How to choose a pump for a water supply system

Recommendation points

• Self-priming pumps
• Pumping stations
• Borehole and well pumps
• Submersible drainage pumps

The country life of a modern person cannot be imagined without the use of pumps. Circulating ones force the coolant to move through the heating system, and pumps for water supply provide drinking water or water for domestic needs.

In this publication, we will talk about those of them that will provide water supply to the house, help to water the site, fill a pool or pond and pump water out of the basement, i.e. about intended for water supply and drainage.

What kind of pumps are there and how not to be mistaken in their choice? The most important factor when choosing a pump for water supply is the depth from which it has to raise water. If the distance to the water mirror is small (up to 8 meters), then the simplest and most convenient way to lift it is to use a self-priming pump.

Self-priming pumps

Self-priming pumps are of several types. Some have a built-in ejector and, due to the vacuum in it, they provide the rise (suction) of water. Ejector pumps make a noticeable noise and, therefore, when used to supply water to a house, they are usually installed outside a residential building, in a technical room. These pumps are also very handy for watering your garden and vegetable garden or filling your pond and pool. In another type of self-priming pump, there is no ejector, and water is sucked in due to a special multi-stage design of the hydraulic part. These pumps run almost silently.

When supplying water to a building, there are two main ways of using a self-priming pump. Firstly, when there is already a storage tank in the house and you just need to fill it with water to use a shower or wash dishes. It is important not to forget to install a sensor in the tank that monitors the water level and turns off the pump before the tank overflows. The same sensor should give the pump a turn-on signal when the liquid level in the tank drops. This system has several disadvantages:

• water from the tank to the consumer flows by gravity, and, accordingly, the water pressure is low;
• you need a special place for a tank in the attic and additional piping to and from the tank to all water heating and plumbing fixtures;
• it is necessary to carefully monitor the automation responsible for turning off the pump when the tank is overfilled. If this system fails, you risk ending up in a house flooded with water. Usually, to prevent flooding at home, the tank is equipped with an overflow pipe that drains the emergency excess water from the house..

There is a second, more preferable option for using a self-priming pump, free from all of the above disadvantages. This is the use of a pump in conjunction with a diaphragm pressure tank.

Pumping stations

A self-priming pump mounted on a diaphragm tank and equipped with a pressure switch is commonly called a pumping station. The membrane tank is a sealed metal vessel, divided into two parts by a membrane. One part of the tank is filled with air under pressure, and in the second the pump pumps water. The relay sets the upper pressure limit to which the air in the membrane tank and, accordingly, the water in the water supply system is compressed. As soon as the set pressure is reached, the pump is switched off. Now you can use the water stored in the membrane tank. If the water consumption is small, then the pump will not turn on every time, and the water will simply come from the tank. And only when the pressure drops to the lower limit set on the relay, the pump will turn on again. Thus, using a self-priming pump in conjunction with a diaphragm tank has the following advantages:

• pressure is created in the water supply system, which is necessary for the operation of many water heating devices;
• the number of pump start-ups and shutdowns is reduced, thereby extending its service life;
• the membrane tank creates a reserve of several tens of liters of water, and in the event of a power outage, you can use this water freely;
• no need to install a storage tank in the attic of the building.

It is also important that the pumping stations are compact enough, lightweight and mobile. The mass of most pumping stations fluctuates around 30 kg, i.e. it can be easily carried by one person.

When installing a pumping station, one must not forget that a check valve must be installed on the hose lowered into the well to prevent water from leaving the system back into the well when the pump is turned off.

The most important parameter characterizing a pumping station is its nominal flow, measured in m ^ 3 / h. This figure tells you how much water you can get in a certain period of time using such a station. Most of the models on the market have a maximum flow in the range of 3-8 m ^ 3 / h and a maximum head that allows you to raise water to a height of 40 to 55 m.

As mentioned above, pumping stations can be located both inside and outside the house. If you are going to use the pump only in the warm season, then there should be no problems with the installation. It is enough to connect the pump to the electrical network, lower the hose into the well and connect the discharge pipe to the water supply network. After performing these simple operations, you can move water from the well inside the house without headaches.

In the case when the pumping station has to work all year round, serious preparatory work will be required. The station will need to be installed in a warm room, and the pipe from the well to the house must be insulated or laid in the ground below the freezing level. To avoid freezing of water in the hose, the well will also have to be insulated.

If in the area of ​​your country house the water level is below 8 meters or the water quality at this level does not suit you, then in any case, ordinary pumping stations will not be able to help you and you will need to consider other options.

In this situation, you can use a submersible borehole or well pump..

