Calculation of fluid passage through a pipe. Pipeline capacity

The calculator is easy to use – enter the data and get the result. But sometimes this is not enough - accurate calculation of the pipe diameter is only possible with manual calculation using formulas and correctly selected coefficients. How to calculate the diameter of a pipe based on water flow? How to determine the size of a gas line?

When calculating the required pipe diameter, professional engineers most often use special programs that can calculate and produce accurate results based on known parameters. It is much more difficult for an amateur builder to carry out calculations independently to organize water supply, heating, and gasification systems. Therefore, most often when constructing or reconstructing a private house, the recommended pipe sizes are used. But not always standard advice can take into account all the nuances individual construction, therefore, it is necessary to manually perform a hydraulic calculation in order to correctly select the diameter of the pipe for heating and water supply.

Calculation of pipe diameter for water supply and heating

The main criterion for selecting a heating pipe is its diameter. This indicator determines how effective the heating of the house will be and the service life of the system as a whole. With a small diameter, increased pressure may occur in the lines, which will cause leaks, increased load on pipes and metal, which will lead to problems and endless repairs. With a large diameter, the heat transfer of the heating system will tend to zero, and cold water will simply ooze out of the tap.

Pipe capacity

The diameter of the pipe directly affects the throughput of the system, that is, in this case, what matters is the amount of water or coolant passing through the section per unit time. The more cycles (movements) in the system over a certain period of time, the more efficient the heating is. For water supply pipes, the diameter affects the initial water pressure - a suitable size will only maintain the pressure, and an increased one will reduce it.

The diameter of the water supply and heating system, the number of radiators and their sections are selected, and the optimal length of the lines is determined.

Since the throughput of the pipe is a fundamental factor in the choice, you should decide what, in turn, affects the throughput of water in the main.

Table 1. Bandwidth pipes depending on water flow and diameter
Consumption Bandwidth
Du pipe 15 mm 20 mm 25 mm 32 mm 40 mm 50 mm 65 mm 80 mm 100 mm
Pa/m - mbar/m less than 0.15 m/s 0.15 m/s 0.3 m/s
90,0 - 0,900 173 403 745 1627 2488 4716 9612 14940 30240
92,5 - 0,925 176 407 756 1652 2524 4788 9756 15156 30672
95,0 - 0,950 176 414 767 1678 2560 4860 9900 15372 31104
97,5 - 0,975 180 421 778 1699 2596 4932 10044 15552 31500
100,0 - 1,000 184 425 788 1724 2632 5004 10152 15768 31932
120,0 - 1,200 202 472 871 1897 2898 5508 11196 17352 35100
140,0 - 1,400 220 511 943 2059 3143 5976 12132 18792 38160
160,0 - 1,600 234 547 1015 2210 3373 6408 12996 20160 40680
180,0 - 1,800 252 583 1080 2354 3589 6804 13824 21420 43200
200,0 - 2,000 266 619 1151 2486 3780 7200 14580 22644 45720
220,0 - 2,200 281 652 1202 2617 3996 7560 15336 23760 47880
240,0 - 2,400 288 680 1256 2740 4176 7920 16056 24876 50400
260,0 - 2,600 306 713 1310 2855 4356 8244 16740 25920 52200
280,0 - 2,800 317 742 1364 2970 4356 8566 17338 26928 54360
300,0 - 3,000 331 767 1415 3076 4680 8892 18000 27900 56160

Factors influencing the highway's passability:

  1. Water or coolant pressure.
  2. Internal diameter (section) of the pipe.
  3. Total length of the system.
  4. Pipeline material.
  5. Pipe wall thickness.

On the old system, the permeability of the pipe is aggravated by lime and silt deposits, the consequences of corrosion (on metal products). All this together reduces over time the amount of water passing through the section, that is, used lines work worse than new ones.

It is noteworthy that this indicator does not change for polymer pipes - plastic is much less likely than metal to allow slag to accumulate on the walls. Therefore the throughput PVC pipes remains the same as on the day of their installation.


Calculation of pipe diameter based on water flow

Determining the correct water flow

To determine the diameter of the pipe based on the flow rate of the passing liquid, you will need values ​​of true water consumption taking into account all plumbing fixtures: bathtubs, kitchen faucet, washing machine, toilet. Each individual section of the water pipeline is calculated using the formula:

qc = 5× q0 × α, l/s

where qc is the value of water consumed by each device;

q0 is a standardized value, which is determined according to SNiP. We take for a bath - 0.25, for a kitchen faucet 0.12, for a toilet -0.1;

a is a coefficient that takes into account the possibility of simultaneous operation of plumbing fixtures in the room. Depends on the probability value and the number of consumers.

In sections of the main line where water flows for the kitchen and bath, for the toilet and bath, etc. are combined, a probability value is added to the formula. That is, the possibility of simultaneous operation of a kitchen faucet, bathroom faucet, toilet and other appliances.

The probability is determined by the formula:

Р = qhr µ × u/q0 × 3600 × N,

where N is the number of water consumers (appliances);

qhr µ is the maximum hourly water flow that can be accepted according to SNiP. Choose for cold water qhr µ =5.6 l/s, total flow rate 15.6 l/s;

u – number of people using plumbing fixtures.

