Insert in a concrete septic tank: waterproofing with a plastic insert

The massiveness and external reliability of concrete rings attracts homeowners. Structures of concrete submerged in the ground easily resist the pressure of soils, they are not threatened by corrosion. Concrete stone is durable, waterproof and durable.

Septic tanks, recruited from reinforced concrete rings, are built quickly, but after 10-20 years they begin to flow... This problem can be corrected by inserting into a concrete septic tank or external sealing of the walls of the well. Which solution is better? Let's try to understand this material.

Causes of leakage of concrete septic tank

Monoblock and prefabricated structures made strictly of high-quality concrete are used to build the well - not lower than B-15. Moreover, the brand for water resistance should be at least W8. Otherwise, the walls of the septic tank will pass water in both directions, regardless of the quality of the sealing of the joints.

Errors in the setting of the rings, lowered on the slings of a truck crane, cause not only the curvature of the seam line between the prefabricated elements. When assembling an underground tank from reinforced concrete rings high risk of hitting each other.

From the first time, it is almost impossible to set the rings, you have to raise and lower them two or three times. Each w / b ring weighs about half a ton. The blows of the upper precast element on the lower segment do not pass without a trace - cracks and chips are formed.

Ground heave is often underestimated by homeowners. As a result of heaving the rings of the precast concrete tank are shifted. Groundwater and flood waters enter the septic tank through gaps, significantly increasing the level of wastewater in the sewage treatment plant.

When the sewer structure is flooded, the probability of the release of untreated sewage to the outside through leaking sections of the barrel is high. As a result, contamination of the surrounding soils and the waters they contain will occur.

The high level of groundwater is peculiar to the territories of the middle zone of the Russian Federation during the flood flood period. It is especially high (less than 500 mm) in areas removed from the marshy state by land reclamation measures. To achieve waterproofing of the casing of a concrete-concrete septic tank in the vicinity of groundwater is almost impossible.

With insufficient or inefficient insulation of the upper part of the underground concrete tank, its protruding part will be destroyed in about 10 years. Critical defects will cause a change in freeze and thaw cycles. Moisture penetrating into the pores of the concrete freezes and expands, forming abundant microcracks. The result is one - rain and flood water will flow into the septic tank.

To eliminate leaks necessary waterproofing concrete septic tank from the outside or from the inside. The use of waterproofing compounds for the repair of an operating reservoir is permissible only outside, since most of the water-protective compositions are destroyed by contact with sewage.

The only solution for internal waterproofing is an insert in a concrete septic tank that minimizes the amount of work inside the well. To give an idea of ​​the nature of the work, then we will consider both types.

Alternative to plastic inset

First you need to empty the repairable reservoir tank or a septic tank, pumping out the contents with the help of a team of vacuum trucks. Service for pumping a septic tank, removal of its contents is provided by utilities and private companies. It is cheaper to negotiate directly with the nightman of municipal services.

Cesspool transport will need access to the object of work. And the distance of the entrance will be the less, the shorter the transport sleeve of the machine. Its permissible length is up to 180 meters and even more - up to 500 m, if it is a high-pressure polyethylene sleeve.

Pumping septic should be done by trained specialists, amateurs will not cope. Septic tank cleaning works are performed by a special pump - sewer (fecal).

Waterproofing the seams of a concrete septic tank

To seal the gaps between the concrete rings of the well, it is necessary to get to them outside the structure. It is necessary to dig a ditch around the septic tank to a depth that allows working with joints between reinforced concrete sections.

Accordingly, the more rings in the structure of the tank - the deeper the ditch will have to dig. Ditch width - not less than a meter. In a narrow ditch it will be difficult to work.

Having dug up the walls of the septic tank, you need to dry them. To top waterproofing works dark spots on the concrete walls should not be. The seams must be cleaned from the accumulated debris and soil, exposing the cavity to at least 70 mm depth.

If rain is expected, cover the well and the ditch dug around it with a moisture-proof material (plastic wrap, tarp, etc.).

To fill the seams requires a well-washed clay and plaster grater. Clay should be kneaded with feet in a pelvis or other similar container. The packing of joints between concrete rings with soft clay is inefficient - its structure will be uneven, including voids that will allow water to pass through.

The sealing of the external joints between the concrete sections of the septic tank can be performed with a cement-sand mortar mixed on the liquid glass. The composition of the mixture: liquid glass, cement and seeded fine sand in a ratio of 1: 1: 3.

Prepare the mixture should be small portions - when adding liquid glass solution quickly hardens. The seams are filled with this solution using a spatula.

Butt mortar is also prepared from a mixture of cement with PVA construction glue. Proportion: 5 parts of cement to 1 part of PVA. After filling the solution with stitches, two or three layers of liquid glass can be applied on top. This will strengthen the waterproofing.

