To maintain a normal water-soil "microclimate" in a suburban area, you need to install a drainage system. Moreover, it is advisable to make a hidden option. Then the groundwater will freely leave the site, thereby ensuring the safety of the foundation of the house, the healthy growth of cultivated plants. In order for the communication to work properly, it is important to take care of the correct slope of the drainage pipe by 1 meter in accordance with SNiP.
Conditions for creating a drainage system
The need for a groundwater drainage system arises when the groundwater level on the site in the spring rises to the level of 1.3-1.5 meters. This situation threatens with swampy lands, flooding of basements, basements.
The main elements of the hidden drainage system are tubular perforated drains, which are additionally wrapped with geotextiles. Sand and crushed stone sprinkles are also important. They play the role of a kind of filter that prevents the ingress of earth into the sleeves of the line.
According to SNiP standards, any drainage circuit must be equipped with inspection wells. This allows you to control the operation of the system at any part of it.
Recommended slope levels
In addition to the diameter of the drainage pipes, an important parameter in the construction of the system is the level of the slope of the drains. As a rule, these norms are regulated by SNiP with an indication of the minimum permissible values. In this case, it is important to take into account the lowest groundwater flow rate along the branches. According to the regulations of the official document, for a smaller section of drains, a larger angle of inclination is provided.
Minimum slopes for drainage pipes of different diameters according to SNiP:
- open (external) trays and ditches for water drainage - 3 mm per square meter;
- freestanding gutters - 0.005 mm per square meter;
- cobblestone or asphalted blind area with trays - 3 mm per square meter;
- device of paving stones or crushed stone with open-type gutters - 4 mm per square meter;
- pipes with a cross section of 40-50 mm - 3 cm / l.m .;
- sleeves with a diameter of 85 mm - 2 cm / l.m .;
- drains 100 mm - 1-1.5 cm per square meter;
- 150 mm - 8 mm per square meter;
- 200 mm - 7 mm per r.m.
Always take into account the type of soil on the site. In sandy, the level of filling the circuit with water and its movement will be faster than in clay. Therefore, the slope must be made slightly larger than with denser soil layers.
What threatens the wrong bias
It is important to correctly calculate what angle of inclination the drainage pipe should have. Failure to comply with the recommended standards may lead to emergency situations.
- With a small slope, a gravity drainage system will lead to stagnant water in the sleeves. The debris present in it in the form of small grains of sand will be deposited. Sooner or later, their number will lead to the formation of a blockage in the pipe. We'll have to dig out a section of the system and carry out repair work.
- If the slope is insufficient, groundwater will fill the entire drainage gap, but will not be able to go in the desired direction. As a result, the GWL will remain at the same level, and the installation of the drainage system will be simply meaningless. The site will remain swampy.
- If the recommended slope is increased, the water flow rate will be too high. This threatens to rupture drains over time in some area under the influence of pressure.Either the water at a high speed will go to the discharge point, and heavier impurities (grains of sand, clay particles) will settle at the bottom of the circuit. Sooner or later, this will lead to a blockage.
With insufficient slope of drainage pipes and stagnation of groundwater, constant soil erosion will occur. The natural strength of the upper layers of the earth on the site will decrease.
How to calculate the correct tilt angle
To carry out the installation of the drainage system on the site and at the same time calculate the optimal angle of inclination, you need to take into account the following parameters:
- Drains section. It directly depends on the type of drained soil. The looser it is, the larger the contour diameter should be.
- Type of drains used: with or without geotextile. The first option is optimal for loose soils with an abundance of sand. For coarse-grained soils, it is allowed not to use geotextiles.
- The depth of the contour.
- The relief of the site: the differences in its heights.
- Groundwater level on the ground - it is advisable to carry out preliminary hydrogeological surveys.
- Soil type - information is taken from the table “Classification of soil types.
To correctly determine the slope of the entire line from the top point of the first drain to the point of water discharge, you need to do the following:
- From the highest point of the first pipe to the final receiver of groundwater, the total length of the drainage circuit is measured. In total, it turns out, for example, 20 m.
- Measure a straight segment from the top of the system to the bottom. It turns out, for example, 10 m.
- Both numerical values must be added: 10 + 20 = 30 m.
- To calculate the difference in height between the upper and lower points, a value of 1% of the total is taken. In this case, it is 0.3 m (30x1% = 0.3). Thus, the master must lay the drainage system on the site so that the difference between the upper part of the communication and the lower one is 30 cm. This will be considered the correct slope.
This communication will function smoothly.
