When laying water networks in a country house or a mini-hotel, pipe patency must be taken into account. It shows the maximum amount of fluid passing through the trunk network for a specific time interval. This allows you to find out how much moisture will leak out with open taps, and compare the obtained value with the estimated water consumption by the residents of the house. The easiest way to calculate the flow rate of water according to the diameter of the pipe and pressure, since these indicators are easy to find.
The need to calculate water flow by pipe diameter and pressure
When designing a large country house or guesthouse, it is necessary to determine how much water will be needed for its residents or guests, and whether the water supply capacity will correspond to these costs. If the pressure decreases with a significant expenditure, this will lead to the inability to use sanitary equipment. When creating a fire hazard situation, small ignition will be difficult to extinguish. Therefore, the calculation of water consumption and pipeline permeability in a private house is carried out before the start of the construction of the building.
Estimated indicators will help you choose the pipe of the desired cross section with a suitable wall thickness and determine the material of their manufacture. Also, in accordance with these values, the technology for installing the trunk is selected.
The easiest way to calculate how much water is consumed per hour, day or month, if a meter is installed. If there is no metering device, according to the standards, one person is able to spend the following volume of cold water daily:
- cooking - 3 l;
- the use of a washing machine - about 4 l;
- toilet procedures - 15 l;
- morning or evening shower - 30 l;
- bath intake - 200 l.
In a private house with an autonomous water supply, hot water is created by heating cold using boilers or gas stoves, so the consumption of the latter increases. A day here for the needs of one person can go 330 liters of water. Per month, this number will be approximately 10,230 liters, per hour - 13.75 liters.
Similar regulations are approximate. They do not take into account factors such as pet care, replacing water in aquariums and a pool, washing a car and watering plantings. You also need to consider the work schedule of residents and seasonality. But average indicators are needed so that there is something to start from in the calculations.
Owners of private enterprises also need to know the estimated maximum flow rates. In the absence of water meters, public utilities calculate the volume of water consumption depending on the capacity of the pipes. If the owner of the premises knows these indicators, he will be able to control the calculations and will not pay too much.
Factors Affecting Calculations
The determination of pipe cross-flow and, accordingly, the maximum water consumption, depends on many factors:
- The length of the water main. The longer the length, the lower the speed capabilities of the water flow due to the action of friction.
- Tube section. The walls of narrow pipelines give increased resistance. The smaller the inner diameter, the lower the ratio of the speed value of the water flow to the surface area in a certain area, which means that the traffic will be worse. In large cross-sections, fluid flows faster.
- The presence of turning sections. The complex configuration of the pipeline slows down the speed of the water flow in it. The same goes for fittings. Any taps, adapters and couplings inhibit the movement of fluid.
It is also important to consider the material of the pipe segments.This affects both the network throughput and the duration of the service. Metal water pipes tend to deform over time under the influence of rust, accumulate corrosion and lime deposits from the inside, which greatly reduces throughput. The latter is characteristic not only for steel pipes, but also for cast-iron pipes, although they are less susceptible to corrosion.
Resistance to water flow in a clogged line is much higher than that of a new pipeline: indicators can vary 200 times. The DHW pipes become especially clogged.
Polymer highways maintain almost the same throughput throughout the entire life cycle. Plastic is not subject to corrosion, it is not afraid of accumulations of mold and fungus, due to this, blockages in the pipeline are extremely rare.
Settlement Methods
To determine the water consumption of the highway, three calculation methods are used:
- Physical method. To determine the required value, formulas are applied. They use parameters such as pipe diameter, water pressure and the speed of movement of the contents of the pipes in the system.
- Application tables. A fairly easy method, involving the selection of the necessary indicators in the table and clarification on their basis of the necessary data.
- Use of computer programs. There are quite a few such options on the World Wide Web. You can find out the throughput and water flow for pipelines made of various materials, simply by entering the required known data.
To calculate the expense indicators before building a country house, the easiest way to use online calculators. By entering the pressure and diameter of the pipes, you will get a figure of the probable flow rate. It will not be perfectly accurate, but such a method will not require any calculations. To refine the data, check the software calculation with the table values.
Application Tables
Excluding calculating, this method is the easiest. Several tables have been developed: you can choose the one that is suitable depending on the known data. In SNiP 2.04.01-85, it is proposed to calculate the water flow rate for the outer section of the pipe. To do this, use the table of the maximum flow rate of water passing through the pipe of a certain external diameter:
| Pipe girth (mm) | Water consumption | |
| In l / min | Per cube / hour | |
| 20 | 15 | 0,9 |
| 25 | 30 | 1,8 |
| 32 | 50 | 3 |
| 40 | 80 | 4,8 |
| 50 | 120 | 7,2 |
| 63 | 190 | 11,4 |
This is the simplest calculation table, in it you need to know only the coverage of the pipe. To clarify the data, you can enter additional indicators - wall thickness and internal diameter. Such tables are easy to find on the Internet for pipelines of various materials.