Before filling the joints with cement mortar, it is necessary to treat them with a primer. For septic tanks used technical priming materials. For example, such - one part of bitumen into three parts of gasoline.

There are pores in the structure of the concrete stone, because the septic tanks collected from the reinforced concrete rings let the water through, albeit in small quantities. When freezing, the water in the pores will crystallize, increase in volume and eventually destroy the monolithic compound.

Installation of roll waterproofing

Having completed the work on the seams of concrete rings, proceed to the formation of the surface layer of protection of the tank from moisture. If clay was used for the joints, then roll materials should not be applied on top of them - the clay plaster will be broken off when the glue mastic cures.

The outer surface of the concrete well is required to be completely covered with a primer, for example, asphalt-gasoline. This will improve the bonding of the roll waterproofing to concrete rings. Then the walls are coated with preheated tar mastic, the roll-bituminous material is glued in two or three layers.

Note that the bitumen mastic for waterproofing the walls of a septic tank with rolled materials is not suitable - it cracks when it cools.

To reduce or eliminate the likelihood of soil heaving around the concrete shaft, apply sand and gravel backfill (40% sand, 60% gravel). It is filled with a ditch, previously opened around an underground tank for repairing the seams between the well rings.

If under a layer of soil sand lies without clay inclusions, gravel or rubbly deposits, the backfill can be carried out with the ground of the blade formed during the development of the pit around septic tank.

Plastic insert for waterproofing septic tank

Regardless of the depth of the well and fame, or the uncertainty of leaking zones, a plastic cylinder inserted into a septic tank is capable of closing them at once. To begin work on the installation of the insert, it is necessary to empty the sewage tank, causing a vacuum truck. Then you need to wash the walls and bottom of the well with a stream of water from a hose supplied under pressure.

Manufacturers of modular rings and full plastic tanks produce them ready-made, of various diameters and heights of the walls. It is possible to order non-standard containers and rings, if the diameter of the repaired septic tank does not match the parameters of serial plastic rings (too large or small). It is optimal if there will be a gap of 50–100 mm between the walls of the insert and the septic tank, no more.

To restore the tightness of a concrete septic tank, plastic rings with 5 mm wall thickness are needed. There is no need for thicker walls - the main concrete walls of the old well will provide ideal protection. The reinforcement ribs, made around the perimeter of the plastic rings, will retain the rigidity of the well insert when sewage flows.

Modular rings are connected to each other with a slot insert, welding or screwing. The weight of one section of the plastic insert (height 1500 mm, external diameter 950 mm) is about 25-30 kg. To assemble the insert correctly, it is necessary to assemble its modules outside the well. A fully assembled insert is inserted into the septic tank manually (if the length is not more than three meters) or by a mobile crane.

Mounting the composite insert

When assembling plastic composite sections-rings in the tray of the lower ring is laid a regular rubber seal, put the upper section. To combine the lower and upper rings of the insert, you need to put the board across and in the center, then press it on both sides.

An important detail: the interconnected insert segments must be placed horizontally before pressing the board. Otherwise, full insertion of the upper section fasteners into the bottom tray will not be achieved.

The modules of the rings, the assembly of which is performed by screwing, are combined into an insert of the required height inside the well or outside it. The first option is suitable if the septic tank is shallow. Although it is more convenient to perform the screwing of the sections on the site, and then to lower the assembled insert into the sewage tank.

Regardless of the method of combining plastic rings, the groove between them is additionally processed with silicone mastic. It is applied on both sides - external and internal. Of course, with the years of operation of the septic tank, the grooves in the insert will automatically fill with silt and will only increase their waterproofing properties.

However, in the first months and years of the repaired septic tank, the silting will occur slowly. Therefore, the use of silicone for the seams between the sections is a necessary solution.

The bottom module is the base of the entire insert, it is necessary to seal the septic tank. Before installing it in a concrete well (or placing a fully assembled tank), make sure that the septic tank bottom is durable. The required concrete thickness at the bottom of the sewer well is 150 mm.

When the assembled plastic insert is lowered into a concrete tank, it should not be allowed to be significantly deflected - the module attachments may be broken. Installation in the well of the insert with the number of modules more than three is the most correct to carry out the suspension on the crane crane sling.

Judge for yourself: the approximate length of the three-section well insert is 4.5 m; weight - about 100 kg. On the hands of the lower plastic construction of such length and weight in the septic tank will be difficult.

The final stage of assembly of modular construction

If the protrusions of the pipes in the repaired septic tank are too long and will interfere with the installation of the plastic insert, they must be cut off. The inlets of the drain pipes into the cavity of the insert through its walls are made through sealing cuffs and rings, with the processing of the joints with silicone.

