Well, the last article in the topic of calculating the size of a septic tank is about how to calculate the volume of a septic tank.

At the same time, we will touch on the calculation of the size of the drain pit - maybe it will come in handy for someone.

And since this article is the last one, we will draw final conclusions about the choice of sizes of septic tanks.

The number of chambers and the design of the septic tank

A septic tank is a container with a number of chambers from one to three. The chambers are interconnected by means of pipes to enable the wastewater to pass from one chamber to another and so on to the last filtering chamber:

Water from the extreme chamber can go into the soil through pipes or directly through unsealed walls and bottom ... although this is not welcome, it is necessary to clean these drains, which, however, I already wrote about in the very first article about septic tanks. Then why am I repeating here about the design and what does the size of the septic tank have to do with it, you ask? To refresh our memory - this will come in handy, starting with the next line ...

How to calculate the volume of a septic tank?

The volume of a septic tank does not mean the entire volume of the tank, but only its working volume.

What is the working volume of a septic tank?

Let's look at the diagram (clickable):

The outlet from the septic tank is 3-5 centimeters below the inlet. Therefore, the volume of the septic tank is considered only working - one that can be filled with drains, from the outlet level to the bottom.

Calculation of the volume of a septic tank by the number of drains

Well, now the actual calculation of the volume of the septic tank.

To calculate the volume of a septic tank, you need to take into account the average daily volume of effluents. Because the water should not just flow through the septic tank without stopping, but should be inside for some time so that the solid particles have time to settle. In addition, the processes of decomposition of these particles also require time. Therefore, wastewater in the septic tank must be at least two days. But ideally - up to ten days! I believe it is clear: the longer the drains stay inside the septic tank, the better they will be cleaned (settle).

From these considerations, we calculate the volume of the septic tank.

In SNiP it is written: “the full estimated volume of the septic tank should be taken: with a wastewater flow rate of up to 5 m3 / day. - at least 3-fold daily inflow, at a flow rate of more than 5 m3/day. - not less than 2.5 times” (p. 6. 79.).

Again. Let's say we figured that the volume of effluent from our house would be about 5 m3 per day. This means that the minimum volume of our septic tank should be 15 m3. More is possible, less is not. With a volume of wastewater greater than 5 m3, we multiply our “estimated” value by 2.5 and we also get a value, less than which the volume of the septic tank should not be made, but more - as much as you like.

By the way, with such calculations, at least once a year, the septic tank will need to be pumped out.

The volume of the septic tank and the number of chambers

Apart from what has been said. Septic tanks can be made with one, two or three chambers.

The volume of these chambers is also regulated by SNiP:

“Depending on the flow of wastewater, the following should be taken:

single-chamber septic tanks - with a wastewater flow rate of up to 1 m3 / day,

two-chamber - up to 10 m3 / day,

three-chamber - over 10 m3 / day.

The volume of the first chamber should be taken: in two-chamber septic tanks - 0.75, in three-chamber - 0.5 of the estimated volume of wastewater. In this case, the volume of the second and third chambers should be taken at 0.25 of the calculated volume. In septic tanks made of concrete rings, all chambers should be taken of equal volume.

In my opinion, everything in SNiP is written quite transparently, there is nothing to comment on.

Calculation of the volume of a septic tank according to the formula

The volume of the septic tank \u003d (The number of people living in the house x The rate of water consumption per day for 1 person x The number of days for which the septic tank cleans the water) / 1000

So, the conditions of the task:

A family of 4 lives in the house,

The daily rate of water consumption per person is 200 liters,

Drains in the septic tank must be settled for at least 2 days.

Substitute the data in the formula and calculate:

The volume of the septic tank = (4 x 200 x 2) / 1000 = 1.6 m3.

I remind you: we considered the WORKING CAPACITY of the septic tank, and not the full volume of the tank.

But do not rush to grab a shovel and dig, please read the article, there is something else that needs to be taken into account when calculating the volume of a septic tank. Namely: the volume of the sewer tank.

How to calculate the size of the drain pit?

The depth of the drain pit can be determined in the same way as the depth of the septic tank. But, since there are no hydraulic requirements here, the shape of the drain pit no longer matters much (let me remind you that water flows through the septic tank, but it just "waits" in the drain pit). How does not matter the ratio of the length and width of the pit.

The volume here is also calculated from the average daily water consumption.

