Septic tank – autonomous sewerage for the home, installation, installation, maintenance

Individual sewerage in the house or in the country is the dream of many. Everyone is tired of using the outdoor toilet for a long time. Usually the limiting factor is the lack of the required amount. In this case, you can make a wastewater treatment system using a tank septic tank. It has a relatively low price, the service life is about 50 years. 

Design and operation

A septic tank looks like a large plastic cube with a ribbed surface and a neck (or two) sticking out above the surface. Inside, it is divided into three compartments, in which wastewater is treated.

The body of this septic tank is one-piece cast, it has no seams. There are seams only at the neckline. This seam is welded, almost monolithic – 96%.

Although the case is plastic, it is definitely not fragile – a decent wall thickness (10 mm) and additional even thicker ribs (17 mm) add strength. Interestingly, when installing a septic tank, the Tank does not require a plate and anchoring. At the same time, even with a high level of groundwater, this installation does not emerge, but this is subject to the installation requirements (more on them below).

Another design feature is the modular structure. That is, if you already have such an installation, and found that its volume is not enough for you, just install another section next to it, connect it to the already working one.

Principle of operation

A septic tank works in the same way as many other similar installations. The procedure for wastewater treatment is as follows:

• Water draining from the house enters the receiving compartment. It has the largest volume. While it is filling, the waste decomposes, roams. The process is carried out with the help of bacteria that are contained in the waste itself, and good conditions are simply created in the tank for their vital activity. During the cleaning process, solid sediments fall to the bottom, where they are gradually pressed. Lighter fat-containing dirt particles rise up, forming a film on the surface. The more or less pure water located in the middle part (purification at this stage is approximately 40%) enters the second chamber through the overflow hole.
• In the second compartment, the process continues. The result is a cleansing of another 15-20%.
• The third chamber has a biofilter at the top. In it there is an additional treatment of effluents up to 75%. Through the overflow hole, water is discharged from the septic tank for further purification (into the filter column, into the filtration fields – depending on the type of soil and groundwater level).
  

Not a bad exit

As you can see, there are no difficulties. With proper installation and operation, the Tank septic tank works flawlessly – it does not depend on electricity, so it is not afraid of frequent power outages in rural areas. Also, the installation tolerates an uneven usage schedule, which is typical for summer cottages. In this case, the flow of effluents on weekdays, as a rule, is minimal or absent, and reaches a maximum on weekends. Such a work schedule does not affect the cleaning result in any way.

The only thing that is necessary for dachas is conservation for the winter, if accommodation is not planned. To do this, it is necessary to pump out the sludge, fill all the containers with water by 2/3, insulate the top well (fill in leaves, tops, etc.). In this form, you can leave to winter.

Features of operation

Like any septic tank, the Tank reacts poorly to a large amount of active chemicals – a one-time supply of a large amount of water with bleach or a chlorine-containing drug kills bacteria. Accordingly, the quality of purification deteriorates, an odor may appear (it is absent during normal operation). The way out is to wait until the bacteria multiply or add them forcibly (bacteria for septic tanks are commercially available).

Another of the features that must be taken into account is not to flush waste into the sewer that does not decompose by bacteria. As a rule, these are wastes that appear during repairs. Not only can they clog the sewer, and you will have to clean it, but these particles significantly increase the amount of sludge, and you will have to clean the Tank septic tank more often.

Ways to organize post-treatment

At the outlet of the Tank septic tank, the drains are cleaned by 75-80%. As you know, without additional purification, they cannot be used. There are several options, and in many respects they depend on the type of soil (their ability to drain water) and the level of groundwater.

Normal absorbency and medium to low GWL

There is a regular way to drain water, developed by the same company – installing an infiltrator. An infiltrator is a container of a special shape, in the bottom of which there are numerous holes through which conditionally pure water falls down. This device is installed on a large crushed stone pillow – its minimum thickness is 40 cm (this is with the normal ability of soils to drain water, if the soils are clay or loam, the layer is increased). Remains of pollution remain on the rubble, and clean water goes into the ground.

