Do-it-yourself septic tank waterproofing

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Do-it-yourself septic tank waterproofing
Do-it-yourself septic tank waterproofing

The principle of waterproofing a septic tank, its purpose, materials, methods and features of work. Preparation of structures for insulation, internal and external surface treatment, sealing and protection of joints in concrete structures. Waterproofing a septic tank is a necessity due to the risk of contamination of groundwater by its contents. The problem of seepage of sewage into the soil through microcracks in the walls of such a tank is especially relevant for concrete and brick structures. Our article is about the correct implementation of their isolation.

The need to isolate the septic tank

Septic tank waterproofing
Septic tank waterproofing

Many people perceive the concrete rings of wells or their masonry as something solid and indestructible. This is largely true. But if the structure operates in an aggressive environment, corrosion processes can cause a loss of its bearing properties.

An aggressive environment for a septic tank should be understood as its contents and soil waters, which contain acids or alkalis, but in low concentrations. The destructive effect of sewage manifests itself much faster than the effect on an underground structure of groundwater. Therefore, waterproofing the septic tank from the inside is a top priority. Ideally, it is better to defend it from both sides.

The waterproofing of the septic tank, made at the stage of its construction, ensures the durability of the structure and the preservation of its strength. The integrity of the structure relieves the soil of the summer cottage from contamination by microorganisms present in the sewage, and the air from the smell of the toilet.

Thus, the waterproofing of a septic tank has a dual purpose - to protect its structure from destruction and protect the soil from the penetration of sewage into it.

The main methods of waterproofing a septic tank

Penetron Admix for septic tank waterproofing
Penetron Admix for septic tank waterproofing

For waterproofing and sealing sewer septic tanks, a large set of tools is used, the main ones are:

  • Bitumen based mastics … When applied hot, pure bitumen has only one plus - its low cost. The rest of the bituminous coating leaves much to be desired: it quickly cracks, and after several cycles of seasonal freezing and thawing, it flakes off safely. Bitumen with polymer additives works much more reliably. This mastic can be applied cold, which greatly simplifies the insulation process. Polymer additives increase the chemical resistance and life of the coating. For their manufacture, rubber and polyurethane are used.
  • Polymer-cement coating … It is more expensive than bituminous mastic. The composition can be applied with a wide brush. For good insulation, two layers of coating are required. There is no need to wait for the previous layer to dry before applying the second one. Therefore, work will proceed quickly. The service life of such a coating is 40-50 years. The non-shrinking coating of the Penetron Admix or Penecrit type is especially good.
  • Polymer insulating compound … It is the most expensive, but very effective. Possesses high elasticity and is used to protect unstable wells, which are characterized by frequent deformations, accompanied by the appearance of new cracks. A mixture of the TechnoNIKOL brand has an optimal ratio of cost and quality. A coating made with this material can last for over 40 years.
  • Penetrating waterproofing … It is not one of the cheap formulations and requires strict adherence to the application technology. Penetrating into the pores of the walls of the septic tank, the mixture forms crystals under the influence of liquid. The structure becomes waterproof. If a new crack appears in it, a self-healing effect occurs: the liquid that gets into the problem area again activates the crystallization of the mixture. "Penetron" or "Lakhta" are considered to be expensive formulations of penetrating action, and "Elakor-PU Grunt-2K / 50" - to the cheaper ones.
  • Injectable mixtures … They are too expensive to isolate septic tanks and are therefore used if other materials do not work. This is extremely rare. The repair mixture is pumped into pre-prepared holes in the walls of the structure through special injectors. The injection material can be polyurethane and epoxy resins, water glass, acrylate, etc.

There are three more ways to waterproof a septic tank made of concrete rings or bricks:

  1. Cylindrical plastic inserts … When used, the well takes on a glass-in-a-glass appearance. The gap between the wall of the well and the insert is filled with concrete. The finished structure can serve for more than 30 years and is a model of reliability, since it guarantees the complete tightness of the septic tank even if its rings are displaced as a result of heaving of the soil.
  2. Clay castle … With its help, you can protect the septic tank from melt and rainwater. The top of the gap that remained after the installation of the septic tank between its rings and the external soil is filled with clay. But before that, the soil around the well must settle and become dense. Clay is laid in portions, carefully ramming each layer. Leaving voids in an earthen castle is excluded, since otherwise the desired effect cannot be achieved.
  3. Mechanized plaster … To implement this method, you need a cement gun. With its help, the walls of a concrete septic tank are covered with two thick layers of waterproof cement. The first layer is dried in the heat, moistening it every 10 hours with water, and the second layer is applied on top after the previous one has set. Labor intensity and the need to use special equipment are the disadvantages of this isolation method.

From the above analysis, there are three most suitable methods for self-waterproofing septic tanks. In our opinion, this is the use of bitumen-polymer mastics, penetrating compounds and polymer-cement coating. In concrete wells, the seams between the rings are the most vulnerable point. It is through them that the first leaks occur. Sealing of the seams cannot replace the correct fastening of the rings of a concrete septic tank. If their design does not provide for special mounting grooves, steel braces must be used.

How to properly waterproof a septic tank?

The design of the septic tank initially assumes the presence of 2-3 reservoirs, connected in series with each other by overflows. The last container, which serves as a biofilter in the system, does not need to be isolated. From it, purified wastewater in a small amount seeps into the ground, without bringing it any harm. Of great importance is the protection of any of the septic tanks from the penetration of atmospheric precipitation. It can be provided with the help of clay locks and the sealing of the joints between the main elements of the structure.

