Table of Contents
Guide to independent design and construction of septic tank.
Construction of septic tank in owner-occupied dwelling
The lion share of private building in the small cities and rural lands of manned open spaces of our extensive fatherland has (and will never have) no central sewerage. But its absence does not mean at all that citizens have to reconcile to “conveniences in the yard”. More likely, on the contrary. For example, in the richest country of the world, the USA, country settlements with spacious houses, pools, terraces and garages on 2-4 machines are not channeled. All of them are supplied with local sewage treatment plants (biofilters). And availability and location of obligatory green lawn quite often is defined by the underground field of filtering: it is not recommended to plant trees and bushes on this place.
Technically local sewage treatment plant (septic tank or aerotenk) — quite simple construction. Correctly calculated and constructed, it without problems will provide effective waste water treatment for many years. That operation of the biofilter managed cheap and did not bring efforts, the owner of the house, the designer or builders have to understand accurately as why they do.
Cleaning of drains is provided by our very little assistants — useful bacteria. They with big appetite process organic pollution, oxidizing and decomposing them to the simplest components. As a result of their work clear water, the mineral deposit rich with microelements, useful to growth of plants, and evil-smelling gas turns out. Two types of bacteria live in sewage treatment plant: anaerobe bacterias and aerobes. The first do not need oxygen, perfectly feel in stagnant water, living in all its thickness. The second, on the contrary, cannot do without oxygen. In stagnant water they can live near only to surface, there is dissolved gas.
Because oxygen is used by them as the catalyst in exchange processes, metabolism of aerobic bacteria much more intensively. Respectively, they decompose organic chemistry much quicker.
Septic tank and aerated lagoon — distinctions
Depending on dominance of these or those species of bacteria biofilters happen two types:
- Septic tank (the correct definition — putrefactive septic tank) — simple construction where cleaning is made, mainly, by anaerobe bacterias. Liquid in septic tank poorly flowing, Wednesday oxygen-free. Speed of cleaning is low.
- Aerated lagoon, unlike the previous type of the filter, shelters aerobes. To provide water saturation with oxygen, drains aerate and mix, force air by means of the compressor. It raises the price of system and complicates its operation, but gives prize in efficiency.
In septic tank and aerated lagoon there is, in fact, the same process. Difference only in the speed of decomposition of organic chemistry. In “fast” to aerated lagoon cleaning happens almost five times more intensively, than in “slow” septic tank.
Respectively, at higher speed of cleaning, reservoir volume with aeration can be five times less.
Sanitary standards at construction of septic tank
The main document regulating norms of construction of septic tank for us “The sewerage and outside networks and constructions”. The sewage treatment plant executed according to norms if the construction permit of septic tank does not provide other option. Perhaps, it is necessary to provide simple calculation.
- Location. The sewage treatment plant should not be located closer than 7 meters from the well of potable water and at distance not less than 8 meters from the house. We recommend to place septic tank closer to the road and entrance on the site to provide if necessary entrance to the cesspool machine. And to drill the well far away, in the yard from reverse side of the house.
- Extent of cleaning. The nature of withdrawal of the cleaned drains depends on this indicator. To dump water in soil, extent of cleaning has to make not less than 65%. In reservoir or on the surface of the soil, in ditch — from 98% and above.
To choose septic tank or aerated lagoon?
Ready factory biofilter or capital reservoir? Answers are ambiguous.
The cost of the strengthened plastic reservoir is almost always higher, than tanks which can be built independently. Besides, reservoirs are quite small and need additional after-treatment: the filtering trench or the field. It is money too. And life cycle of polymeric barrel, at least, will not be higher, than at concrete structure. Aerated lagoon, especially with forced modulation of drains between cameras, will manage still unlike more expensively. Besides it is necessary to consider expenses on the electric power and equipment maintenance: compressor and, perhaps, pumps. Besides without availability of system of reserve power supply installation the aerated lagoon does not make big sense: in case of lack of aeration within 6 hours about 30% of aerobes, day — nearly 100% perish. Complete recovery of useful microflora and productivity the aerated lagoon will take not less than two months.
If the level of underground water is too high, water cannot be dumped in soil. In this case it is necessary to equip aerated lagoon, to deeply clean drains to 98% (the putrefactive septic tank will not cope with such task at all), to take away them in ditch. It is allowed and it is even recommended to use such water for watering of kitchen garden and garden. Cucumbers, tomatoes and lawn grass will only be glad to natural and useful fertilizer. In this case the factory hermetic reservoir equipped with the corresponding set of the equipment will be the rational decision.
Availability on the site of the place — one more factor defining design of sewage treatment plant. The “correct” septic tank will demand the considerable area. If there is no place, it is necessary to put the compact ready biofilter. Will occupy absolutely small area aerated lagoon.
In terms of ecology, of course, it is more preferable to establish aerated lagoon. Though, at removal of liquid in soil, it is not crucial: soil bacteria also perfectly oxidize organic chemistry.