The second option for post-treatment of wastewater after a septic tank is a filtration column. These are several concrete rings (2-4 pieces) of a meter diameter, dug into the ground near the wastewater treatment plant. First, a pit is dug under this column, a crushed stone pillow is poured on the bottom, then rings are installed, their joints are sealed, after which the gap between the walls of the well and the pit is filled up. The lower ring may have perforated walls. Through these holes or through the missing bottom, water is absorbed into the soil, where it is completely cleared.

Which is better – a column or an infiltrator

If we compare these two systems, then the installation of infiltrates is more environmentally friendly, and in practical terms it is more convenient. The fact is that after some time the rubble will silt with the remnants of pollution, the water will stop leaving. To restore the efficiency of the post-treatment, the crushed stone must be replaced. As is clear from the design, it is easier to do this if infiltrators are installed in pairs with the Tank septic tank. Their second plus is a large area from which water leaves. One infiltrator has an area of ​​contact with the ground – 21 frames, at the well – only a circle with a diameter of 1 meter, if the rings are ordinary, or about 4 squares, if the walls of the last ring are perforated.

Filtration field

The third option is the filter field device. This is when a fertile layer of earth is removed on a certain area, part of the soil is replaced with sand and gravel (30 cm minimum), plastic pipes are laid on top of this pillow, in the walls of which drainage holes are drilled. The laid pipes are covered with rubble, on top – soil.

Lawn grass is planted on this site or a flower garden is made on this site. You can not use this area for a garden or vegetable garden. The disadvantages of this method of post-treatment of wastewater are a large area, a large amount of sand and gravel, which will have to be changed after a while (it will also silt up).

The choice of the best septic tank for home and garden is described here. 

Periodic rise in groundwater levels under normal soils

Many houses stand in areas where groundwater rises periodically – during snowmelt or prolonged autumn rains. At the same time, the soil on the site normally drains water (sands, sandy loams, etc.), in a normal state, the water leaves quickly and only periodically its amount is so large that it can already stand half a meter below the ground level.

In this case, a storage well is placed between the septic tank and the post-treatment installation, in which almost purified water can remain for some time until the groundwater leaves. Then the water will be able to “dissolve” on its own. Methods for post-treatment of wastewater in this case are similar to those described above.

High groundwater level

In fact, the scheme is the same – with an intermediate well between the Tank septic tank and the post-treatment devices, but with a noticeable difference:

1. A non-return valve is installed on the pipe between the well and the septic tank. It is needed so that when the well overflows, the water does not go in the opposite direction – into the septic tank.
2. It is mandatory to use a pump for pumping wastewater in case of a threat of overflow of the system. You can output them to the same filtration plants.
3. There is only one way to treat wastewater – bulk filtration fields. Crushed stone is poured above ground level, forming a zone for wastewater treatment. Purified water gradually goes into the ground. These fields can be made with infiltrators or using perforated plastic sewer pipes.
   

What else can be said about this case – the filtration fields have a large area. The entire volume of water must somehow go away. If there is a drainage ditch nearby, the water can be directed there after post-treatment.

In general, the best solution for high groundwater levels is an aeration unit, such as Topas, for example.

Poorly conductive soils

The most difficult case. There is essentially only one option here – to make a filtering platform, and from it to remove the purified water into the gutter. Difficulty in arranging a filter ditch – a large amount of crushed stone is required, as well as a system for collecting purified water.

The choice of a septic tank for the house is described here.

Advantages and disadvantages

The main advantage of the Tank septic tank is its energy independence, which in a rural area or in a country house is undoubtedly a plus. The second pleasant moment is the relatively low prices for installations. When compared with the cost of concrete rings for a homemade septic tank, it turns out not so cheap, but given the difference in delivery, installation speed, the difference does not seem so significant. Another plus compared to septic tanks made of concrete rings is the tightness of the hull, as well as the fact that, with proper installation, the Tank is not afraid of heaving or slight ground movements.

Disadvantages are common to all septic tanks. This is a relatively low degree of wastewater treatment – about 75%, and the need for post-treatment, which often doubles the cost of the entire system.

Step-by-step installation of a septic tank Tank

Installation of a septic tank can not be called difficult. The main thing is to dig a pit for a septic tank and after-treatment devices, as well as trenches for pipes connecting all this and the house into one system.

The installation depth of the septic tank is determined by the depth of freezing. If it is not more than 1,50-1,70 cm, a septic tank is taken as standard. If the soil freezes by 2 meters or more, an additional neck is used, respectively, the installation depth increases.

