Do-it-yourself septic tank made of concrete rings: dimensions, how to do it yourself

A comfortable existence is impossible without sewerage. In a private house or country house, this is usually a cesspool or septic tank. The second option is more environmentally friendly and safe – a septic tank. It decomposes waste into insoluble sediments, which fall to the bottom, forming silt, and fairly clean water, which is usually discharged into the ground for further purification. Probably the most popular version of this installation is a septic tank made of concrete rings. The technology of its construction is simple, you can build it yourself, the cost is relatively low. This explains its popularity. 

The device and the principle of operation

A septic tank made of concrete rings is best placed on well-draining soils that are not prone to frost heaving. The body of the septic tank consists of several rings placed on top of each other. Even if they have ledges for better fixation, even if they are stapled together, frost heaving will move them. The result is leakage and costly repairs. And not the fact that after the repair it will not move again. Therefore, it is recommended to make a septic tank from concrete rings on sandy or sandy loamy soils.

If the soils drain water well, the groundwater level is low, it makes sense to remove water from the septic tank to the drainage column. Such a device is the most optimal. With a high level of groundwater, treated effluents are diverted to draining fields. Their device requires large areas and no less solid volume of earthworks, but sometimes only such a system works.

The scheme of the septic tank is shown in the photo above. It consists of two working chambers interconnected by an overflow. This is where the cleaning process takes place. The third column is a drainage well (instead of it there may be a filtration field), through the holes in the lower part of which purified water enters the soil. This is briefly about the construction of a septic tank made of concrete rings. Now about the process itself.

Drains enter the first chamber. It is hermetic, with the most limited air flow. In conditions of lack of oxygen, the main process of decomposition takes place in it. Organic substances are processed by microorganisms and bacteria. Organics breaks down into more or less pure water and insoluble substances that precipitate and accumulate at the bottom of the chamber.

Through the overflow pipe, water with less pollution enters the second chamber. The cleaning process continues in it, but here it occurs with the obligatory participation of oxygen. Therefore, the second chamber is equipped with a ventilation pipe. Here, the remains of organic matter decompose and settle to the bottom. Almost pure water is discharged into the drainage column and goes into the ground, where their final purification takes place.

Sizes of septic tanks and their number

In order for the drains to be effectively cleaned, they must be in the septic tank for at least 3 days. Based on this, the dimensions of the chambers are determined.

How to determine the volume of a septic tank

According to the standard, the minimum volume of a septic tank chamber is three times the daily water consumption. 200-250 liters are considered per person. In total, if you have 4 people in your family, the minimum volume is 3 cubes. This is how much the storage tanks, that is, the first two chambers, should contain. The third – the filter column – in no way belongs to the storage column, therefore it is not taken into account.

It was about the regulations that are in force in Russia. In Europe, the minimum volume of a septic tank is 6 cubic meters. And many believe that such sizes are more “correct”. Effluent in large volumes stays in storage tanks longer, which means they are cleaned better. When using the native standard, in the event of the arrival of guests, it is easy to “pour” the norm. As a result, untreated effluents will end up in the filtration column, which will pollute it and the entire surrounding area. Elimination of consequences is an expensive and complicated procedure.

Even if you decide to adhere to Russian standards, if you have a bathroom, a washing machine and a dishwasher, you need to increase the volume at least by the size of the salvo discharge of all these devices (bathroom – 300 liters, washing machine and dishwasher 50 and 20 liters, all together – we will consider 400 liters or 0,4 cubic meters).

In accordance with the calculated volume, the sizes of the rings and their number are selected. The diameter of a concrete ring can be from 80 to 200 cm, sometimes there are rings with a diameter of 250 cm. Height – from 50 cm to 1 m. The table below shows the dimensions of standard reinforced concrete rings, their marking, weight and volume. In the “dimensions” column, the outer diameter, inner diameter, height are indicated through a fraction. All measurements are in millimeters.

When calculating, keep in mind that the actual volume of the column must be higher than the calculated one – the drains never completely fill, but rise only to the level of the installed overflow pipes. It is up to the level of these pipes that the calculated amount of drains should be placed.

Number of columns

There can be three storage chambers in a septic tank (except for the filter column). Sometimes such a device is more practical – if it is required, for example, to install six or more rings in each of the columns. The depth of the pit in this situation is large. It is more convenient / more profitable to make three columns of four rings.

There may be a reverse option – a small volume of a septic tank is required. This happens at the dachas of periodic visits with a small number of summer residents serving it. In this case, the column can be assembled alone, dividing the rings inside with a sealed partition. and making an overflow hole at the required level.

How to

The most common construction principle is linear. All columns line up on the same line. Accumulative can be located nearby, and filtering – at some distance from them and preferably away, so that the flowing waters do not saturate the soil and do not freeze, enhancing the phenomena of frost heaving.

General rules for storage columns

It is better to take rings for a septic tank with locks. They are easier to install, they are less likely to shift during frost heaving, and the degree of sealing is higher. Before installation, it is desirable to treat them with coating waterproofing. Good results are obtained with bituminous mastic and deep penetration impregnation based on cement (Penetron type). With this treatment, nothing will seep out of the septic tank, and groundwater will not get inside.

