How to calculate the pressure in the pipe

In every modern house one of the main conditions of comfort is running water. And with the advent of new technology that requires connecting to the water supply, his role in the house has become very important. Many people have no idea how to do without a washing machine, boiler, dishwasher, etc. But each of these devices for proper operation requires a certain pressure of water coming from the water supply system. And now, a person who has decided to install a new water supply system in his house, is thinking about how to calculate the pressure in the pipe so that all sanitary appliances work well.

Requirements of modern plumbing

Modern plumbing must meet all the requirements and specifications. At the exit of the tap water should flow smoothly, without jerks. Consequently, there should be no pressure drops in the system when parsing water. Piping water should not create noise, have impurities of air and other extraneous accumulations that adversely affect ceramic faucets and other plumbing. To avoid these unpleasant incidents, the water pressure in the pipe should not fall below its minimum when parsing water.

Tip! The minimum water pressure should be 1.5 atmospheres. This pressure is enough for the dishwasher and washing machine.

It is necessary to take into account one more important characteristic of the water supply, related to the flow of water. In any dwelling there is not one point of analysis of water. Therefore, the calculation of the plumbing should fully meet the water demand of all plumbing devices with simultaneous inclusion. This parameter is achieved not only by pressure, but also by the volume of incoming water that a pipe of a certain cross section can miss. In simple terms, before installation, you need to perform some kind of hydraulic calculation of the water supply system, taking into account water flow and pressure.

Before calculating, let's take a closer look at two concepts such as pressure and flow to understand their essence.

Pressure

As you know, the central water supply in the past was connected to a water tower. It is this tower that creates pressure in the water supply network. The unit of pressure is the atmosphere. Moreover, the pressure does not depend on the size of the tank located at the top of the tower, but only on the height.

Tip! If you pour water into a pipe of ten meters height, then it will create pressure at the lowest point - 1 atmosphere.

Pressure equals meters. One atmosphere equals 10 m of water column. Consider the example of a five-story house. The height of the house is 15 m. Therefore, the height of one floor is 3 meters. The fifteen meter tower will create pressure on the first floor of the 1.5 atmosphere. We calculate the pressure on the second floor: 15-3 = 12 meters of water or 1.2 atmospheres. Having done the further calculation, we will see that there will be no water pressure on the 5th floor. So, in order to provide the fifth floor with water, it is necessary to build a tower of more than 15 meters. And if this, for example - a 25-storey house? No one will build such towers. In modern plumbing using pumps.

Let's calculate the pressure at the outlet of the submersible pump. There is a submersible pump that raises the water to 30 meters of water. So, it creates pressure - 3 atmospheres at its outlet. After the pump is immersed in the well for 10 meters, it will create pressure at ground level - 2 atmospheres, or 20 meters of water.

Consumption

Consider the following factor - water consumption. It directly depends on pressure, and the more it is, the faster the water will move through the pipes. That is, there will be a greater expense. But the thing is that the velocity of water is influenced by the cross section of the pipe along which it moves. And if you reduce the cross section of the pipe, it will increase the resistance of water. Consequently, its amount will be reduced at the exit from the pipe during the same period of time.

At production, during the construction of water pipelines, projects are drawn up in which the hydraulic calculation of the water pipe is calculated using the Bernoulli equation:

Where h_1-2 - shows the loss of pressure at the outlet, after overcoming resistance on the entire section of the water supply system.

Calculate home plumbing

But this, as they say, complex calculations. For home plumbing we use simpler calculations.

Based on the passport data of the machines consumed water in the house, we summarize the total consumption. We add to this figure the consumption of all water faucets in the house. One water tap transmits about 5–6 liters of water per minute through itself. We summarize all the numbers and get the total water consumption in the house. Now, guided by the total flow, we buy a pipe with such a cross section, which will provide all the simultaneously working water fitting devices with the right amount and pressure of water.

When home plumbing will connect to the city network, you will use what they give. Well, if you have a well in your home, buy a pump that will fully provide your network with the right pressure and cost. When buying, follow the pump's passport information.

To select the pipe section, we follow these tables:

In these tables, more demanded pipe parameters are provided. For full familiarization on the Internet you can find more complete tables with calculations of pipes of different diameters.

Here, on the basis of these calculations, and with proper installation, you will provide your plumbing with all the required parameters. If something is not clear, it is better to contact the experts.