Conclusion: at the limited budget of building, low level of underground water and availability of the necessary place on the parcel the construction of normal septic tank without aeration using traditional construction materials will be the most rational option.
What to build septic tank of?
Structurally the biofilter — one or several tanks, not always hermetic. Theoretically, does not matter what to build them from. The main thing that they were strong, long-lasting and did not pass storm water from surface. The most widespread options:
- Septic tank from old tires. Use tractor, it is more also from the truck, less. Stack pile, one on another. Quite often internal borta cut. Not to allow penetration of rain water into capacity, from above tires should be isolated roofing material, film, concrete or other improvised materials. The cover and the hatch are done of wood deck, metal sheet and that under hand will get. Advantage: almost free of charge, if there is access to rubber. Shortcomings: the general hlipkost and fragility, distortions at the movement of soil, difficult it (is almost impossible) to provide tightness, limited volume.
- The written-off iron barrels. Also reservoirs and other valuable iron stuff. Advantage: free of charge or very cheap. Shortcomings: metal in the earth quickly sgniyot, often insufficient volume.
- Eurocubes for septic tank. Plastic tanks with jellied mouth and in metal framework of cubic form with meter dimensions. The written-off cubes from under reactants occasionally can be bought for ridiculous money. It is simple to cut through in plastic walls of opening, to insert there overflow and outflow pipes, to cover slots with silicone sealant and to envelop joints the construction reinforced adhesive tape. It is possible to dewater in the filtering trench. However, it is difficult to provide stability of such design. In cold places can squeeze out small cubes from soil by forces of frosty rebound in the winter if not to dig them lower than frost depth. Can squeeze thin walls. Besides volume is small and all the same it is necessary to think out something for service of tanks through narrow mouth. Such execution will be suitable for the budgetary giving more, than for good country house.
- Monolithic steel concrete — great option. The main complexity and labor costs consist in production of timbering. Expenses are justified if nearby there is no house-building plant from where it is possible to bring ready rings of wells.
- Precast factory reinforced concrete constructions for septic tank. It can be also the cabin rejected dignity of those used in large-panel housing construction, the second-hand telephone wells bought by chance. However, the best option — standard steel concrete rings of wells with a diameter of 1; 1.5 or 2 meters and covers to them. With use of standard rings we will also tell about construction of septic tank in more detail.
- Construction of brick septic tank. The brick of domestic production, unfortunately, has low frost resistance, high water absorption and is of little use for construction of underground tanks. But if it is possible to get new or well burned corpulent ceramic brick which has remained from dismantling of old constructions why and is not present? It is possible to use also concrete brick. The most rational configuration of such reservoir — cylinder. The round form in the plan holds loading better and demands smaller consumption of material. If to buy brick qualitative, new and for overall cost, such septic tank will be more expensive steel concrete.
How to calculate the total amount of septic tank?
It is recommended to accept when calculating on one person 200 liters of drains a day. It is offered to provide the total capacity of the reservoir of not less three-day drain. The family with two children contacts 800 liters a day. Three days — 2400 liters. However, sanitary standards do not allow to take away domestic sewages from putrefactive septic tank in soil earlier, than in 14 days after receipt them on cleaning. This time is necessary for 65% cleaning. Already we receive 11200 liters. In practice today we began to spend water much more economically. Without leaving the crane opened without need, it is quite possible to invest in half of the recommended expense. The sewage treatment plant in 6-8 m3 will quite meet the moderate needs of average family. If there is pool, big Spa bathtub and other miracles of plumbing fixtures, volume needs to be increased. In the presence of the field of filtering the volume of septic tank can be reduced by third. If to equip the reservoir with the compressor, we will receive aerated lagoon. The spaciousness can be five times less. The volume of the reservoir is considered from bottom to inlet pipe.
How many to do cameras in septic tank?
It is allowed to construct septic tank at receipt of drains to 1 m3 a day single-chamber, up to 10 m3 — two-chamber, more — three-chambered. In each of cameras not dissolved particles are separated, it raises extent of cleaning at the exit. Besides drains in the last reservoir are in multichamber capacity longer and are exposed to bigger biological cleaning. But to us important not only not to break ecology, but also to minimize costs of service. All not dissolved pollution (high-melting fats, cellulose from toilet paper, coffee thick, mineral deposit, silt) will settle in single-chamber sewage treatment plant on surface of the filtering bottom and quickly will cork it. The filtering trench too soon will be hammered. In multistage design the main pollution, hardly subject to processing, will remain at the bottom of preliminary reservoirs. Time in their half a year can be pumped out. And on drainage course of the soil almost clear water will arrive. Answer to question of the number of cameras is as follows: the more the better. Optimal variant three. One camera with filtering through bottom — the unprofitable decision. Perhaps, in several months the system will be silted, it is necessary to clean the absorber or to regularly order the cesspool machine. Additional expenses on increase in number of cameras will pay off afterwards a hundredfold at the expense of low expenses on service.