Example of calculating water consumption:

IN two-story house There is 1 bathroom, 1 kitchen with installed washing machine and dishwasher, shower, 1 toilet. A family of 5 lives in the house. Calculation algorithm:

  1. We calculate the probability P = 5.6 × 5/0.25 × 3600 × 6 = 0.00518.
  2. Then the water consumption for the bathroom will be qc = 5 × 0.25 × 0.00518 = 0.006475 l/s.
  3. For the kitchen qc = 5 × 0.12 × 0.00518 = 0.0031 l/s.
  4. For a toilet, qc = 5 × 0.1 × 0.00518 = 0.00259 l/s.

Calculate the diameter of the pipe

There is a direct relationship between the diameter and the volume of flowing liquid, which is expressed by the formula:

where Q is water flow, m3/s;

d – pipeline diameter, m;

w – flow velocity, m/s.

By transforming the formula, you can select the value of the pipeline diameter, which will correspond to the consumed volume of water:

Yulia Petrichenko, expert

d = √(4Q/πw), m

The water flow rate can be taken from Table 2. There is a more complex method for calculating the flow rate - taking into account losses and the coefficient of hydraulic friction. This is a rather voluminous calculation, but in the end it allows you to get exact value, in contrast to the tabular method.

Table 2. Liquid flow rate in the pipeline depending on its characteristics
Pumped medium Optimal speed in the pipeline, m/s
LIQUIDS Gravity movement:
Viscous liquids 0,1-0,5
Low viscosity liquids 0,5-1
Pumpable:
Suction line 0,8-2
Discharge pipeline 1,5-3
GASES Natural craving 2-4
Low pressure (fans) 4-15
High pressure (compressor) 15-25
COUPLES Overheated 30-50
Saturated vapor at pressure
More than 105 Pa 15-25
(1-0.5)*105 Pa 20-40
(0.5-0.2)*105 Pa 40-60
(0.2-0.05)*105 Pa 60-75

Example: Let's calculate the diameter of the pipe for the bathroom, kitchen and toilet based on the obtained water consumption values. We select from Table 2 the value of the water flow speed in the pressure water supply pipe – 3 m/s.

Calculation of water consumption is carried out before the construction of pipelines and is integral part hydrodynamic calculations. During the construction of highways and industrial pipelines These calculations are made using special programs. When building a domestic pipeline with your own hands, you can carry out the calculation yourself, but it is worth considering that the result obtained will not be as accurate as possible. Read on to learn how to calculate the water consumption parameter.

Factors affecting throughput

The main factor used to calculate the pipeline system is throughput. This indicator is influenced by many various parameters, the most significant of which are:

  1. pressure in the existing pipeline (in the main network, if the pipeline under construction will be connected to an external source). The calculation method taking into account pressure is more complex, but also more accurate, since an indicator such as throughput, that is, the ability to pass a certain amount of water in a certain unit of time, depends on pressure;
  2. total pipeline length. The larger this parameter, the greater the amount of losses that appears during its use and, accordingly, to avoid a pressure drop it is necessary to use pipes of larger diameter. Therefore, this factor is also taken into account by specialists;
  3. the material from which the pipes are made. If for a construction or other highway they are used metal pipes, then the uneven internal surface and the possibility of gradual clogging with sediment contained in the water will lead to a decrease in throughput and, accordingly, a slight increase in diameter. Using plastic pipes(PVC), polypropylene pipes and so the possibility of clogging with deposits is practically excluded. Moreover, the inner surface of plastic pipes is smoother;

  1. pipe section. Based on the internal cross-section of the pipe, you can independently make a preliminary calculation.

There are other factors that are taken into account by experts. But for this article they are not significant.

Method for calculating diameter depending on pipe cross-section

If when calculating a pipeline it is necessary to take into account all of the listed factors, it is recommended to carry out calculations using special programs. If preliminary calculations are sufficient for the construction of the system, then they are carried out in the following sequence:

  • preliminary determination of the amount of water consumption by all family members;
  • count optimal size diameter

How to calculate water consumption in a house

Determine yourself the amount of cold or hot water in the house there are several methods:

  • according to the meter reading. If meters are installed when entering the pipeline into the house, then determining the water consumption per day per person is not a problem. Moreover, with observation over several days, fairly accurate parameters can be obtained;

  • according to the formula.

To determine total consumed water in the room, it is necessary to make a calculation for each plumbing unit (bathtub, shower stall, mixer, etc.) separately. Calculation formula:

Qs = 5 x q0 x P, Where

Qs is an indicator that determines the amount of flow;

q0 — established norm;

P is a coefficient that takes into account the possibility of using several types of plumbing fixtures simultaneously.

The q0 indicator is determined depending on the type of plumbing equipment according to the following table:

Probability P is determined by the following formula:

P = L x N1 / q0 x 3600 x N2, Where

L—peak water flow for 1 hour;

N1 - number of people using plumbing fixtures;

q0 - established standards for a separate plumbing unit;

N2 - number of installed plumbing fixtures.

It is unacceptable to determine water flow without taking into account probability, since the simultaneous use of plumbing fixtures leads to an increase in flow power.

We will calculate the water for specific example. It is necessary to determine water consumption according to the following parameters:

  • 5 people live in the house;
  • 6 units of plumbing equipment are installed: bath, toilet, kitchen sink, washing machine and Dishwasher, installed in the kitchen, shower;
  • peak water flow for 1 hour in accordance with SNiP is set equal to 5.6 l/s.

