A wastewater system is an integral part of any home. For it to function correctly, you need to properly equip it, that is, choose the right angle at which it will be laid. Many are asking quite a legitimate question whether, according to SNiP, will the sewer slope of 1 meter be sufficient or should it be done more (or maybe less). Let's figure it out.
On a note! Even if you equip the sewage system at the right angle, this will not guarantee the normal and durable operation of the sewage system. Since there are still a number of points that must be taken into account during its installation: location (piping layout indoors or outdoors), configuration, diameter and material of pipes.
What is the angle of inclination for?
Why is a well-defined slope of the wastewater system needed? Maybe it’s enough to just lay the pipes and not “bother” about how to make the sewer slope 1 meter - SNiPom recommended values?
The main arguments for arranging sewage at a certain angle:
- Without it, the liquid will begin to stagnate in the pipes (which is not good).
- Sewerage should function without any malfunction, despite the inability to predict the consistency and nature of the sewage.
- The main purpose of arranging the slope is the desire to minimize, to a minimum, the possibility of settling of solid fractions (or sludge) on the walls of the laid pipeline.
- Ensure silent operation of the system, while avoiding the reverse flow of wastewater and eliminating unpleasant odors directly in the room.
Too small slope or too large - which is better?
The most important thing is to determine the minimum slope, since with too little wastewater will not flow out completely. As a result, you can’t avoid clogging the pipes and all the ensuing consequences.
Good. Maybe then to make a large slope and be sure that everything is fine with the fluid flowing out and not to calculate the minimum angle so that the slope of the sewer pipe by 1 meter - SNiPom recommended values - were observed? No, bad again. This is not an option. The fact is that if there is too much slope in the pipe, large fractions will absolutely be guaranteed to accumulate and contribute to the formation of blockage. The fact is that with a very large slope, the liquid flows quickly, and to remove the solid elements, more time is needed (and there is already nothing to wash them off). As a result, the pipe is clogged, you are in a panic.
It turns out that it is necessary to find a “middle ground”, namely, to determine the minimum angle of inclination of the sewage system so that it functions well. If the design and installation of the sewer system is carried out strictly according to the norms of such a document as “Building Norms and Rules”, that is, the sewer slope of 1 meter (SNiPom recommended values) is maintained, this will significantly increase the service life of the system that discharges waste water, and, of course , the quality of her work.
We calculate the minimum angle of inclination
To determine the minimum angle of inclination, it is necessary to make mathematical calculations using a certain formula. Here it is - V√H⁄D≥K: V is the rate of fluid discharge (optimally, it is 0.7 m / s); H is the level of wastewater (that is, it determines the degree of fullness of the pipeline and should be about 50-60%); D is the diameter of the pipeline; K is the slope coefficient of the pipeline (optimally, it should vary in the range from 0.5 to 0.7; that is, the closer to 1, the better).
Important! The degree of filling of the pipeline should not be less than 1/3.
Pipe Slope Ratio
This indicator can be determined in two ways:
- Calculate yourself by the formula - H / D.
- Refer to reference material.
On a note! The value of this coefficient, indicated in the reference book, is directly dependent on the material from which the pipes are made: 0.5 - for glass and plastic; 0.6 - for materials such as cast iron, asbestos cement or steel. Also, do not forget about the degree of roughness of the inner surface of the pipe, which negatively affects K.
From practice it is known that approximately a slope of 20 mm (per 1 meter of sewage) will be enough.
Pipe diameter
If there is no desire to make any calculations, you can do without them: it is possible to determine the necessary slope of the sewer system depending on the diameter of the pipes. Practical, convenient and fast.
Naturally, all this can be done if the diameter is selected so that the conditions for filling the pipeline (50-60%) and the velocity of the fluid (0.7 m / s) are met. Otherwise, nothing will work.
As a rule, the calculation simply comes down to choosing a certain diameter (200, 150 (160), 100 (110), 80, 50 mm) and refining the angle of inclination, respectively.
Important! Do not forget the margin of error.
In SNiP, depending on the diameter, the values of the minimum and maximum slopes are presented. If you multiply these values by 100, you will get these figures in centimeters.
Important! All these values can be used to equip slopes exclusively on level areas (that is, without connecting to the outlet pipes, siphons and other systems).