Technology of mounting
There are two options: manually and by means of the crane.
Construction of septic tank from concrete rings:
- Manually. Rings drive to the place of mounting, establish into place and choose soil from below, gradually lowering ring. When the lower section falls level with earth surface, on it establish following. It is necessary to control constantly horizontal position of bottom during removal of soil, otherwise the ring can warp. If it falls hardly, the outer surface can be spilled water, it will soften soil and will work as lubricant. Two healthy men will be able quite to be controlled with meter rings. One-and-a-half-meter four six hardly will drive and will put. Construction of septic tank from concrete rings the hands it is cheaper, than with the equipment. But at manual mounting you should not contact two-meter elements.
- By means of the equipment. To employ separately the crane expensively. Will cost cheaper in advance to choose ditch as the bulldozer, and to deliver rings on service platform with the manipulator. They weigh slightly, from their board it will be possible to mount into place at once. Having correctly planned works, the septic tank can be made for couple of days.
Whether the waterproofing is necessary?
Quite often concrete reservoirs paste over outside with rolled waterproofing. In it there is no big sense. Much more important carefully, good solution to fuller joints between sections. If there is a strong wish to isolate capacity, it is better to make it from within, having caused with brush inexpensive cement waterproofing structure. It is not necessary to dry concrete, it turns out cheap and quickly.
Distribution of volume on sections
The second section — metatenk has to have the largest volume. In it occurs the main biological processes. It has to have about 50% of total amount. The first in which will settle large particles and fatty films and the third, clarifier — approximately on 25%. It is optimum. But if compartments are identical, no trouble happens. Just extent of cleaning will decrease by several percent.
Internal volumes of rings:
- meter — 0.7 m3;
- half-meter — 1.57 m3;
- two-meter — 2.8 m3.
If to arrange the first camera from two meter elements, the second of two-meter, and the last from one-and-a-half-meter, we will receive about 10 sq.m. As cameras will be filled with drains only to mark of inlet pipe, volume gross will be required 8-9 m3.
To each section access has to be provided. Reservoirs of septic tank can be dug rather deeply therefore from cover of well it is necessary to lay out brick or to concrete rather wide mouth on which the hatch will be installed. Pig-iron are expensive now, polymeric is several times cheaper.
Drains take away in soil in two ways:
- Through bottom of the last, absorption, well. In the first sections the bottom is concreted, in the last fill crushed stone layer in 30-40 cm. In walls of the lower section it makes sense to nasverlit more openings with a diameter of 10-12 mm, will absorb also walls. Drains go practically to any soil, even pure clay.
- Through the filtering trench or the field of filtering. The device of such system — subject for separate conversation. It is more effective, but also is more expensive than the previous option. One of difficulties consists in the large volume of earthwork operations and need to have delivery pipes lower than frost depth of soil.
It is desirable, but it is optional to dig in the giving sewage pipe it is lower than frost depth. In septic tank warmly if it is located not further 10 meters from the house, giving can be dug on half-meter above freezing mark. However, useful will be to warm pipe and mouths of reservoirs material with low water absorption. For example, polyfoam. On overflow pipes between sections it is necessary to install in order to avoid overflowing of large particles T-couplers on both sides. The first modulation has to be located below entrance, the subsequent below previous. The horizontal bias of pipes should not be too big, optimum value — 2%.
The separate ventilation pipe as recommend in some grants, is not necessary at all. Ventilation is perfectly carried out through thinnesses and special opening in the hatch. Air gets into septic tank, passes on pipes in the house sewerage, comes out through the strut brought to roof. It is not recommended to reduce diameter of strut at the exit.
Problem of fetid odor
The septic tank should not stink. Availability in few months after the first loading notable at the closed hatch of fetid odor speaks about the unsuccessful environment for bacteria. It can come from availability in drains of substances, poisonous for microflora. The volume of sewage treatment plant is less, the concentration of “poisons” is higher. Fecal drains to bacteria are not terrible. Laundry detergents, disinfectants, salt dumpings of powerful filters for softening of water and plums from modern condensation gas boilers cause them loss. Of course, it is impossible to lower organic solvents and other chemical muck in the sewerage. The rational decision will be to take away drains from these devices in separate small soakaway, it can be the simple barrel dug to the earth. By the way, stench from badly working aerated lagoon 10 times more, than from septic tank: Wednesday in it constantly mixes up, and the volume of the emitted gases are more.
Correctly calculated and constructed septic tank practically does not need service. Once a year it is worth ordering the cesspool machine and to pump out deposit from bottom. Sometime, very at a distant day, the absorber will be silted. It is necessary to replace layer of crushed stone and 30-40 cm of soil. Or, without touching well, to add to it the filtering trench.
Complete set of materials: will cost rings, covers, brick, hatches, pipes about 1000 on the design considered in article. The equipment and work — is not considered.