Determine the probability size:

P = 5.6 x 4 / 0.25 x 3600 x 6 = 0.00415

We determine the water consumption for the bath, kitchen and toilet room:

Qs (baths) = 4 x 0.25 x 0.00518 = 0.00415 (l/s)

Qs (kitchens) = 4 x 0.12 x 0.00518 = 0.002 (l/s)

Qs (toilet) = 4 x 0.4 x 0.00518 = 0.00664 (l/s)

Calculation of the optimal section

To determine the cross section, the following formula is used:

Q = (πd²/4)xW, Where

Q is the calculated amount of water consumed;

d – required diameter;

W is the speed of water movement in the system.

Through the simplest mathematical operations it can be concluded that

d = √(4Q/πW)

The W indicator can be obtained from the table:

The indicators presented in the table are used for approximate calculations. To obtain more accurate parameters, a complex mathematical formula is used.

Let's determine the diameter of the pipes for the bath, kitchen and toilet according to the parameters presented in the example under consideration:

d (for bathroom) = √(4 x 0.00415 / (3.14 x 3)) = 0.042 (m)

d (for kitchen) = √(4 x 0.002 / (3.14 x 3)) = 0.03 (m)

d (for toilet) = √(4 x 0.00664 / (3.14 x 3)) = 0.053 (m)

To determine the cross-section of pipes, the largest calculated indicator. Taking into account the small margin in this example, it is possible to conduct the water supply with pipes with a cross-section of 55 mm.

How to make calculations using a special semi-professional program, watch the video.

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Pipe throughput: simple about complex things

How does the capacity of a pipe change depending on the diameter? What factors other than cross-section influence this parameter? Finally, how to calculate, even approximately, the permeability of a water pipeline with a known diameter? In this article I will try to give the most simple and accessible answers to these questions.

Our task is to learn to count optimal cross section water pipes.

Why is this necessary?

Hydraulic calculation allows you to obtain optimal minimum water pipe diameter value.

On the one hand, there is always a catastrophic shortage of money during construction and repairs, and the price linear meter pipes grows nonlinearly with increasing diameter. On the other hand, an undersized water supply section will lead to an excessive drop in pressure at the end devices due to its hydraulic resistance.

When the flow rate is at the intermediate device, the pressure drop at the end device will lead to the fact that the water temperature with the cold water and hot water taps open will change sharply. As a result, you will either be doused with ice water or scalded with boiling water.

Restrictions

I will deliberately limit the scope of the problems under consideration to the water supply of a small private house. There are two reasons:

  1. Gases and liquids of different viscosities behave completely differently when transported through a pipeline. Consideration of the behavior of natural and liquefied gas, oil and other media would increase the volume of this material several times and would take us far from my specialty - plumbing;
  2. In the case of a large building with numerous plumbing fixtures, for the hydraulic calculation of the water supply it will be necessary to calculate the probability of simultaneous use of several water points. IN small house the calculation is performed for peak consumption by all available devices, which greatly simplifies the task.

Factors

Hydraulic calculation of a water supply system is a search for one of two quantities:

  • Calculation of pipe capacity for a known cross-section;
  • Calculation of the optimal diameter with a known planned flow rate.

In real conditions (when designing a water supply system), it is much more common to perform the second task.

Everyday logic dictates that the maximum water flow through a pipeline is determined by its diameter and inlet pressure. Alas, the reality is much more complicated. The fact is that the pipe has hydraulic resistance: Simply put, the flow is slowed down by friction against the walls. Moreover, the material and condition of the walls predictably influence the degree of braking.

Here full list Factors affecting the performance of a water pipe:

  • Pressure at the beginning of the water supply (read - pressure in the line);
  • Slope pipes (change in its height above the conditional ground level at the beginning and end);

  • Material walls Polypropylene and polyethylene have much less roughness than steel and cast iron;
  • Age pipes. Over time, steel becomes overgrown with rust and lime deposits, which not only increase roughness, but also reduce the internal clearance of the pipeline;

This does not apply to glass, plastic, copper, galvanized and metal-polymer pipes. Even after 50 years of operation they are in new condition. The exception is silting of the water supply when large quantities suspensions and the absence of filters at the inlet.

  • Quantity and angle turns;
  • Diameter changes water supply;
  • Presence or absence welds, solder burrs and connecting fittings;

  • Shut-off valves. Even full bore Ball Valves provide a certain resistance to the flow.

Any calculation of pipeline capacity will be very approximate. Willy-nilly, we will have to use average coefficients typical for conditions close to ours.

Torricelli's Law

Evangelista Torricelli, who lived at the beginning of the 17th century, is known as a student of Galileo Galilei and the author of the very concept of atmospheric pressure. He also owns a formula describing the flow rate of water pouring out of a vessel through a hole of known dimensions.

For the Torricelli formula to work, you must:

  1. So that we know the water pressure (the height of the water column above the hole);

One atmosphere under Earth's gravity is capable of raising a water column by 10 meters. Therefore, pressure in atmospheres is converted into pressure by simply multiplying by 10.

  1. So that there is a hole significantly smaller than the diameter of the vessel, thus eliminating loss of pressure due to friction against the walls.

In practice, Torricelli's formula allows one to calculate the flow of water through a pipe with an internal cross-section of known dimensions at a known instantaneous pressure at the time of flow. Simply put: to use the formula, you need to install a pressure gauge in front of the tap or calculate the pressure drop in the water supply system at a known pressure in the line.

The formula itself looks like this: v^2=2gh. In it:

  • v is the flow velocity at the outlet of the hole in meters per second;
  • g is the acceleration of the fall (for our planet it is equal to 9.78 m/s^2);
  • h is the pressure (the height of the water column above the hole).