In plastic rings, modules of some manufacturers are marked sectors (trays) for input sewer pipe. Regardless of whether or not such designations exist, it is necessary to cut a hole in a certain section using a jigsaw to insert a pipe.

There is a gap between the walls of the plastic tank and the old concrete septic tank - it must be filled. A cement-sand mixture is prepared in a proportion of 1: 5. Her backfill in the pier is dry.

Approximately from the middle of the depth of the reservoir it is necessary to begin light tamping of the cement-sand dumping, using a long wooden pole. The pole must be kept strictly horizontally so as not to touch the walls of the plastic well.

For complete confidence that the insertion channel does not move during the dumping and tamping process, water can be poured into it - at first, not more than a third of the tank. As the gap between the walls of the septic tank is filled, water must be added to the well. It should be infused so that the level was 200 mm above the current level of dumping.

Installing a plastic headband

The upper section of the plastic insert for the septic tank is called the neck. In principle, its installation on a restored sewer well in a private compound is not obligatory. But only in the case that the flat ring of the concrete headband from the old septic tank is intact - there are no cracks or loosening sections revealing the reinforcement.

If there is no need for mounting the neck, then the upper edge of the plastic well insert must be brought 120 mm above the ground level, not more. The height of the reinforced concrete slab, manufactured for the headband well according to GOST, is 200 mm.

The upper edge of the plastic insert should not stand for it. It is necessary to lay in the gap between the outer edges of the insert and the upper concrete slab seal - cabol (resinated rope).

The installation of the neck module will allow you to do without laying the concrete ring-headband. On the plot of a private house, this is permissible if the septic tank is not under a pedestrian walkway or car park. It will be enough to close the neck. plastic hatch of the manufacturer that produced this set of modules for the repair of the well.

Classic plastic waterproofing

If it is possible to install a monolithic cylindrical insert made of polyethylene into the barrel of a sewer well, it is better to use this method. Work on the installation of waterproofing will be carried out much faster and with the lowest labor costs.

In the manufacture of inserts of this type, polyethylene is used - a material that is completely insensitive to the direct effects of an aggressive environment. The shell wall thickness is 8 mm, which excludes accidental damage to the structure during transportation and installation.

Before immersing the insert into the trunk of a concrete septic tank for entering and exiting sewer pipes in the walls of the hull, holes are drilled exactly according to the outline of the connected branches of communications. Passages seal or scald around the perimeter. The gap between the insert and the concrete walls of the septic tank is filled with concrete solution.

The choice of waterproofing method

Classical solutions for isolation from leaks of a sewer well, built of concrete rings, are quite effective. However, sealing of joints, treatment of tank walls with bitumen mastic and similar measures are only suitable for septic tanks under construction. Those. for new underground tanks that have not yet been commissioned.

One-sided waterproofing of external walls, acceptable for septic tanks with years of work, will reduce the leakage of sewage into the ground. The strength of waterproofing coatings on the external walls of a concrete well will remain over 10 years, but only under the condition of professional repair work, the use of quality materials.

Plastic ring modules are produced at the enterprise, i.e. in the conditions of the shop. They are designed specifically for the repair of wells, the construction of new recessed tanks. A plastic insert placed in a concrete well is not related to its construction.

Therefore, its tightness does not depend on the degree of wear of the repaired septic tank; it will be only a protective case for a plastic reservoir.

Own operational qualities of the plastic capacity intended for a waterproofing of a septic tank are rather high:

• small weight (in comparison with reinforced concrete);
• full tightness;
• low thermal conductivity;
• resistance to abrasion, to aggressive environments;
• long service (over 40 years);
• high impact strength, resistance to mechanical stress;
• resistance to ultraviolet radiation;
• frost resistance;
• simple installation (except for the welded assembly principle of sections).

Therefore, the choice in favor of the polyethylene insert is most justified. Getting rid of problems with a sewer well flowing in a suburban area for decades is a great option! We also recommend reading our other article on waterproofing methods concrete septic tanks.

Conclusions and useful video on the topic

In this video, plastic modules can be viewed from all sides and even touch:

Video about the assembly of the well from plastic elements at the place of its installation:

A plastic plastic well completely solves three problems: leakage through joints, through cracks and through the walls of concrete rings. However, the price of such repairs will not be cheap. The cost of a 1.5-meter segment insert, with a diameter of 950 mm and 5 mm wall thickness is approximately 15,000 rubles. However, decades without sewer "surprises" are worth it.

You are going to install a plastic insert in a concrete septic tank, but do not know where to start? Or have experience in conducting such work? Please share your knowledge with our readers - leave comments in the block below.