The device of the filtering drain pit, the advantages and disadvantages, the calculation of the volume and location on the site, the materials used for the work and the stage-by-stage construction technology.
A cesspool without a bottom is the simplest domestic sewage system that does not need a weekly pumping out of household waste. Despite this, its operation requires compliance with all sanitary and hygienic requirements. How to build a technical well of this type is our topic today.
The device of a cesspool without a bottom
Structurally, a drain pit without a bottom is a well up to 3 meters deep, made of concrete rings, clay bricks or truck tires. The bottom of such a structure is a soil or filter consisting of a layer-by-layer backfill with sand and gravel.
The walls of the filter well have many drainage holes, through which the liquid fraction of the effluent goes into the outer soil, where the soil is subjected to additional treatment. The bottom filter has a similar function. Insoluble fractions of sewage remain in the drain pit and are pumped out by sewage equipment a couple of times a year.
Such a cesspool is suitable for disposal of wastewater in the country during the warm season or in a village house in which 1-2 people constantly live.
With a larger number of people, the effectiveness of the filter pit will be insufficient due to the increase in the amount of water consumed for household needs and to be discharged into the autonomous sewage system. If such a cesspool overflows, runoff can cause soil contamination, this will violate the environmental safety of the entire site. A way out of this situation can be the construction of a septic tank, consisting of 2-3 chambers.
Pros and cons of a filter cesspool
Structurally, the filtering cesspool differs from a sealed structure by the possibility of drainage through the bottom filter and walls. This functionality has its positive and negative sides.
The advantages of a sewer well without a bottom include the following:
- Low cost of construction due to the absence of the need for formwork and concreting during its construction.
- Compactness. The volume of the filter tank usually does not exceed 2 m3, therefore, the autonomous sewage system, created on its basis, takes up little space on the site.
- Ability to naturally clean up liquid waste. This is the most significant plus of this design. Due to the fact that part of the effluent is filtered through the walls and bottom of the tank and goes deep into the soil, the services of sewers are required less often. The economic effect is evident here.
Disadvantages of a cesspool without a bottom:
- Remote location. According to SNiP, filtering drain pits are prescribed to be equipped much further from water sources or housing than similar closed-type structures. The reason for this is the risk of soil contamination in the event of impurities entering it. The usual distance from the object for such wells is increased to 20 m.
- Environmental hazard. If untreated runoff enters the soil aquifer, it can quickly spread over many kilometers, poisoning the land and thereby reducing its fertility. Therefore, in this case, it is not even necessary to talk about a high yield from a vegetable garden or orchard.
- Limitation in the volume of the well. For a large family, a small filter cesspool will not be enough. It is pointless to make more of its volume, since this will absolutely not affect the hygroscopicity of the bottom of the tank.After all, filtration is a long-term process that can end with stagnation of drains with an increase in the permitted size of such a cesspool.
Estimated norms for the construction of a cesspool
Competent calculation of the volume of the filtering drain pit is an indispensable condition for its correct operation. First of all, you need to know that such a pit cannot be built on a site with a high aquifer. The base of the tank should be located at least 1 m above the GWL.
An approximate calculation of the volume of a sewer well without a bottom can be done, taking into account the average standard: 0.5 m each3 per person for his seasonal or year-round residence in the house. The average depth of the structure is 2-3 m. It is not recommended to make a deeper well, since the sewage equipment does not serve such cesspools.
When performing calculations, the following circumstance should be taken into account: the pumping of sewage from the cesspool is performed when it is filled not to the top, but by 2/3. Therefore, it is advisable to make the working volume of the tank a multiple of the volume of the cistern of the cesspool vehicle. This will help save money, since such services are paid only for the exit, and not the amount of waste pumped out. Otherwise, you will have to spend money for the removal of a small remainder of the effluent at full price.
The location of the filter pit must comply with the accepted standards. According to SNiP, such structures are built no closer than 5 m from a residential building and 20-25 m from a well or a well with drinking water.
This is dictated by the possibility of the risk of contamination of the soil or source by runoff. Most often, such a danger occurs in the spring during the flood season or as a result of mistakes made during the installation of the sewage system.
The more hygroscopic the soil has, the more intensively drains are absorbed into it. This circumstance, in turn, tightens the requirements of the standards, which must be adhered to when designing a technical well.
When asked whether it is possible to make a cesspool without a bottom in clay soil, the answer is unambiguous - it is impossible. This is due to the low filtering capacity of this type of soil
When installing a filter well in clay sand, the rate of penetration of liquid into the ground can be increased by using perforated rings. In this case, you get a version of the container without a bottom, but with a permeable body.
If it is planned to use a sewage truck with a tank to pump out wastewater from the cesspool, when designing the structure, a convenient approach for wheeled vehicles should be provided for. A distance of no more than 4 meters is allowed between the car and the drain pit. The smaller it is, the faster and easier it will be for the sewer workers to do their job.