How will this help in our task? And the fact that fluid flow through the hole(the same bandwidth) is equal to S*v, where S is the cross-sectional area of ​​the hole and v is the flow velocity from the above formula.

Captain Obviousness suggests: knowing the cross-sectional area, it is not difficult to determine the internal radius of the pipe. As you know, the area of ​​a circle is calculated as π*r^2, where π is taken to be rounded equal to 3.14159265.

In this case, Torricelli’s formula will look like v^2=2*9.78*20=391.2. The square root of 391.2 is rounded to 20. This means that water will pour out of the hole at a speed of 20 m/s.

We calculate the diameter of the hole through which the flow flows. Converting the diameter to SI units (meters), we get 3.14159265*0.01^2=0.0003141593. Now let’s calculate the water consumption: 20*0.0003141593=0.006283186, or 6.2 liters per second.

Back to reality

Dear reader, I would venture to guess that you do not have a pressure gauge installed in front of the mixer. Obviously, for a more accurate hydraulic calculation, some additional data is needed.

Typically, the calculation problem is solved in reverse: given the known water flow through the plumbing fixtures, the length of the water pipe and its material, a diameter is selected that ensures the pressure drop to acceptable values. The limiting factor is the flow rate.

Reference data

The normal flow rate for internal water supply systems is considered to be 0.7 - 1.5 m/s. Exceeding the last value leads to the appearance of hydraulic noise (primarily at bends and fittings).

Water consumption standards for plumbing fixtures are easy to find in regulatory documentation. In particular, they are given in the appendix to SNiP 2.04.01-85. To save the reader from lengthy searches, I will provide this table here.

The table shows data for mixers with aerators. Their absence equalizes the flow through the mixers of the sink, washbasin and shower with the flow through the mixer when setting the bath.

Let me remind you that if you want to calculate the water supply of a private house with your own hands, add up the water consumption for all installed devices. If these instructions are not followed, you will be in for surprises like a sharp drop in the temperature in the shower when you turn on the hot water tap.

If the building has a fire water supply, 2.5 l/s is added to the planned flow rate for each hydrant. For fire water supply, the flow speed is limited to 3 m/s: In the event of a fire, hydraulic noise is the last thing that will irritate residents.

When calculating the pressure, it is usually assumed that at the device farthest from the input it should be at least 5 meters, which corresponds to a pressure of 0.5 kgf/cm2. Some plumbing fixtures (instantaneous water heaters, automatic filler valves) washing machines etc.) simply do not work if the pressure in the water supply is below 0.3 atmospheres. In addition, it is necessary to take into account hydraulic losses on the device itself.

On the picture - instantaneous water heater Atmor Basic. It turns on heating only at a pressure of 0.3 kgf/cm2 and above.

Flow, diameter, speed

Let me remind you that they are linked together by two formulas:

  1. Q = SV. Water consumption in cubic meters per second equal to area sections in square meters, multiplied by the flow speed in meters per second;
  2. S = π r^2. The cross-sectional area is calculated as the product of pi and the square of the radius.

Where to get radius values internal section?

  • For steel pipes, with a minimum error it is equal to half the remote control(conditional bore used to mark rolled pipes);
  • For polymer, metal-polymer, etc. inner diameter is equal to the difference between the outer one, which is used to mark the pipes, and twice the wall thickness (it is also usually present in the marking). The radius, accordingly, is half the internal diameter.

  1. The internal diameter is 50-3*2=44 mm, or 0.044 meters;
  2. The radius will be 0.044/2=0.022 meters;
  3. The internal cross-sectional area will be equal to 3.1415*0.022^2=0.001520486 m2;
  4. At a flow rate of 1.5 meters per second, the flow rate will be 1.5*0.001520486=0.002280729 m3/s, or 2.3 liters per second.

Loss of pressure

How to calculate how much pressure is lost in a water pipeline with known parameters?

The simplest formula for calculating the pressure drop is H = iL(1+K). What do the variables in it mean?

  • H is the desired pressure drop in meters;
  • i — hydraulic slope of a water pipe meter;
  • L is the length of the water pipeline in meters;
  • K— coefficient, which makes it possible to simplify the calculation of pressure drop on shut-off valves and. It is tied to the purpose of the water supply network.

Where can I get the values ​​of these variables? Well, except for the length of the pipe, no one has canceled the tape measure yet.

Coefficient K is taken equal to:

With a hydraulic slope the picture is much more complicated. The resistance offered by a pipe to flow depends on:

  • Internal section;
  • Wall roughness;
  • Flow rates.

A list of values ​​for 1000i (hydraulic slope per 1000 meters of water supply) can be found in Shevelev’s tables, which, in fact, serve for hydraulic calculations. The tables are too large for an article because they provide 1000i values ​​for all possible diameters, flow rates and materials, adjusted for service life.

Here is a small fragment of Shevelev’s table for plastic pipe size 25 mm.

The author of the tables gives pressure drop values ​​not for the internal section, but for standard sizes, which are used to mark pipes, adjusted for wall thickness. However, the tables were published in 1973, when the corresponding market segment had not yet been formed.
When calculating, keep in mind that for metal-plastic it is better to take values ​​corresponding to a pipe that is one step smaller.

Let's use this table to calculate the pressure drop by polypropylene pipe with a diameter of 25 mm and a length of 45 meters. Let's agree that we are designing a water supply system for household purposes.