You can apply this formula:

Vpits - the volume of the drain pit,

Ndays - the estimated number of days after which the pit is pumped out (for some reason it is recommended to do this at least twice a month, that is, every 15 days, I don’t know why, maybe so that the sewers do not wean themselves from work? :)),

N people - the number of people permanently living in the house,

V1 - the estimated volume of water per day per person (it is believed that this is ~ 150 l).

For example, if a family of 4 people permanently lives in a house, then:

Vpits = 15 * 4 * 150 = 9000 liters = 9 m3

Arrangement of an absorbing drain pit allows wastewater to be discharged directly into the soil. This is possible with small (in my opinion, less than one cubic meter) volumes, since it is not capable of causing significant harm to the environment.

The volume of the septic tank and the volume of sewage tanks

In the examples of calculations given above, of course, the values are averaged.

It is better to increase the time for settling wastewater in septic tanks.

The volume of the septic tank and the drain pit can be adjusted to the volume of the tank of the sewage machine, which will pump out sewage. It is not recommended to make a septic tank less than 3 m3 (the tank of a sewage truck has approximately the same volume, a little more: 3.2 cubic meters). If the septic tank is significantly smaller, then it turns out that you are paying for a full car, but in fact it will take out only a part of its possible volume.

There are cars with a five-cube tank; if they are in your area, then you can orient the volume of the septic tank to them, check this where you live.

General conclusion about the calculation of the size of septic tanks

So, in order to determine the dimensions of the septic tank, you need to correlate the following: required working depth of the septic tank, surface area (length x width), minimum and maximum allowable dimensions, as well as the capabilities of the sewage machine (unless, of course, the septic tank will be pumped out by it). And then we move on to the choice of materials; read about the pros and cons of each material and the construction technology of them in the following articles.

Before installing a septic tank, a calculation is carried out to ensure its trouble-free operation. It is required to have quite a lot of data that will allow you to calculate the volume and size of the treatment plant. Professionals use complex formulas, special tables that are difficult for a non-specialist to understand. Usually a simplified approach based on theoretical knowledge and practical experience is used. It is on this option that the article is focused to help calculate the volume of the septic tank.

When making calculations for a septic tank, the first thing to take into account is the volume of drains that it must take per day. That's where the dimensions come from. But not everything is so simple: there are many nuances in the calculations. For example, three people constantly live in the house, and 2 more people come to visit them every weekend. They need to be taken into account somehow, because they also use the sewerage system.

Water consumption in each case is individual: the most accurate calculation will allow you to correctly determine the volume of the septic tank

There are a lot of such subtleties, but in general it all comes down to what you need to know:

on daily water consumption and, accordingly, the volume of wastewater;
building codes;
sanitary rules;
technical capabilities of various types of treatment plants.

With this knowledge, you can correctly calculate the volume of the septic tank.

Daily water consumption

This is a very controversial issue. On the one hand, there are standards adopted long ago, which determine for each person 200 liters of water per day. Naturally, they almost 100% go to stock. But reality is often far from office calculations. Some families consume much less, others more. In private houses where septic tanks are used, water meters, as a rule, do not stand, because the water is from its own well.

Water consumption depends on the size of the family and living conditions

The easiest way is to find out the daily water consumption by the meter, and when it is not there, use the table and formula.

Using the table, make real calculations. Suppose there are 4 people in a family, each of whom uses a shower, bidet, toilet every day. There are 96 liters per person, but they visit the toilet more than once, many take a shower 2 times a day, or even more. Plus, laundry, washing dishes, there will definitely be a bath lover in the family.

It is impossible to say exactly how much water one person and the whole family consumes per day. This can only be calculated by family members. Too different today people have opportunities and needs.

Building codes and sanitary rules

The SNiP states that the volume of the septic tank should ensure the reception of wastewater in three days. Based on their water consumption standards for one person - 200 liters, the septic tank should hold 600 liters. This is for one family member, if there are three of them, then 1.8 m 3, for five - 3.0 m 3.

That's not all. Sanitary standards are more stringent. They indicate that the discharge of treated effluents is allowed 2 weeks after entering the reservoir. During this time, the bacteria will process the organic matter, and the effluent can be dumped. That is, if a family of three per day sends 0.6 m 3 of wastewater to the septic tank, then it should hold 14 times more. This is equal to 8.4 m 3. Rather big, in practice, no one uses this for three people.