Preparation for waterproofing a septic tank

Septic tank preparation for waterproofing
Septic tank preparation for waterproofing

It is very convenient to perform waterproofing of a septic tank at the stage of its construction. In this case, you will not have to carry out additional work.

If the well is active, first you should pump out the drains and remove the soil around it to the depth of the wall height. After this, the structure must be thoroughly dried. A sign of dry concrete is the absence of dark spots on its outer surface. For the period of work, the septic tank should be protected from precipitation.

All deposits, dirt and moss must be removed from the outside and inside of the tanks. This can be done with a steel bristle brush and scraper. After that, the walls and bottom of the septic tank must be carefully examined and defective places must be identified.

If cracks are found, they should be cut with a perforator to a width of 20 mm, a depth of 25 mm, and then cleaned of concrete dust and filled with a cement-polymer mixture. Potholes should be dealt with in the same way. In the absence of such material, it can be replaced with mortar with the addition of PVA in a ratio of 5: 1.

Reinforcement is often exposed when the concrete is diligently cleaned. If this happens, you need to remove rust from it, and then cover the metal with an anti-corrosion compound. When all the repair mixtures are dry, you can proceed to the main stage of work.

External waterproofing of a septic tank

External waterproofing of a septic tank
External waterproofing of a septic tank

The outer insulating cover should cover the surface of the technical well, starting from its lower edge and ending with the upper one. On the street during work, the temperature should be at least 5 degrees.

Most often, the external insulation of any wells is performed with bitumen-based mastics and roll materials.

The work should be done in stages:

  1. To obtain high-quality adhesion of concrete with an insulating material, the prepared surface of the septic tank must be treated with a primer. It can be prepared by dissolving one part of bitumen in three parts of low-octane gasoline. The primer should be applied with a large brush or brush.
  2. To improve the quality of insulation, all seams of the structure can be glued with rubber tape or CeresitCL 152.
  3. After the priming solution has dried, the outer walls of the septic tank must be coated with a cold-curing tar mixture. It is not recommended to use bituminous mastic in its pure form, as it cracks over time.
  4. A richly oiled surface must be covered with roll insulation from above. You will need at least three layers.
  5. All joints of the insulation must be treated with mastic, and then fill the septic tank with soil from the outside.

External waterproofing of the septic tank from groundwater should be carried out in a respirator, since the fumes of bitumen and gasoline are not beneficial to health. When the soil in the sinuses of the septic tank sags, it is necessary to make a blind area or a clay castle around the structure. This will protect the structure from the external effects of precipitation.

Internal waterproofing of a septic tank

Bituminous mastic for waterproofing septic tanks
Bituminous mastic for waterproofing septic tanks

As an example, let's choose insulation with a bitumen-polymer composition. There are several reasons for this: the material is inexpensive, you can work with it yourself, the finished coating is quite reliable, and when leaks appear, it can be easily restored.

After the surface preparation described above, the internal waterproofing should be carried out in the following order:

  • Process the inside of the septic tank with a primer, applying it with a wide brush. The composition is sold in the store and is an aqueous emulsion, which must be diluted before use according to the attached instructions. Two coats of primer should be sufficient. Dry the first layer before applying the second. The composition should be well absorbed into the pores of the walls of the septic tank. This will take 1-2 days.
  • After priming, open the container with bitumen-polymer mastic and gently mix the material with a mixer. If the mastic is too thick, it can be thinned with white spirit.
  • The prepared composition must be applied to the walls of the septic tank in a dense layer, avoiding drips. The coating must be uniform and uniform. The work must be done with a paint brush.
  • When the mastic is dry, the treated walls of the septic tank should be inspected. If areas of coverage with a violation of solidity are identified, another layer of material should be applied. After 2-3 days, the coating will dry out, and the septic tank can be used for its intended purpose.

Due to the fact that some bituminous mastics contain toxic solvents, it is recommended to use a respirator when working with them. Gloves and overalls also do not hurt, since it is very difficult to wash the mastic from the skin.

Important! All measures for the external and internal insulation of the septic tank should be carried out after sealing its installation seams, hatches and nozzles.

Circular seam protection

Cord for waterproofing circular joints
Cord for waterproofing circular joints

Most of the concrete rings that are used for the installation of septic tanks have locks made in the form of lower and upper grooves. When installing "groove in groove" on the grout, the rings cannot move in relation to each other. Such a lock simplifies vertical alignment of the well and eliminates the need for sealing ring joints.

In other cases, work should be started by waterproofing the bottom immediately after installing the ridge plate and the bottom ring. To seal the joints, you can use a cushioning cord such as "Gidroizol M" or "Barrier". It is laid between the lower ring and the bottom, and then between each pair of well shaft elements.

After sealing, the joints of the rings must be isolated from the outside of the septic tank and from the inside. A bituminous coating is suitable for external waterproofing, and AQUAMAT-ELASTIC mixture, produced by ISOMAT, for internal waterproofing.

How to waterproof a septic tank - watch the video:

It is easy to understand that waterproofing a concrete septic tank or a brick cesspool is not an easy task, especially when the structure is active. But such work is necessary to protect the structure itself and preserve the ecology of the suburban area. If you can't do it yourself, you can turn to professionals. It will be more expensive, but more reliable.