  1. At a flow speed as close as possible to 1.5 m/s (1.38 m/s), the 1000i value will be equal to 142.8 meters;
  2. The hydraulic slope of one meter of pipe will be equal to 142.8/1000=0.1428 meters;
  3. The correction factor for domestic water supply systems is 0.3;
  4. The formula as a whole will take the form H=0.1428*45(1+0.3)=8.3538 meters. This means that at the end of the water supply system, with a water flow rate of 0.45 l/s (the value from the left column of the table), the pressure will drop by 0.84 kgf/cm2 and at 3 atmospheres at the inlet it will be quite acceptable 2.16 kgf/cm2.

This value can be used to determine consumption according to Torricelli formula. The calculation method with an example is given in the corresponding section of the article.

In addition, to calculate the maximum flow through a water supply with known characteristics, you can select in the “flow” column full table Shevelev is a value at which the pressure at the end of the pipe does not fall below 0.5 atmospheres.

Conclusion

Dear reader, if the given instructions, despite being extremely simplified, still seem tedious to you, just use one of the many online calculators. As always, Additional information can be found in the video in this article. I would appreciate your additions, corrections and comments. Good luck, comrades!

July 31, 2016

If you want to express gratitude, add a clarification or objection, or ask the author something - add a comment or say thank you!

Water consumption parameters:

  1. The diameter of the pipe, which also determines further throughput.
  2. The size of the pipe walls, which will then determine the internal pressure in the system.

The only thing that does not affect consumption is the length of communications.

If the diameter is known, the calculation can be carried out using the following data:

  1. Structural material for pipe construction.
  2. Technology affecting the pipeline assembly process.

The characteristics affect the pressure inside the water supply system and determine the water flow.

If you are looking for an answer to the question of how to determine water consumption, then you must understand two calculation formulas that determine the parameters of use.

  1. The formula for calculating per day is Q=ΣQ×N/100. Where ΣQ is the annual daily water use per inhabitant, and N is the number of residents in the building.
  2. The formula for calculating per hour is q=Q×K/24. Where Q is the daily calculation, and K is the ratio according to SNiP uneven consumption (1.1-1.3).

These simple calculations can help determine the consumption, which will show the needs and requirements of a given home. There are tables that can be used to calculate liquids.

Reference data for water calculations

When using tables, you should calculate all the faucets, bathtubs and water heaters in the house. Table SNiP 2.04.02-84.

Standard consumption rates:

  • 60 liters – 1 person.
  • 160 liters - for 1 person, if the house has better plumbing.
  • 230 liters - for 1 person, in a house with high-quality running water and a bathroom.
  • 350 liters - for 1 person with running water, built-in appliances, bath, toilet.

Why calculate water according to SNiP?

How to determine water consumption for every day is not the most popular information among ordinary residents of the house, but pipeline installation specialists need this information even less. And for the most part, they need to know what the diameter of the connection is and what pressure it maintains in the system.

But to determine these indicators, you need to know how much water is needed in the pipeline.

A formula that helps determine the diameter of the pipe and the speed of fluid flow:

The standard fluid speed in a system without pressure is 0.7 m/s and 1.9 m/s. And the speed from an external source, for example a boiler, is determined by the source’s passport. Knowing the diameter determines the flow rate in communications.

Calculation of water pressure loss

The loss of water flow is calculated taking into account the pressure drop using one formula:

In the formula, L – denotes the length of the connection, and λ – friction loss, ρ – ductility.

The friction indicator varies from the following values:

  • coating roughness level;
  • obstacles in the equipment at locking points;
  • fluid flow speed;
  • pipeline length.

Easy calculation

Knowing pressure loss, fluid velocity in pipes and volume required water, how to determine water flow and pipeline sizes becomes much clearer. But in order to get rid of long calculations, you can use a special table.

Where D is the pipe diameter, q is the consumer water flow, and V is the water speed, i is the course. To determine the values, they must be found in the table and connected in a straight line. The flow rate and diameter are also determined, taking into account the slope and speed. Therefore, the most in a simple way calculation is the use of tables and graphs.

Why are such calculations needed?

When drawing up a plan for the construction of a large cottage with several bathrooms, a private hotel, an organization fire system, it is very important to have more or less accurate information about the transporting capabilities of the existing pipe, taking into account its diameter and pressure in the system. It's all about pressure fluctuations during peak water consumption: such phenomena quite seriously affect the quality of the services provided.

In addition, if the water supply is not equipped with water meters, then when paying for utility services, the so-called. "pipe patency". In this case, the question of the tariffs applied in this case arises quite logically.

It is important to understand that the second option does not apply to private premises (apartments and cottages), where, in the absence of meters, sanitary standards are taken into account when calculating payment: usually this is up to 360 l/day per person.

What determines the permeability of a pipe?

What determines the flow of water in a pipe? round section? It seems that finding the answer should not be difficult: the larger the cross-section of the pipe, the greater the volume of water it can pass in a certain time. At the same time, pressure is also remembered, because the higher the water column, the faster the water will be forced inside the communication. However, practice shows that these are not all the factors influencing water consumption.