The volume of the septic tank includes capacity, which is measured from the bottom to the pipe. In addition, it is taken into account that a precipitate forms in the first tank, which occupies 20% of its volume. With this in mind, according to the standards of SNiP, a septic tank for three people should hold 2.16 m 3, and for five - 3.6 m 3. According to sanitary rules, respectively, 14 times more.

Regarding the norms of SNiP, it can also be said that in some families the daily consumption can be 100 liters. Then for four people there will be enough septic tank for 1.5 m 3. But it should be understood that the sanitary and epidemiological service may prohibit the use of such an installation - they have their own rules.

Is it worth saving on the volume of a septic tank?

A septic tank of a smaller capacity, purchased or home-made, will cost less. The benefit here is only at first glance. If you look deeper, it turns out that you often have to discharge wastewater from a small-volume septic tank or take it out with a sewer machine. Organics, among which there are many sparingly soluble substances, are not completely processed by bacteria.

If poorly purified water is used for irrigation, it will destroy plants and your health. If heading for a drainage field, one should be prepared for the fact that the filters will soon become clogged with difficult-to-decompose fats. And this is a system change. Saving on the volume of a septic tank turns into a lot of problems.

Calculation of volume according to the formula

Engineers and designers have developed tables and formulas that calculate the volume of a septic tank. The water consumption table above will come in handy.

Important! It is taken into account that the minimum depth of the septic tank is 1.3 m, and it is not less than 1 m in length and width.

The most accurate volume values are obtained using the formula:

The effluent temperature has different values depending on the equipment from which they flow. For calculations, average values are used: in winter - + 10 ° С, in summer - + 20 ° С.

The exact data is given in the following table:

For calculations using it, the formula W \u003d K × Q is used. Here K is the daily runoff.

Calculation examples

At home, a simplified formula is used to determine the capacity of a septic tank. With such calculations, it is important to correctly calculate how much water is actually consumed by the family.

The calculation of the volume of a septic tank begins with determining the amount of water consumed

Calculation example for a family of four:

SNiP defines the minimum water consumption per person per day of 150 liters. They add a washing machine and a dishwasher - these are 70 and 15 liters, in total 235 liters are obtained.
Now they calculate how much water is consumed per day by a family of 4 people: 235 × 4 = 940 liters.
Drains must settle for at least 3 days. To do this, you need a septic tank volume of 940 × 3 = 2820 l or 2.82 m 3.
The volume of sludge is taken into account - at least 20%. 2.82 + 20% \u003d 3.384 m 3. With the above daily water consumption of 235 liters, four people will need a 3.5 m 3 septic tank.

If we carry out calculations for the maximum daily consumption, which is defined by SNiP as 370 l, then a treatment plant is needed to serve 4 people: 370 × 4 × 3 + 20% = 5328 l or 5.328 m 3. Round up to the nearest higher value and get 5.5 m 3 .

To calculate the minimum allowable volume, the 20% occupied by sludge is ignored. This is the maximum rate, a larger decrease threatens to flood the septic tank, poison the soil, and possible fines from state bodies that have every right to do so.

A.V.Bobrov, chief engineer of "Septic installation"

If guests often come, the daily consumption is increased by 200 liters and appropriate calculations are made. A preliminary adjustment is also required if an addition is expected in the family. It is better to have a reserve of volume than to worry that all the drains will not enter the septic tank.

Number of chambers in a septic tank

According to the SNiP standards, when no more than 1 m 3 of wastewater enters the septic tank per day, the treatment plant can be single-chamber. With a wastewater volume of 1–10 m 3 - two-section. If the drains are more than 10 m 3 - from three compartments.

If the septic tank is not used in the country, but in a house where people constantly live, the best option is a three-chamber septic tank. There are several reasons for this:

In a single-section septic tank, fresh receipts are constantly added to drains that have not had time to be fully cleaned. The quality of cleaning is significantly reduced, dirty water enters the soil, which threatens the environmental safety of the site.
Domestic sewage contains a lot of sparingly soluble fatty compounds, which take a long time to be processed by bacteria. Fats do not have time to break down, other layers settle on top of them.
If the septic tank is in the form of a drainage well, its bottom quickly loses its filtering ability. It clogs up, the water does not go away, you have to call for sewers to clean it.

Cleaning is effective when the processes are divided into mechanical and biological. Then, in the first chamber, solid particles fall to the bottom, and in the second and subsequent chambers, the effluents are processed by bacteria. Here mechanical post-treatment takes place to a small extent. In this case, the last chamber can be used as a drainage well, from where the effluents go into the ground for additional filtration.

