An external sewage system is required in private and multi-storey buildings, but in the first case it is easier to lay it yourself. It is important to pay attention to the characteristics of the pipes and the basic rules for installing the system.
Actual requirements for the laying of an external pipeline
The entire sewerage system of a private house is divided into internal and external. Pipes laid in the building collect wastewater from household appliances, sinks, toilets and bathtubs, supplying them to a common riser. A single pipe is led out into the street, where the outer part of the sewer begins. It includes a pipeline through which liquid wastes are sent to the treatment plant.
You can get rid of impurities in the following ways:
- Connecting an external sewerage system to a centralized system. It is enough to lay a pipeline and equip a well.
- Arrangement of an individual cesspool or septic tank (the most important structural element). In this case, you will need to install a local cleaning system.
According to the requirements of sanitary standards, wastewater must be disposed of in such a way as not to pollute the aquifers of the adjacent territory.
Individual ways of cleansing impurities:
- Cesspool. The inconvenience of the solution is compensated for by its cheapness.
- Septic tank - to clean it, you will need to regularly call a sewer.
- Double chamber tank with double cleaning. In the first tank, heavy fractions settle, in the second, additional filtration is carried out, after which the water is discharged into the ground.
- Biological treatment station. Sewage is decomposed by certain microorganisms.
If funds are limited, it is worth choosing a cesspool. With a sufficient budget, a biological treatment plant can be installed.
Before laying the external sewerage, prepare a project that meets the requirements of the codes of practice "Sewerage. External networks ... "(SP 32.13330.2012) and" Single-family residential houses ... "(SP 55.13330.2011). These documents replaced the SNiPs of the same name.
- relief of the local area;
- soil characteristics;
- the number of people living in the cottage;
- general climatic conditions;
- distance to sources of clean water;
- the possibility of connecting to the central sewerage system or calling the sewers.
The sewerage system of a private house operates on a gravity basis. Installation of horizontal sections of the pipeline outside the cottage must be carried out with a slope towards the cleaning system. Avoid tilting too much as solids can form at the entrance to the sump. The optimal angle is selected based on the diameter of the pipes:
- D500 mm - the slope should be 30 mm / running meter.
- D1000-1100 mm - 20 mm / m.
- D1600 mm - 8 mm / m.
Errors in creating an external sewage system increase the risk of regular blockages and poisoning of drinking water sources.
Choice of pipes
Cast iron and asbestos cement are heavy, so it is difficult to lay sewage from such pipes on your own. Polyvinyl chloride, a lightweight, convenient and non-toxic material, is very popular when installing an internal drainage system. However, it is not suitable for the outer part - during severe frosts, the risk of cracking the walls increases.
Polypropylene has the following advantages:
- high resistance to low temperatures;
- chemical inertness;
- low weight of products;
- high mechanical strength;
- lack of corrosion;
- long service life;
- low roughness coefficient.
Polyethylene pipes have a significant advantage - they do not burst even with complete freezing. In addition, these products can withstand sewage temperatures up to 95 degrees and are resistant to aggressive chemicals. The service life of polyethylene products is 40 years or more.
Features of the choice of pipes:
- Polypropylene products should be smooth.
- When choosing polyethylene, it is better to purchase corrugated elements. They are better suited for the construction of an underground highway, since they cope well with high mechanical pressure (for example, if they are laid under an asphalt track).
Plastic products are easier to install, but when choosing them, you need to take into account the operating conditions: the depth of the location, the presence of a passage area above the pipes.
Design and preparatory work
A project is an obligatory document required for a sewage system. It should be included in the plan of the house as a whole. If you have a ready-made version, adapted to a specific climatic zone, you can prepare tools, look for materials and get to work. If the project is created independently, it is better to show the result of planning to a specialist.
The device of external sewerage networks is carried out in accordance with the documentation that takes into account:
- the level of soil freezing;
- depth of groundwater - the installation site is chosen so that wastewater cannot enter the aquifers, fill the foundation or basement of the house;
- the possibility of access to the sewage treatment plant;
- septic tank volume - must correspond to the number of permanent residents, for 3 people a tank of 4 m3 is enough;
- location of inspection wells.
When creating an external drainage network, it is important to consider the location of the storm sewer.
Installation features
External sewerage network laying technology:
- Preparation of the pit. The trench is dug with the calculation of such a position of the pipes, in which they would be 50 cm below the level of freezing of the soil (for the southern regions - 1.5-2 m, for the northern regions 3-3.5 m). For pipes with a diameter of 110 mm, dig a trench 60 cm wide. The bottom of the ditch must be leveled and tamped. A layer of sand with a height of 10 cm is formed from above.At the place where the pipe enters the septic tank or collector, an area 2 m wide and 1 m long is created.
- Pipe laying. After completing the digging of the pit, pipes are laid along its length without cutting. Tees, crosses, revision fit into the required points. The assembly starts from a local septic tank. Before joining the pipe ends, lubricate with silicone sealant. If you need to create turns, it is better to use 45 degree corners. In these places, it is worth installing a well with a revision.
- Warming. When installing an external sewage system, sometimes it is necessary to additionally protect the pipes from frost. If a trench is dug of sufficient depth, this is not necessary, but in regions with cold winters, it is worth playing it safe. Polystyrene, polyurethane foam, heat-insulating paint, basalt fiber or glass wool are used as insulation material.
- Backfilling. At this stage, it is imperative to use the soil that was selected from the trench. To prevent damage to the pipe, stones, hard clods and debris must be removed from the ground. It is better to use sand, at least to the level of the upper edge of the product. To compensate for the shrinkage of the earth above the trench, you need to make a small tubercle. If electrical equipment is installed in the sewage treatment plant, a screened cable must be laid in the ditch before backfilling.
You can complete each of these steps yourself. It is better to consult a specialist before work.
Common mistakes
It is possible to install the external sewerage system with high quality and in a short time while avoiding the following mistakes:
- Savings on materials. The difference in cost with cheap counterparts may be less than repairing the system.
- Installation of pipes for external sewerage in a short time. Sections of the pipeline must be carefully measured and carefully cut. The angles of inclination must be created exactly according to the project.
- Insufficient placement of drainage pipes. If they become clogged or have a low flow rate, liquid stagnation will occur.
Prices per meter of work on laying an external sewage system start from 270 rubles (when installing non-pressure PVC systems with a diameter of 110 mm). With a pipe size of 500 mm, prices increase to 800 rubles.