In addition to these, the following points must also be taken into account:

  1. Pipe length. As its length increases, the water rubs against its walls more strongly, which leads to a slowdown in flow. Indeed, at the very beginning of the system, water is affected solely by pressure, but it is also important how quickly the next portions have the opportunity to enter the communication. The braking inside the pipe often reaches large values.
  2. Water consumption depends on diameter to a much more complex extent than it seems at first glance. When the pipe diameter is small, the walls resist water flow an order of magnitude more than in thicker systems. As a result, as the pipe diameter decreases, its benefit in terms of the ratio of water flow velocity to internal area over a section of a fixed length decreases. To put it simply, a thick pipeline transports water much faster than a thin one.
  3. Material of manufacture. Another important point, which directly affects the speed of water movement through the pipe. For example, smooth propylene promotes the sliding of water to a much greater extent than rough steel walls.
  4. Duration of service. Over time, steel water pipes develop rust. In addition, it is typical for steel, like cast iron, to gradually accumulate lime deposits. The resistance to water flow of pipes with deposits is much higher than that of new steel products: this difference sometimes reaches up to 200 times. In addition, the overgrowing of the pipe leads to a decrease in its diameter: even if we do not take into account the increased friction, its permeability clearly decreases. It is also important to note that products made of plastic and metal-plastic do not have such problems: even after decades of intensive use, their level of resistance to water flows remains at the original level.
  5. Availability of turns, fittings, adapters, valves contributes to additional inhibition of water flows.

All of the above factors must be taken into account, because we are not talking about some small errors, but about a serious difference of several times. As a conclusion, we can say that a simple determination of the pipe diameter based on water flow is hardly possible.

New ability to calculate water consumption

If the water is used through a tap, this greatly simplifies the task. The main thing in this case is that the size of the water outflow hole is much smaller than the diameter of the water pipe. In this case, the formula for calculating water over the cross section of a Torricelli pipe is applicable: v^2=2gh, where v is the speed of flow through a small hole, g is the acceleration free fall, and h is the height of the water column above the tap (a hole with a cross-section s passes a water volume s*v per unit time). It is important to remember that the term “section” is used not to denote the diameter, but its area. To calculate it, use the formula pi*r^2.

If the water column has a height of 10 meters and the hole has a diameter of 0.01 m, the water flow through the pipe at a pressure of one atmosphere is calculated as follows: v^2=2*9.78*10=195.6. After taking the square root, we get v=13.98570698963767. After rounding to get a simpler speed figure, the result is 14m/s. The cross-section of a hole having a diameter of 0.01 m is calculated as follows: 3.14159265*0.01^2=0.000314159265 m2. As a result, it turns out that the maximum water flow through the pipe corresponds to 0.000314159265*14 = 0.00439822971 m3/s (slightly less than 4.5 liters of water/second). As you can see, in this case, calculating water across the cross-section of a pipe is quite simple. There are also freely available special tables indicating water consumption for the most popular plumbing products, with minimum value diameter of the water pipe.

As you can already understand, there is no universal, simple way to calculate the diameter of a pipeline depending on water flow. However, you can still derive certain indicators for yourself. This is especially true if the system is made of plastic or metal-plastic pipes, and water consumption is carried out by taps with a small outlet cross-section. In some cases, this calculation method is applicable to steel systems, but we are talking primarily about new water pipelines that have not yet become covered with internal deposits on the walls.

Water consumption by pipe diameter: determination of pipeline diameter depending on flow rate, calculation by cross-section, formula for maximum flow rate at pressure in a round pipe


Water consumption by pipe diameter: determination of pipeline diameter depending on flow rate, calculation by cross-section, formula for maximum flow rate at pressure in a round pipe

Water flow through a pipe: is a simple calculation possible?

Is it possible to make any simple calculation of water flow based on the diameter of the pipe? Or the only way is to contact specialists, having previously depicted detailed map all the water pipes in the area?

After all, hydrodynamic calculations are extremely complex...

Our task is to find out how much water this pipe can pass

What is it for?

  1. When independently calculating water supply systems.

If you plan to build big house with several guest baths, a mini-hotel, think over a fire extinguishing system - it is advisable to know how much water a pipe of a given diameter can supply at a certain pressure.

After all, a significant drop in pressure during peak water consumption is unlikely to please residents. And a weak stream of water from a fire hose will most likely be useless.

  1. In the absence of water meters, utilities usually bill organizations "by pipe flow."

Please note: the second scenario does not affect apartments and private houses. If there are no water meters, utilities charge for water according to sanitary standards. For modern well-maintained houses this is no more than 360 liters per person per day.

We must admit: a water meter greatly simplifies relations with utility services

Factors affecting pipe patency

What affects the maximum water flow in a round pipe?

The obvious answer

Common sense dictates that the answer should be very simple. There is a pipe for water supply. There is a hole in it. The larger it is, the more water will pass through it per unit of time. Oh, sorry, still pressure.

Obviously, a column of water 10 centimeters will be forced through a centimeter hole less water than a water column the height of a ten-story building.

So, it depends on the internal cross-section of the pipe and on the pressure in the water supply system, right?

Is anything else really needed?

Correct answer

No. These factors affect consumption, but they are only the beginning of a long list. Calculating water flow based on the diameter of the pipe and the pressure in it is the same as calculating the trajectory of a rocket flying to the Moon based on the apparent position of our satellite.

If you do not take into account the rotation of the Earth, the movement of the Moon in its own orbit, atmospheric resistance and gravity celestial bodies- hardly ours spaceship will hit at least approximately the desired point in space.

How much water will flow out of a pipe with diameter x at line pressure y is influenced not only by these two factors, but also by:

  • Pipe length. The longer it is, the more the friction of water against the walls slows down the flow of water in it. Yes, the water at the very end of the pipe is affected only by the pressure in it, but the following volumes of water must take its place. And the water pipe slows them down, and how.