The pit is dug to such a depth that only a cover remains above the ground + 3-5 cm for sand bedding to level the bottom. The dimensions of the pit should be 25 cm or more larger than the dimensions of the septic tank.

Installation of a septic tank Tank with photo

Next, step by step:

Preparation and

Digging a pit. This can be done manually or using technology. We level the bottom, pour sand in a layer of 3-5 cm, compact it, level it.

• We drop the body. It is convenient to do this on the ropes, passing them between the ribs.
• We check whether the septic tank has become even (building level laid on the neck covers).

To the inlet pipe, which is located on the upper surface of the body, we connect the sewer pipe from the house. We also lay the pipe to the post-treatment installations or to the intermediate well (depending on the chosen scheme). Pipes are better to use polyethylene for outdoor use (red color). They withstand negative temperatures, normally tolerate loads.

Backfilling

So that there are no problems with the septic tank, and after the winter it does not appear on the surface, it must be properly “anchored”. To do this, water is poured into the installed housing. It bursts the walls to the working level. The soil is gradually poured, rammed.

• When the level in the tank rises by about 20 cm, we begin to fill the gap between the walls of the pit and the body of the septic tank. For backfilling, we use a sand-cement mixture: for 1 part of cement we take 5 parts of sand. It is necessary to fall asleep around the perimeter, manually, without the use of equipment. Having fallen asleep 20 cm, the layer is compacted with a manual rammer, making sure not to damage the body. During backfilling, the water level in the septic tank should be 20-30 cm above the sand layer. This ensures that the walls are in the correct position when working.
  

• Having filled up the walls to the upper part of the body, pour about 15 more cm of the mixture, level it and compact it.
• Lay a layer of insulation. The best option is extruded polystyrene foam (EPS), you can also use isofol. The use of polystyrene is undesirable – it can flatten from soil loads and stop working. It is absolutely impossible to use mineral wool – it is hygroscopic and after a while it will simply crumble into dust. The insulation layer depends on the region and the type of material used. For example, EPPS for Central Russia requires 5 cm, for the northern regions – 10 cm.
  

• On top of the insulation we fall asleep “native” soil. The height of the backfill is flush with the ground level.

This is all. Septic tank installed. There are a few more points regarding the creation of a sewer system. It makes sense to insulate the sewer pipe that comes from the house. In regions with not very cold winters, it is enough to lay the EPS on top (it should cover the pipe and protrude 7-10 cm along the edges). It can simply be covered with soil.

In the northern regions, only a heater on the pipe may not be enough. In addition to this, the pipes are heated using heating cables for water and sewer pipes. To make the heating efficiency higher, it is laid not outside, but inside the pipe. Only the shell must be resistant to aggressive media.

Installation of the infiltrator

One of the components of an individual sewage system using a septic tank is an infiltrator. This is a device for the post-treatment of wastewater leaving the septic tank. It is a plastic container made in the form of a trapezoid, in the walls and bottom of which there are many slot-type holes.

Relatively small in size – 1800 * 800 * 400 mm, it holds up to 400 liters of liquid. It is laid on a crushed stone pillow with a height of 40 cm or more. A layer of crushed stone of this height is necessary on soils with a normal ability to drain water, on poorly drained soils it can be 70 cm or more.

What to do

The number of required infiltrators depends on the magnitude of the volley discharge, as well as on the characteristics of the soil. With the same capacity of the installation, on sandy, well-draining soils, fewer additional cleaning elements are required than on soils with medium or poor drainage capacity.

The procedure for installing an infiltrator for final wastewater treatment is as follows:

• We are digging a pit, which is 500 mm larger than the infiltrator.
• The bottom and walls are lined with geotextiles. It is needed so that the gravel does not mix with the soil.
• We pour and level the layer of rubble.
  

  

• We lay the body of the infiltrator.
• We connect it to the outlet of the septic tank.
• We install the ventilation pipe.
  

  

• We fill it with sand so that it fills the body from above by 15 cm.
• We lay a layer of insulation (it can be the same as on the body of the septic tank Tank).
• We fall asleep with soil.

When installing the infiltrator, it is not necessary to use a mixture of sand and cement, since the body lies on a crushed stone cushion, which successfully compensates for all movements.