Location of wastewater system
There are two wastewater systems:
- Inner. This is a set of pipelines that ensure the diversion of existing effluents from plumbing devices and their withdrawal from the building. Most often, owners of private houses are engaged in the arrangement of such a system on their own. Fortunately, a wide range of various plastic elements is presented on the construction market.
- An external sewage system ensures the delivery of waste fluid from the building to the septic tank (storage and cleaning complex).
Internal piping
In addition to the slope of the internal sewage system by 1 meter (SNiPom recommended values), it is necessary to adhere to the following recommendations:
- We use pipes with a diameter of 100, 80, 50 or 40 mm (moreover, a diameter of 100 mm is used to connect general-purpose areas, that is, in places where the pipelines converge).
- We make the most optimal slope values for pipes of these diameters, namely: 0.015, 0.2, 0.03 and 0.035, respectively.
- If, according to the technological process, it is necessary to use adapters (for example, when switching from a larger to a smaller one), we do this in such a way that the evenness of the lower part of the channel is not disturbed. Otherwise, the continuity of the flow of water may be impaired.
- We provide the necessary slope by means of fixing systems or by sloping the box into which we install the sewer system.
On a note! Be sure to observe the necessary bias when arranging the pipeline from the device to the sewer system. Moreover, a turn to a similar system is equipped with a tee or knee (the slope should be about 70 degrees).
- We do not allow pipe bends at right angles to the pipes. We use exclusively bends (at 45 degrees and only).
On a note! If the pipe is of insignificant length, then deviation from a certain slope is quite acceptable.
External piping
In addition to the slope of the external sewage system by 1 meter (SNiPom recommended values), it is necessary to adhere to the following recommendations:
- Depending on the soil and climatic conditions, the depth of the trench can vary between 100-200 cm.
- For the proper implementation of the necessary bias, do not forget to take into account the ever-increasing recess. To do this, we initially do the depth deeper than 25 centimeters, so that it is convenient to equip the sand support under the system.
- We carry out the pipeline laying line at a depth below the freezing level (350 mm). When laying above the level, you should think about enhanced thermal insulation.
- The diameter of the pipes used is 110-200 mm. Moreover, the minimum slope is: 200 mm - 7 mm, 160 mm - 8 mm. But according to SNiP, the sewage slope of 1 meter (110 mm of pipe in diameter) is about 20 mm.
Remember! If you want the slope to be the most effective, adhere to the rule: the slope is not more than 150 mm (based on each linear meter).
- Pipes are located on the same level, without changing the slope along the entire length.
Remember! It is unacceptable to combine pipes of various diameters. Also, one should not allow level differences in the gasket. If such a need arises, then the equipment of the inspection well is necessary.
Storm sewer
The function of storm sewers is the removal of melt and rain streams (to avoid wetlands and to maintain the foundation of the building).
In addition to the slope of storm sewers by 1 meter (SNiPom of the recommended values), other factors must be observed, namely: the type of drainage and the diameter of the pipe.
On a note! The minimum slope for the removal of melt and rainwater should be as follows: 7 mm (for pipes with a diameter of 200 mm) and 8 mm (for 150 mm).
In addition, it is necessary to take into account other points: the characteristic features of local soil, the average amount of rainfall in the region of residence, and the volume of wastewater.
Pipe configuration
Is the condition of the sewer slope of 1 meter (SNiPom recommended values) the only one for the high-quality operation of the sewage system? Not. There is one more important condition, without which clogging is inevitable. This is the configuration of the laid pipeline. After all, if it is too “sophisticated” and has a large number of bends, then the wastewater will not be able to quickly drain (without stopping inside the pipes) into the collector, and then straight to the treatment plant. In this case, no sewage slope of 1 meter (SNiPom recommended values) will not save the situation.
Pipe material
Sewer pipes can be:
- plastic;
- cast iron;
- concrete;
- asbestos-cement;
- ceramic.
Most often, plastic pipes are used for the construction of the internal sewer system, and asbestos-cement, cast-iron or corrugated pipes are used for the external.
Finally
After reading the article, it becomes clear that the maximum sewage slope of 1 meter (recommended by SNiPom) will not solve the problem, but will aggravate it. The only correct solution is to determine the minimum angle of inclination. Well, of course, do not forget about the configuration and material of the pipeline. And you will be happy.