When calculating the discharge maximums in the water main, not only the diametric indicator, but also the flow pressure are taken into account.
Another table allows you to identify the maximum flow rate, based on the above values:
| Consumption | Throughput | |||||||||
| Pipe section (mm) | 15 | 20 | 25 | 32 | 40 | 50 | 65 | 80 | 100 | |
| Pa / m | Mbar / m | Less than 0.15 m / s | 0.15 m / s | 0.3 m / s | ||||||
| 90 | 0,9 | 173 | 403 | 745 | 1627 | 2488 | 4716 | 9612 | 14940 | 30240 |
| 92,5 | 0,925 | 176 | 407 | 756 | 1652 | 2524 | 4788 | 9756 | 15156 | 30672 |
| 95 | 0,95 | 176 | 414 | 767 | 1678 | 2560 | 4860 | 9900 | 15372 | 31104 |
| 97,5 | 0,975 | 180 | 421 | 778 | 1699 | 2596 | 4932 | 10044 | 15552 | 31500 |
| 100 | 1000 | 184 | 425 | 788 | 1724 | 2632 | 5004 | 10152 | 15768 | 31932 |
| 120 | 1200 | 202 | 472 | 871 | 1897 | 2898 | 5508 | 11196 | 17352 | 35100 |
| 140 | 1400 | 220 | 511 | 943 | 2059 | 3143 | 5976 | 12132 | 18792 | 38160 |
| 160 | 1600 | 234 | 547 | 1015 | 2210 | 3373 | 6408 | 12996 | 20160 | 40680 |
| 180 | 1800 | 252 | 583 | 1080 | 2354 | 3589 | 6804 | 13824 | 21420 | 43200 |
| 200 | 2000 | 266 | 619 | 1151 | 2488 | 3780 | 7200 | 14580 | 22644 | 45720 |
| 220 | 2200 | 281 | 652 | 1202 | 2617 | 3996 | 7560 | 15336 | 23760 | 47880 |
| 240 | 2400 | 288 | 680 | 1256 | 2740 | 4176 | 7920 | 16056 | 24876 | 50400 |
| 260 | 2600 | 306 | 713 | 1310 | 2855 | 4356 | 8244 | 16740 | 25920 | 52200 |
| 280 | 2800 | 317 | 742 | 1364 | 2970 | 4356 | 8568 | 17338 | 26928 | 54360 |
| 300 | 3000 | 331 | 767 | 1415 | 3078 | 4680 | 8892 | 18000 | 27900 | 56160 |
The average pressure value varies from 1.5 to 4 bar. The use of additional pressure devices will affect the flow rate. When calculating the maximum flow rate when the fluid flows through the pipe, not only the number of taps, but also the number of other consumers is taken into account.
Using formulas
To calculate the water flow based on the cross section of the pipes and the pressure in their walls, several equations are used. The simplest formula is q = π × d² / 4 × V.
- q - flow rate of fluid in liters;
- d is the pipe diameter in centimeters;
- V is the speed of the water stream.
In home highways, powered from a water tower without connecting pumping devices, its value will be 0.7 - 1.9 m / s. If any pressure equipment is connected, then in the technical documentation there is data on the coefficient of the created pressure and the speed indicator of the transported liquid
When calculating the possible flow rate of the liquid, it is necessary to take into account the possible pressure drop.To calculate this indicator, the standard equation Δp = (λL / d) ρw² / 2 is taken as the basis.
- L is the length of the pipe;
- d is its diameter;
- ρ is the density of water;
- w is the speed of the water flow;
- λ is the coefficient of friction.
The latter is detected depending on the speed and cross section of the highway according to the tables.
Further, knowing the indicators of potential flow rate and pressure loss, you can use tables and graphs to identify the exact value of the flow rate of the fluid in specific pipes, or use calculators to calculate, which is easier. If desired, you can even calculate the water consumption in liters for one specific procedure in a particular house.
Knowing the indicators of the maximum water flow in a particular pipeline, you can draw up the correct draft of the position of the main network, taking into account all connected water heaters. Also, an understanding of specific numbers will save water and electricity when connecting pressure devices. With the right choice of values there will be no reason for concern due to the fact that when you open the tap in the kitchen, the water in the shower will turn into a thin stream due to a decrease in pressure.