Advice! Experts believe that the minimum number of cameras in a septic tank is two, and the optimal number is three. At the same time, different sizes of sections are required: the first one accounts for 50% of the total volume, the next 2 occupy 25% each.

The division of the septic tank into sections of unequal volume is clearly seen in the example of an industrial treatment plant: the first chamber occupies half of the entire capacity

Questions and answers

Question 1. How is the required capacity of a septic tank determined - for the entire volume, or only for the drive?

When calculating, the volume of the first chamber is important, which, in terms of capacity, is able to accept three-day drains.

Question 2. If you put a larger septic tank, will it protect against volley discharge, will the quality of cleaning improve?

Drains will come out much cleaner, underground filtration will work much longer. An excessive increase in volume is not recommended - the effect is too small, and the costs are high. A two- or three-fold increase will allow you to forget about sewage almost forever.

Septic tank calculator.

Septic tank selection calculator- a useful feature for anyone who is going to install an autonomous wastewater treatment system in their summer cottage or in a private house. In order to choose the right device for such a device, it is necessary to take into account several parameters: from the number of people who live in the building to the type of soil. With the help of a calculator, you can not carry out long calculations, but enter the necessary parameters and wait for the results to be generated.

Septic tank selection calculator

Main settings:

Number of residents

Pipe depth

Discharge of water from a septic tank

Accommodation

Soil type

High ground level. waters

Plumbing:

0 1 2 3 4 5

Pick up

How to use the septic tank selection calculator?

Septic tank selection calculator will prompt the user:

Enter the number of residents in the served area;

Choose the type of residence - permanent, seasonal or weekend;

Specify the depth of the pipe in centimeters;

Determine the type of soil in which the pipe will lie;

Choose where the water from the septic tank will be discharged: onto the ground, into a well / ditch;

Indicate if a high groundwater level is observed.

After these data are entered, you will need to indicate the number of plumbing products and household appliances that will be used in the house on a regular basis. These include:

Toilet bowls;

Bidet;

Shower;

Bath;

Sink;

Jacuzzi;

Washing machine;

Dishwasher.

Opposite each product / device, you must put the desired number. After that, it remains to click on the "Select" button and wait until the system selects the systems suitable for a particular case. As a rule, it will take no more than a few seconds to generate the results.

The system will calculate the volume of water consumption per day on average, and also indicate the maximum volume of a single discharge of liquid. Below are the models that are best suited for the specified parameters. In order for the calculation results to be as close as possible to reality, it is recommended to choose the most accurate parameters. Therefore, it will be useful before activating septic tank calculator, take an interest in the features of the soil and decide in advance where the treated water will go.

Why do we need accurate calculations using a septic tank selection calculator?

Autonomous treatment facilities can greatly facilitate living in a country house or in a summer cottage, where for some reason it is impossible to insert into the central sewer. A septic tank will allow you to process used water and drain it to the ground without harming the environment, or reuse the liquid for household needs.

With the help of autonomous sewage, you can significantly increase the comfort of using plumbing and household appliances and not think about how to get rid of drains and where to get water for irrigation - just organize a channel where the waste liquid will drain. However, there is one "but".

For optimal selection, it will be necessary to carry out complex calculations that take into account all the above parameters. It will be difficult for beginners in this matter to cope with such a task, and an error in the calculations can lead to the fact that the wrong septic tank is chosen. This is fraught with consequences.

If the performance of the cleaning system is too low for a particular house, the number of residents and the number of household appliances and plumbing, this will lead to the fact that you will have to limit yourself in using water. Such an exit brings certain inconvenience to everyone who lives in the house.

High performance where there is no need for it will not lead to anything good either. Of course, you won’t have to save on laundry and taking a bath. However, we must remember: the higher the performance of a septic tank, the greater its cost. If you choose a cleaning system that, for example, can serve ten people, and in fact three people live in the house, it turns out that users are throwing money away.

In addition, it should be remembered that septic tank calculator takes into account not only the number of residents and the number of household appliances and plumbing fixtures, but also the type of residence, as well as the type of soil and the possible level of the pipes. After all the necessary parameters are included in a special table, he selects the most optimal options for all the specified characteristics. Therefore, in order not to delve into various technical issues, not to waste time, and not to worry about a potential error, you should use the possibility of automatic calculation with the selection of the most suitable devices.