The remaining rules for constructing a septic tank from concrete rings are as follows:

• The optimal distance between the storage columns is 0,5 m. This gap, filled with soil, will act as a buffer during soil movements.
• A layer of crushed stone about 20 cm thick is poured and rammed at the bottom of the pit. It is rammed to a high density, better – using a powerful rammer. The surface of the bedding must be strictly horizontal and even, without drops. The plane is checked using a building level with a length of at least 1,5 meters (preferably 2 meters).
• On compacted rubble:
  • Put rings with the bottom. They must be set exactly so that the walls go strictly vertically. Then the column will stand firmly.
    

  • A concrete monolithic slab with a thickness of at least 30 cm is poured under the septic tank, larger than the device by 20 cm in all directions. The plate must be strictly horizontal and as even as possible. After the concrete has matured (28 days), the first ring is installed on the slab, its joint with the base is carefully sealed. To do this, a roller of concrete mortar with improved waterproofing characteristics (such as Aquacement) is laid out under the ring. The squeezed out remains of concrete are used for sealing the joints between the rings.
• All subsequent ones are installed on the first ring. The joint of each is carefully sealed. You can lay out a layer of the same Aquacement before installing the ring on the side. After installing all the rings, the joints are once again coated with a waterproofing solution from the inside and outside. It is impossible to use toxic compounds inside – the bacteria responsible for the decomposition of bio-inclusions will die and the septic tank will not work.
  

• For a stronger fixation of the rings, they are connected using metal brackets (installed outside. The “entrance” places of the brackets are concreted, coated with waterproofing.
• It is desirable to insulate the upper part of the septic tank (above the freezing depth). For this, a polystyrene “shell” is used or expanded polystyrene cut into strips is glued. The drains, of course, are warm, but in severe frosts there is a risk of an ice crust forming, which reduces the purification efficiency. Therefore, insulation is desirable.
  

• For reasons of economy, necks are made in the upper part of the septic tank columns. Sewer pipes in the area are usually buried below the freezing depth of the soil. This is 1,5-1,7 meters in Central Russia. And they have to go with a bias. Let the slope be small, but since the length of the route is large (no closer than 8 meters from the house), quite a decent amount runs up. In total, it turns out that the sewer enters the septic tank at about 2 meters and the entire part of the column, which is above, is empty. So they reduce it with the help of a head, which can be done:
  • From brick. Plaster outside and inside, treat both sides with liquid waterproofing. The option is good because you set the height and dimensions of the hatch yourself, but you will either have to buy a reinforced concrete floor slab for rings with a hole for the manhole, or pour the floor slab yourself.
    

  • From special concrete covers with hatches. At the same enterprises that produce concrete rings for sewer septic tanks, they also produce ceilings with hatches. They are mounted on the top ring of the column and fit standard metal or rubber caps.
    

  • From monolithic reinforced concrete. The option requires minimal costs, but requires a long period of time and certain skills in creating reinforced concrete structures. It is necessary to assemble the formwork, tie the reinforcing frame, pour concrete. The neck will be ready for operation in 28 days.
• The overflow pipe between the chambers of the septic tank is made with a diameter of 110-120 mm. It can be made of asbestos or plastic. Its entrance is carefully sealed.
• The inlet pipe that comes from the house and the overflow pipes between the chambers are equipped with tees. This directs the effluent downward, preventing crust erosion (it is needed for better effluent processing). Sometimes tees are equipped with pipes going down.
  

• The location of the overflow pipes is determined by the level of the inlet pipe (from the house). The overflow on the opposite wall should be 5 cm below this level. Between the second chamber of the sump and the filtration well, the overflow can be done at the same level, or lowered by the same 5 cm.

Features of the construction of a filtration well

When constructing a filtration column, a pit is dug to soils that drain water well. A layer of crushed stone 20-25 cm thick is poured at the bottom, a layer of sand 30-40 cm thick is placed on top of it. Rings without a bottom are installed on this bedding. In some cases, a perforated ring is placed – holes of at least 30-50 mm in diameter (there are, by the way, factory ones).

When installing a perforated ring, it is also desirable to replace the soil around with crushed stone. This is necessary for the water to drain better. Otherwise, the device of the filtration well made of concrete rings is the same.

How to bury rings for a septic tank

The most common way is to dig a common pit, install rings with a crane, lay overflow pipes, seal all joints / cracks, seal, insulate, then fill and compact the soil. Everything is not bad, except that the amount of excavated land is very large. To make everything quick, it is easier to use the services of an excavator. Manually, with your own hands, it takes a long time, and if you hire a brigade of “diggers”, it will turn out to be both long and expensive. Typically, the cost of a team of diggers is comparable to the cost of calling special equipment. It’s just that the equipment works for several hours, and the team – for several days. But this may not be the case in all regions.

There is a second way to bury a concrete ring – methodically remove the soil inside the ring and under the wall. Under its own weight, the ring falls down. But only rings without a bottom are buried in this way. The bottom will have to be poured later and it will be exclusively inside the ring, which greatly reduces the reliability of the septic tank. In addition, with this option, it is impossible to insulate the septic tank, except to dig it to the depth of freezing. You will also have to dig trenches for laying overflow pipes. A rather problematic method for septic tanks, but you can use it.

Economical septic tank made of concrete rings

The linear arrangement of the columns of the septic tank requires a solid area, you have to take out a large amount of land. Also, each of the columns must be equipped with a neck, which further increases the cost of the structure. There is an interesting option with the installation of all columns in a triangle. there is already a saving of space and a reduction in the volume of land work.

The second point of savings is that the revision entrance can be made one for three rings. Only all overflows must be installed in the zone of its accessibility. There are no other features.