liquid purification approaches 98%.

Important! It is almost impossible to make a sealed septic tank from concrete rings, car tires or bricks with an increased GWL. Therefore, it is recommended to avoid the use of the listed materials under such conditions.

Choosing a location for a sealed septic tank

Place for a septic tank
Place for a septic tank

When choosing a location for a sealed septic tank, you must be guided by the following:

  1. The installation of a septic tank cannot be made closer than 5 m from a residential building.
  2. The distance between outbuildings and the structure should not be less than 1 m.
  3. The distance from the fence of the neighbors' site to the sewer tank must be more than 1 m.
  4. It is forbidden to install a septic tank closer than 50 m from a well or a well with drinking water.
  5. The volume of the sewer tank should be at least three times the daily intake of liquid waste into it.

These requirements are established by sanitary standards and are mandatory. In addition to taking them into account, for the correct installation of a septic tank, it is necessary to calculate its dimensions.

Preparatory work

Digging a pit for a septic tank
Digging a pit for a septic tank

Before making a sealed septic tank, you need to perform a number of preparatory work. You should start by digging a pit. The excavation for the reservoir and communications can be dug with shovels or using an excavator. The first option is more suitable for a single-chamber small septic tank, where the use of technology is not justified by the price of such services.

Before starting excavation work, it is necessary to determine and mark with pegs the location of the sewer pipes for draining wastewater, and then dig trenches for them, taking into account a slight slope of 2% for the natural movement of liquid waste along the highways.

The pit can have a round or rectangular shape in plan. Cylindrical recesses are usually made for each chamber of a sealed septic tank, and trenches are dug between them. For a rectangular two- or three-chamber structure, a common pit can be prepared, since the compartments of such a septic tank are created using partitions.

At the last stage of preparation, it is necessary to make the bottom of the septic tank. Concrete, mortar or brick are suitable as the main materials for a sealed structure. Before pouring the solution, a 10-15 cm layer of rubble must be poured onto the bottom of the pit and compacted. The resulting surface should be covered with a reinforcing steel mesh. The diameter of its rods is taken as 8-12 mm. The layer of cement mortar, which you want to cover the reinforcement, should be 120-150 mm. After it dries, the bottom of the pit must be covered with waterproofing - roofing material, for example.

Another option for the bottom of such a septic tank is a brick structure. After installing the reinforcing mesh on the crushed stone pillow, the bottom of the pit must be filled with a layer of 50 mm cement mortar. After that, one or two layers of bricks should be laid on top of it and a leveling cement screed should be made with the addition of liquid glass to the mixture.

Installation options for a sealed septic tank

Installation of a septic tank made of in-situ concrete
Installation of a septic tank made of in-situ concrete

When mounting a tank in wet ground, you need to choose the right tank material. Any brick or septic tank made of rings will not be airtight under these conditions. Therefore, it is better to forget about them for this case. Such structures with joints are highly hygroscopic and, when exposed to water on their walls from both sides, often do not withstand such a load. In addition, it is extremely difficult to make a septic tank from prefabricated elements in a soil saturated with water.

The ideal option would be a factory made fiberglass tank specially designed for the collection and treatment of liquid waste.

It has absolutely sealed chambers, overflow pipes and excellently withstands compressive loads. It is enough to install a finished septic tank in a pit, and after connecting to the sewer pipes, such a structure can be immediately operated. His work is very effective. The system collects and settles the effluent, and then completely cleans it. The result of its work will be 98% pure liquid in the third chamber, which can only be pumped out or dumped into the reservoir.

When using aerobic organisms in such a reservoir, it is possible to reduce the amount of silt in the compartments and later fertilize the soil of the garden or vegetable garden with them. This will give significant savings on the services of the sewers.

If the purchase of a sealed plastic septic tank for sewage causes financial difficulties, the treatment plant can be made with your own hands from monolithic concrete. The container will be without joints, which will increase its reliability.

The work must be done in this order:

  1. Dig a pit according to the planned dimensions of the septic tank.
  2. Install the formwork that forms the walls and partitions of the future structure. In the formwork of the partitions, it is necessary to leave holes for the overflow pipes.
  3. After securing the formwork with stops and spacers, reinforcing frames must be installed along the entire height of the wooden structure, which will strengthen the concrete after setting.
  4. The concrete mix for pouring must contain a water-repellent additive. In the process of filling the formwork with concrete, the working mixture must be compacted using a deep construction vibrator. This will help remove the pores in the walls of the septic tank after the concrete has finished curing. It will take 7-10 days for the mixture to dry in the formwork. After the end of this period, the formwork can be removed.
  5. After making the walls of the septic tank, you can proceed to the device of its bottom. To do this, the base of the tank should be tamped down, then covered with sand and a similar procedure should be followed.
  6. A steel mesh should be laid on a sand cushion and filled with cement mortar with a layer thickness of 10-15 cm. After the bottom is completely dry, the inner surface of the concrete septic tank must be covered with a coating waterproofing.
  7. The last stage of work is the overlapping device. Its installation should begin with the installation of metal corners on the upper part of the walls of the septic tank. They will give rigidity to the entire structure.
  8. On top of the corners, you need to lay the boards across each chamber. If the width of the section is more than one and a half meters, the flooring should be reinforced from below with support pillars so that future pouring does not push it with its weight.
  9. On the boardwalk, you need to lay a reinforcing mesh, install the formwork on top and pour concrete into it. In this case, do not forget about the holes for the ventilation pipes. Places for them must be left. Such pipes should be 100 mm in diameter and protrude 60 cm above the tank overlap.

After completing the above stages of work and connecting the sewer main, the sealed concrete septic tank will be ready for use.

How to make a sealed concrete septic tank - watch the video:

Installation of a sealed treatment plant on wet ground requires compliance with many recommendations. But in general, an inexpensive storage tank is suitable for summer cottage conditions, and for a house you will have to install a full-fledged water treatment plant.