Advantages of using a septic tank selection calculator.

Apart from septic tank calculator, you can also use the services of the relevant organizations that will make all the necessary calculations, take into account the wishes of the homeowner and tell you what parameters he should rely on when choosing a system, as well as which models should be paid attention to. Specialists will be interested in the same parameters as the calculator, after which, after a certain period of time, they will give the results of the calculations. Of course, not for free.

Septic tank selection calculator, presented on the site of the Stroy Project organization, will do the same. However, it will take much less time, and besides, all calculations using this function are free of charge. The calculator does not have to go to the site to evaluate everything with his own eyes. In this case, you can observe tangible savings in time and money for the customer.

You can use the calculator at any time of the day or night, since the site of the Stroy Project organization is freely available around the clock. And, after the user has received the calculation results, he can get acquainted with the proposed models, their characteristics, parameters and technical features. After studying all the options offered, it remains only to make your choice, or seek help from the company's employees who will help him make the right choice.

Communications of a country house have a local system, which differs significantly in its design from a centralized sewerage system. Autonomous functioning occurs according to a certain cycle. A reservoir is involved in the process of processing wastewater, many household factors depend on its volume, the lack of m³ of the used septic tank will lead to various undesirable consequences, including the need for strict control over the amount of liquid consumed. Buying a huge capacity without calculations is just wasted money.

To make the correct calculation, to avoid unnecessary expenses, you can understand the whole system as a whole.

Factory septic system

A septic tank is a special tank, made independently or purchased from a manufacturer, in which wastewater is accumulated, organic compounds are gradually processed, and the purified liquid is disposed of.

The working process of the septic tank begins from the moment the contaminated water enters the tank into the first compartment, called the sump - phase 1. The liquid settles, the effluents are divided into fractions, heavy and large elements settle to the bottom, the rest of the liquid passes to the 2nd cleaning phase in the second compartment, after clarified water goes to compartment number 3.

The division into fractions occurs at all stages, bringing water to 96% of the primary state. Despite the high level of purification, such water can be used for technical needs, in the absence of a great need for technical water, the liquid is disposed of in the ground, where it reaches complete cleaning with soil.

Processing is carried out in the following ways:

aerobic;
anaerobic;
mechanical method.

The aerobic and anaerobic cleaning method refers to the bacterial one, it is distinguished by the ability to conduct the vital activity of microorganisms in the absence of air in the system. Equipped with an air duct system, aerobic bacteria can be used. The best option, according to practitioners, the use of both types of cleaning products gives the maximum effect.

The mechanical method is used separately, as a post-treatment facility.

It is erroneously believed that efficiency depends on volume. The result of processing depends on the number of stages passing by wastewater.

How many chambers should be in the septic tank to obtain the desired result?

It is necessary to independently determine in what way the disposal of the purified liquid will take place, since there are state sanitary and hygienic, environmental standards in which the degree of purification of the utilized waters into the soil is clearly specified. It is necessary to achieve maximum purification in order to avoid contamination of drinking water sources.

SNiP 2.04.03.85 contains information for each type of building, houses of permanent and temporary residence are very different in terms of water consumption.

Single-chamber septic tanks have the lowest degree of purification, constant mixing of new drains. Utilization of such waters into the ground threatens an ecological disaster on the site.

Two-chamber septic tanks, an average degree of purification, up to 55%, which also makes it impossible to freely dispose of the liquid into the soil. The light suspensions in it can significantly harm, it is necessary to build additional fields, wells for the purification of water leaving the septic tank.

Three and four chamber septic tanks have a degree of purification from 70 to 96%. The pumping of wastewater from one section to another occurs through pipes, the upper, cleanest layers of the waters located in the section move. The percentage depends on the auxiliary biological material used. After that, you can carry out post-treatment in a well with a special filtering embankment.

We calculate the required volume of the septic tank

Having decided how exactly the wastewater will be treated in the local sewer system, the question arises of how to correctly calculate the volume so as not to overpay for extra cubic meters.

The formula is rather complicated, especially for those who do not have information. If you doubt your own abilities, it is better to contact professionals.

W = 1460 Qt 0.33 C 1.1 N 0.55 T 0.0283 √ N

where W is the required volume of the septic tank in m³;

t - Time that the sediment is in the section, measured in days;

C - The indicator of the concentration of organic compounds at the outlet in one liter;

N - Daily water intake per person;

T - Temperature of liquefied effluents;

Q - The indicator of the daily norm of effluents in m³.