Materials for a leaky cesspool
Materials for a leaky sewer well can be concrete and products made from it, wood, plastic, old tires, bricks, etc.
Masonry brick cesspool takes a long time and comes out expensive. This option can be considered if the owner of the site has at his disposal the required amount of material that is not planned to be used for other needs.
Of course, the beauty of the masonry of the pit walls does not really matter, but you should not use completely defective bricks. After all, the masonry will work in an aggressive environment of drains, which have a destructive effect on the walls.
Suitable instead of bricks gas silicate blocks… They are larger in size, so the work can be completed faster.
Woodfor the same reason, it is not the best choice for the construction of a filter well. The boardwalk will have to be repaired annually.
Construction from monolithic concrete is highly reliable. To create it, at the initial stage, formwork and reinforcement will be required. At the base of the monolithic well, a free cavity is left for the device of a bottom filter made of sand and gravel.
The most popular cesspool materials are factory concrete rings… But they must be of high quality. Chips and cracks on such products are unacceptable. If permeable walls are planned in a cesspool made of concrete rings without a bottom, perforated products can be taken. These concrete rings are also commercially available.
Plastic tanksusually used to install sealed drain pits. However, if a filter hole is made in such a container, it can then be used as a technical well without a bottom. Due to the fact that plastic does not differ in large weight, it is recommended to make the installed container heavier or attach it to an anchor - a concrete blank. Then, in winter, an empty tank will not displace the frozen soil outward, and in spring it will not float up in a flood.
A very simple option is a well from old tires… For its construction, you will need to dig a hole of the desired size and put the used tires in a pile. They will protect the excavation from collapse, and the external soil from the penetration of sewage into it. Tires must be stapled together. The joints between the products are sealed with plumbing sealant. At the bottom of the resulting well, a sand-crushed stone filter should be made. The work itself is not difficult, but you need to be aware of the short service life of such a pit and its high permeability.
Cesspool installation technology without a bottom
Since a filter pit made of concrete rings is the most popular option for such structures, it makes sense to study it in more detail.
The general plan of action is as follows:
- Make pit markings;
- Dig a pit;
- Mount rings;
- Lead a sewer pipe to the well;
- Make an inlet and insert a part of the pipe through it into the container;
- Seal all joints;
- Perform waterproofing of the surfaces of the well;
- Install a filter at the bottom;
- Backfill the sinuses of the excavation with soil;
- Install the overlap and cover on top;
- Decorate the top of the building.
For manual digging of a pit for a cesspool, you will need a shovel and bayonet shovel, for excavation - a bucket with a rope and an assistant at the top in order to lift the excavated soil. The first ring must be installed according to the markings, climb into it and dig from the inside. During operation, the ring will gradually lower to the desired mark. The rest of the products need to be mounted with a crane as the well deepens. If you carry out excavation with an excavator, their speed will increase significantly, although it will cost more.
A trench intended for laying a sewer pipe must be dug with a slight slope of 2-3 cm / r.m. towards the cesspool to ensure gravity drainage of waste.
If the soil freezes in winter, the pipe must be insulated to avoid the formation of ice plugs.
The inlet for it should be punched in the wall of the tank after laying the pipe in the trench. If the hole is made in advance, you can make a mistake in the height of the pipe.
When constructing a cesspool without a bottom, the joints of the rings and the place where the pipe is inserted should be sealed with a solution, and then the entire surface of the structure should be covered with a coating waterproofing. It will protect the structure from external and internal water influences and extend the service life of the structure.
To make a bottom filter, you will need river sand, crushed stone or gravel. First, the bottom of the well must be covered with 300 mm sand, then with two layers of crushed stone of the same thickness. The coarse fraction of the backfill should be on top, the small fraction - on the bottom.
After that, you can proceed with the installation of the floor. A concrete slab of the appropriate configuration is suitable for this purpose. The plate should be equipped with an opening sufficient not only for the hose of the sewage pump, but also for penetration into the human container for examination of its condition after emptying.
The inspection hatch must be closed with a lid.Then the stench will not bother others. If the cover is made double, it will be able to protect the area from unnecessary odors and sewer drains from freezing in winter.
In order to preserve the landscape of the site, it is recommended to fill the overlap with soil, leaving its cover free. Its height above ground level should be 300 mm.
When operating the finished drain pit, you only need to periodically observe the increase in the level of wastewater and pump them out in time. If the calculations and installation of the structure are done in good faith, it will need to be cleaned only 2 times a year.
During maintenance of such a cesspool, the bottom filter is flushed or replaced. Such work is dangerous, therefore, the insurance of the performer in the person of a partner who is constantly at the top is required.
How to make a cesspool - watch the video:
Regardless of whether a cesspool without a bottom is made from a barrel, tires, brick or concrete rings, in any case it is a useful structure. During its construction, it is important to adhere to technology, and during operation - to sanitary standards.