It is precisely because of the loss of pressure in a long pipe that pumping stations are located on oil pipelines

  • The diameter of the pipe affects water consumption in a much more complex way than “common sense” suggests.. For small-diameter pipes, the wall resistance to flow movement is much greater than for thick pipes.

The reason is that the smaller the pipe, the less favorable in terms of water flow rate the ratio of internal volume and surface area at a fixed length.

Simply put, it is easier for water to move through a thick pipe than through a thin one.

  • Wall material is another most important factor, on which the speed of water movement depends. If water slides on smooth polypropylene, like the loin of a clumsy lady on a sidewalk in icy conditions, then rough steel creates much greater resistance to flow.
  • The age of the pipe also greatly affects the permeability of the pipe.. Steel water pipes They rust; in addition, steel and cast iron become overgrown with lime deposits over years of use.

An overgrown pipe has much greater resistance to flow (resistance to a polished new steel pipe and rusty differ 200 times!). Moreover, areas inside the pipe due to overgrowth reduce their clearance; even in ideal conditions Much less water will pass through an overgrown pipe.

Do you think it makes sense to calculate the permeability by the diameter of the pipe at the flange?

Please note: the surface condition of plastic and metal-polymer pipes does not deteriorate over time. After 20 years, the pipe will offer the same resistance to water flow as at the time of installation.

  • Finally, any turn, diameter transition, various shut-off valves and fittings - all this also slows down the flow of water.

Ah, if only the above factors could be neglected! However, we are not talking about deviations within the error limits, but about a difference by several times.

All this leads us to a sad conclusion: a simple calculation of water flow through a pipe is impossible.

A ray of light in a dark kingdom

In the case of water flow through a tap, however, the task can be dramatically simplified. The main condition for a simple calculation: the hole through which water is poured must be negligibly small compared to the diameter of the water supply pipe.

Then Torricelli's law applies: v^2=2gh, where v is the flow rate from a small hole, g is the acceleration of free fall, and h is the height of the water column that stands above the hole. In this case, a volume of liquid s*v will pass through a hole with a cross-section s per unit time.

The master left you a gift

Don't forget: the cross-section of a hole is not a diameter, it is an area equal to pi*r^2.

For a water column of 10 meters (which corresponds to an excess pressure of one atmosphere) and a hole with a diameter of 0.01 meters, the calculation will be as follows:

We extract Square root and we get v=13.98570698963767. For simplicity of calculations, we round the value of the flow speed to 14 m/s.

The cross-section of a hole with a diameter of 0.01 m is equal to 3.14159265*0.01^2=0.000314159265 m2.

Thus, the water flow through our hole will be equal to 0.000314159265*14=0.00439822971 m3/s, or slightly less than four and a half liters per second.

As you can see, in this version the calculation is not very complicated.

In addition, in the appendix to the article you will find a table of water consumption for the most common plumbing fixtures, indicating the minimum diameter of the connection.

Conclusion

That's all in a nutshell. As you can see, universal simple solution We have not found; however, we hope you find the article useful. Good luck!

How to calculate pipe capacity

Calculating throughput is one of the most complex tasks when laying a pipeline. In this article we will try to figure out exactly how this is done for different types pipelines and pipe materials.

High flow pipes

Capacity is an important parameter for any pipes, canals and other heirs of the Roman aqueduct. However, the throughput capacity is not always indicated on the pipe packaging (or on the product itself). In addition, the layout of the pipeline also determines how much liquid the pipe passes through the cross-section. How to correctly calculate the throughput of pipelines?

Methods for calculating pipeline capacity

There are several methods for calculating this parameter, each of which is suitable for a particular case. Some symbols important when determining pipe capacity:

Outer diameter is the physical size of the pipe cross-section from one edge of the outer wall to the other. In calculations it is designated as Dn or Dn. This parameter is indicated in the labeling.

Nominal diameter is the approximate value of the diameter of the internal section of the pipe, rounded to the nearest whole number. In calculations it is designated as Du or Du.

Physical methods for calculating pipe capacity

Pipe throughput values ​​are determined using special formulas. For each type of product - for gas, water supply, sewerage - there are different calculation methods.

Tabular calculation methods

There is a table of approximate values ​​created to make it easier to determine the capacity of pipes in apartment wiring. In most cases, high precision is not required, so the values ​​can be applied without complex calculations. But this table does not take into account the decrease in throughput due to the appearance of sedimentary growths inside the pipe, which is typical for old highways.

There is an exact table for calculating capacity, called the Shevelev table, which takes into account the pipe material and many other factors. These tables are rarely used when laying water pipes in an apartment, but in a private house with several non-standard risers they can be useful.

Calculation using programs

Modern plumbing companies have special computer programs to calculate pipe capacity, as well as many other similar parameters. In addition, online calculators have been developed, which, although less accurate, are free and do not require installation on a PC. One of the stationary programs “TAScope” is a creation of Western engineers, which is shareware. Large companies use "Hydrosystem" - this is a domestic program that calculates pipes according to criteria that affect their operation in the regions of the Russian Federation. In addition to hydraulic calculations, it allows you to calculate other pipeline parameters. The average price is 150,000 rubles.

How to calculate the capacity of a gas pipe

Gas is one of the most difficult materials to transport, in particular because it tends to be compressed and therefore is able to leak through the smallest gaps in pipes. To calculate the capacity of gas pipes (as well as to design gas system in general) have special requirements.