There is a simpler approach to solving this issue. It takes into account completely different factors. The constant norms established by regulatory enactments are taken as a basis, they are 200 liters of water per day per one living person (permanent stay). To them you need to add the water consumption of all household appliances, multiply by the number of days of the cycle of complete processing of wastewater in the septic tank, for most models this figure does not exceed 3 days and divide by 1000 - a coefficient that converts liters to m³.

The formula looks like this: V= (200*4+250)*3/1000

Calculation of the volume of the factory model for four people

Considering some standards, namely 200 liters per person per day, we get 800 liters x 3 days in total, we get 2.4 m³ - a minimum for a family, but this volume will not be enough, since guests come, there are household appliances. In addition to situations that are difficult to calculate, there are environmental norms and rules, according to which the residence time is 14 days. 800 liters x 14 days, it turns out 11.2 m³. Such a tank is very large, which makes installation impossible in small areas, but with a water consumption of 800 liters in one day, another volume cannot be obtained.

The solution is to reduce the load on the sewer system. Feces will not decrease, but it is possible to reduce the amount of solid fats that are difficult to process by microorganisms. Dispose of the remains of plant products in a compost pit, another place, but do not flush down the toilet.

The productivity of bacteria is reduced by the ingress of chlorine-containing substances into the septic tank, which adversely affect the population and life cycle of microflora.

By limiting the discharge of various types of garbage into the sewer, the volume can be reduced to 400 liters in 24 hours. 400 liters x 14 days = 6.72 m³, which is quite suitable for a family of 4 people. When purchasing a septic tank, it is better to round up the number and make a small margin in case guests arrive.

Any figure obtained from the calculations will be divided by the number of compartments, if the capacity is not a single-chamber model. A three-chamber septic tank divides the total volume in this way: the first compartment is 3.5 m³, compartment numbered 2 and 3 with a volume of 1.75 m³.

Considering all the nuances of operation, the recommendations of the owners, water consumption and the volume of the tank must be planned in such a way that the sewer can take out in one or two full walks, without paying for an empty tank. The sewer tank, on average, is 3.8-5m³.

Calculation of the volume of a septic tank from building materials

Very often they resort to creating a septic tank with their own hands, using reinforced concrete blanks. You can calculate the volume for such a structure in this way. First you need to know the types of rings and their diameter:

meter ring - inner diameter 0.7 m³;
1.5 meter product - 1.57 m³;
2 meters - 2.8 m³.

The drain pipes for the movement of wastewater are located in the upper part, but not as close as possible to the hatch, this arrangement allows you to fill the tank by 80%. To provide an internal volume of 6.72 m³ for four people, you need 6.72 / 0.8 \u003d 8.4 m³ - the figure of the external volume.

Now you need to divide the resulting figure into compartments and elements.

A septic tank of two chambers of 4.2 m³ each - three one-and-a-half reinforced concrete rings 4.71, then the volume of both sections will be 9.42 cubic meters. meters.

A septic tank of three chambers: compartment 1 - 3 pieces of 1.5 meter rings, compartment 2 and 3 - three meter products each - the volume of one section is 2.1 m³. We add up the indicators 4.71 + 2.1 + 2.1 \u003d 8.91 m³, with a load of 80% - the volume of the working space is 7.1 m³.

You can collect any desired volume, remember the installation rules, without which operation will be difficult.

Autonomous sewerage in a private house is a complex system, the device of which is a complex technical task. The sewer equipment market is represented by a variety of options, among which three-sectional septic tanks made of reinforced concrete or plastic are especially popular.

Before buying a septic tank, it is necessary to make an accurate calculation of the usable volume of the future tank. The volume of the septic tank is calculated based on three times the daily water consumption of one person. If the calculations are neglected, then over time the sewage system can fail, which will lead to unpleasant consequences or an environmental problem.

For calculation, you can use the average value of water consumption by one person - 200 liters per day. Or you can follow the meter readings in the house. Using the meter readings, it will be necessary to make an adjustment to the calculated mass of water. This is the so-called reduction factor, which is 0.6-0.8. If the house has a washing machine or dishwasher, then the coefficient will be increasing, which is 1.5-2.

The table shows the approximate volume of the septic tank. The values may change according to the reduction or increase factors.

Number of people	Wastewater consumption, m3/day	septic tank volume, m3
3	0,6	1,5
4	0,8	1,9
5	1,0	2,4
6	1,2	2,9
7	1,4	3,4
8	1,6	3,9
9	1,8	4,4
10	2,0	4,8

According to sanitary standards, sewage must be settled for at least three days, so the estimated volume of a septic tank per person will be 0.6 cubic meters. - 0.2 (200 liters per day) multiplied by 3. Accordingly, for a family of three, the volume of the septic tank will be 1.8 cubic meters. calculation of the volume of a septic tank implies the calculation of the working volume, on which the number of chambers does not depend.

Two-chamber septic tanks will cope with their task as well as a three-chamber tank. If the septic tank has two chambers, then the main volume must be at least 0.75 of the main volume. If the septic tank is three-chamber, the volume of the main chamber must be at least 0.5 of the total, the other two are 0.25 of the main volume.

When choosing equipment, it is important to consider its performance;
Volley discharge of wastewater within two hours;
An important parameter is the depth of the sewer pipe insert, which indicates the depth of the pipe;
It is worth paying attention to the service indicator, which indicates the frequency of removal of sludge from the bottom of the septic tank;
An important indicator when choosing equipment is the depth of sewage treatment. Biological septic tanks guarantee 98% cleaning;
Also, when choosing a septic tank, you should pay attention to the material. A smart choice can make maintenance easier. A septic tank is selected according to what type of soil lies on the site;
An important factor in the convenience of equipment maintenance is the possibility of self-service;
The reliability of equipment depends on its complexity;

Saving on equipment is not always advisable, since sewage contains a huge amount of "heavy" elements that are not always processed by bacteria. In this connection, the septic tank must have a certain reserve of volume so that non-recyclable elements have time to settle to the bottom, which will soon be pumped out by a sewage machine.

Consider the approximate parameters of the norms of water consumption by one person per day:

40 cubic meters - shower (7-10 min);
8 liters - bidet, toilet;
100 liters - bath;
80 liters - washing machine;
15 liters - dishwasher;

An example of calculating the volume for 3 people

To do this, we need the formula for the total volume:

V - working volume (cubic meters);
n is the number of people;
Q - water consumption by one person (l / day);
3 - time of sewage treatment (days);

3*200*3/1000=1.8 cubic meters According to calculations for three people, it will be necessary to install a septic tank with a total volume of 1.8 cubic meters. - two-chamber tank.

Calculation of a septic tank for 4 people

Let us consider in more detail the methodology for calculating the volume of a septic tank, where we will independently estimate the amount of water consumed by one person (Q). As a rule, in the summer, each person takes a shower in the morning, in the evening, for example, takes a bath:

200+(10*7)+100=370 liters per day.

4*370*3/1000=4.44 cubic meters According to the calculations for a private house for 4 people, it will be necessary to install a septic tank with a volume of 4.5 cubic meters - a septic tank - two-chamber or three-chamber.

Calculation of a septic tank for 6 people

According to the above values of the volume of the septic tank by the number of people, it can be assumed that a tank of 3 cubic meters will be enough for 6 people. For an individual calculation of six people, we apply the formula and compare the data with the average values indicated in the table above. Let's say that each person takes a shower for 10 minutes and wash clothes for 2 kg.

200+(10*10)+80=380 liters.

6*380*3/380=6.84 cubic meters

The result obtained is much higher than the average values in the table. In any case, it is necessary to make a calculation in order to avoid incorrect operation of the septic tank. Also, when calculating, it should be taken into account that guests can come to the owners of the house, which will increase the load on the sewer system.

Before starting the construction of sewers, it is necessary to familiarize yourself with the rules and regulations for the construction of autonomous sewers (SNiP 2.04.03-85) "Sewerage". Deviation from the norms and rules, as a rule, leads to equipment failure, which in turn can cause an environmental problem. In this case, the legislation of the Russian Federation provides for the imposition of penalties on the owner of a private house.

To avoid unpleasant consequences as a result of a violation of the installation technology and calculation of the volume of a septic tank, it is necessary to consult with specialists. The company "Moskomplekt" has many years of experience in installing septic tanks for a private house, cottages, etc.

See for yourself, give us a call and we will answer any questions you may have. It is possible to install a sewer system on your own, but in any case, it is better to consult with a specialist before starting work. Call and our experts will answer all your questions.