Formula for calculating the capacity of a gas pipe

The maximum throughput of gas pipelines is determined by the formula:

Qmax = 0.67 DN2 * p

where p is equal to the operating pressure in the gas pipeline system + 0.10 MPa or absolute gas pressure;

Du – conditional diameter of the pipe.

There is a complex formula for calculating the capacity of a gas pipe. It is usually not used when carrying out preliminary calculations, as well as when calculating a household gas pipeline.

Qmax = 196.386 DN2 * p/z*T

where z is the compressibility coefficient;

T is the temperature of the transported gas, K;

According to this formula, the direct dependence of the temperature of the moving medium on pressure is determined. The higher the T value, the more the gas expands and presses on the walls. Therefore, when calculating large highways, engineers take into account possible weather conditions in the area where the pipeline runs. If the nominal value of the pipe DN is less than the gas pressure generated by high temperatures in summer (for example, at +38...+45 degrees Celsius), then damage to the main line is likely. This entails the leakage of valuable raw materials and creates the possibility of an explosion in a section of the pipe.

Table of gas pipe capacities depending on pressure

There is a table for calculating gas pipeline throughputs for commonly used pipe diameters and nominal operating pressures. To determine the characteristics of the gas main non-standard sizes and pressure will require engineering calculations. The pressure, speed and volume of gas are also affected by the outside air temperature.

The maximum speed (W) of the gas in the table is 25 m/s, and z (compressibility coefficient) is 1. The temperature (T) is 20 degrees Celsius or 293 Kelvin.

Sewer pipe capacity

The throughput of a sewer pipe is an important parameter that depends on the type of pipeline (pressure or free-flow). The calculation formula is based on the laws of hydraulics. In addition to labor-intensive calculations, tables are used to determine sewer capacity.

Hydraulic calculation formula

For hydraulic calculation of sewerage, it is necessary to determine the unknowns:

  1. pipeline diameter Du;
  2. average flow velocity v;
  3. hydraulic slope l;
  4. degree of filling h/Dn (calculations are based on the hydraulic radius, which is associated with this value).

In practice, they are limited to calculating the value of l or h/d, since the remaining parameters are easy to calculate. In preliminary calculations, the hydraulic slope is considered to be equal to the slope of the earth’s surface, at which the movement Wastewater will not be lower than the self-cleaning speed. Speed ​​values, as well as maximum h/DN values ​​for household networks can be found in Table 3.

In addition, there is a normalized value minimum slope for pipes with small diameter: 150 mm

(i=0.008) and 200 (i=0.007) mm.

The formula for volumetric fluid flow looks like this:

where a is the open cross-sectional area of ​​the flow,

v – flow velocity, m/s.

Speed ​​is calculated using the formula:

where R is the hydraulic radius;

C – wetting coefficient;

From this we can derive the formula for hydraulic slope:

This parameter is used to determine this parameter if calculation is necessary.

where n is the roughness coefficient, having values ​​from 0.012 to 0.015 depending on the pipe material.

The hydraulic radius is considered equal to the normal radius, but only when the pipe is completely filled. In other cases, use the formula:

where A is the area of ​​the transverse fluid flow,

P is the wetted perimeter, or the transverse length of the inner surface of the pipe that touches the liquid.

Capacity tables for free-flow sewer pipes

The table takes into account all the parameters used to perform the hydraulic calculation. The data is selected according to the pipe diameter and substituted into the formula. Here the volumetric flow rate of liquid q passing through the cross-section of the pipe has already been calculated, which can be taken as the throughput of the line.

In addition, there are more detailed Lukin tables containing ready-made throughput values ​​for pipes of different diameters from 50 to 2000 mm.

Capacity tables for pressure sewer systems

In the capacity tables for sewerage pressure pipes, the values ​​depend on the maximum degree of filling and the design average speed waste water.

Water pipe capacity

Water pipes are the most commonly used pipes in a home. And since there is a large load on them, the calculation of the throughput of the water main becomes an important condition reliable operation.

Pipe patency depending on diameter

Diameter is not the most important parameter when calculating the patency of a pipe, but it also affects its value. The larger the internal diameter of the pipe, the higher the permeability, and also the lower the chance of blockages and plugs. However, in addition to the diameter, it is necessary to take into account the coefficient of friction of water against the pipe walls ( table value for each material), the length of the line and the difference in fluid pressure at the inlet and outlet. In addition, the number of elbows and fittings in the pipeline will greatly influence the flow rate.

Table of pipe capacity by coolant temperature

The higher the temperature in the pipe, the lower its throughput, since the water expands and thereby creates additional friction. For plumbing this is not important, but in heating systems is a key parameter.

There is a table for calculations of heat and coolant.

Table of pipe capacity depending on coolant pressure

There is a table describing the capacity of pipes depending on pressure.

Table of pipe capacity depending on diameter (according to Shevelev)

The tables of F.A. and A.F. Shevelev are one of the most accurate tabular methods calculation of water supply capacity. In addition, they contain all the necessary calculation formulas for each specific material. This is a lengthy piece of information that is most often used by hydraulic engineers.

The tables take into account:

  1. pipe diameters – internal and external;
  2. wall thickness;
  3. service life of the water supply system;
  4. line length;
  5. purpose of pipes.

Pipe throughput depending on diameter, pressure: tables, calculation formulas, online calculator


Calculating capacity is one of the most difficult tasks when laying a pipeline. In this article we will try to figure out exactly how this is done for different types of pipelines and pipe materials.