Borehole and well pumps

Compared to pumping stations, the choice, installation and connection of a borehole pump is a much more complicated and serious matter. And the prices for high-quality Western European borehole pumps are two to three times higher. And this is without taking into account the costs of installation and drilling. The high cost of pumps of this type is due to the fact that, with their own small diameter, they must provide a high head. To solve such a difficult task, designers have to resort to complex technical solutions, for example, to create a multi-stage suction system, which naturally leads to an increase in the cost of the apparatus.

A well pump differs from a well pump in that it has an internal jacket for cooling the engine and therefore can be placed in a well or a large diameter well. Pumps of both types have the shape of a cylinder, but well pumps have a larger diameter than borehole pumps, and therefore more efficiently use the capabilities of the engine. Such pumps are distinguished by increased performance and lower cost with the same power consumption and head as in borehole pumps..

Unlike a well pump, the electric motor of a borehole pump is cooled by the flow of raised water. Therefore, for each borehole pump, the technical documentation must indicate the minimum permissible speed of water movement. That is why when using borehole pumps, the diameter of the well is so important, which should not be much larger than the diameter of the pump..

How to choose the right borehole pump? There is a fairly simple formula by which you can roughly determine the required pump head:

Hrequire = Hdin + Hhouse + Hsap + 20%,

where Hreq is the required head, m; Hdin – dynamic water level, i.e. distance from the earth’s surface to the water level in the well after turning on the pump (usually the water level drops by 3-8 m when the pump is turned on), m; Hdoma – the distance from the surface of the earth to the upper mark of the rise of water in the house; Hsap – pressure providing pressure in the water supply system (usually 1-3 atm, i.e. 10-30 meters of water column), m.

20% is added to take into account the resistance in the pipeline. It is clear that this figure is approximate and strongly depends on the distance from the house to the well. Let’s consider the choice of a pump using a simple example. Suppose the following conditions are set: the required water supply is 2 m ^ 3 h, the dynamic water level is 61 m, and the highest point of the water intake is on the third floor (floor height is 3 m).

Then we get:

Hrequire = (61 + 6 + 30) x 1.2 = 116.4 m

Next, the characteristics of the pumps are taken and according to the graph linking the head and flow rate, the pump brand closest to the required parameters (flow rate 2 m ^ 3 h and head 116.4 m) is selected.

The scope of application of the borehole pump significantly expands the possibility of its horizontal installation. In cases where water is taken from a lake or river, which are at a considerable distance from the house, and a large pressure is required, a borehole pump can be used by placing it in a cooling jacket..

In addition, the pump must be fixed along the axis of the casing, and in no case touch its walls, since in this case the cooling of the electric motor will be disturbed. A very large number of good European pumps of various capacities and sizes are offered on the Russian market. There are pumps of small diameter equal to 3 “, and there are also 10”.

It is almost always possible to choose a pump that will provide the optimal amount of water for you, because the nominal performance of borehole pumps ranges from one to 200 or more cubic meters of water per hour.

A good borehole pump is a technically complex and, as a consequence, a rather “capricious” device. He is ready to provide excellent work, but also requires careful attitude towards himself. For its normal operation, a stable voltage is required in the mains. The maximum voltage tolerance declared by most manufacturers is ± 5%.

In the description of the pumping stations, it was already mentioned about the need to install a check valve. It is also required when using borehole pumps so that water does not go back into the well when the pump is turned off.

It should be noted that both for pumping stations and for borehole pumps their protection against “dry running” is very important. “Dry running” occurs in a situation when the water level in the well or well falls below the critical level and the suction pipe (hose) is above this level. As a result, the engine overheats and the pump fails. To avoid this, there are several ways to protect the pump. A float system can be used. The scheme of work in this case is quite simple. When the water level falls, the float drops with it, opens the power supply circuit and turns off the pump. When the water level rises to the normal value, the float will rise again and, having closed the line, turns on the pump.

The pump protection works in a similar way by means of two special electrodes (level sensors) lowered into the water, connected to a protective device. If the lower electrode is above the water level, then the pump turns off, and vice versa, when the water reaches the level of the upper electrode, the protective device will turn on the pump.

Another way to protect the pump from dry running is to use a device that does not monitor the water level in the well or well, but the passage of water through the pump. There is water – the pump works, as soon as the movement of water stops, the device stops its operation.

There are situations when it is required to raise water from a well with a permanent or temporary power outage. It’s good if you have a generator, but if not? To solve this problem, consider another type of pump.

Submersible drainage pumps

Unfortunately, it is not so rare in the spring, after the winter snow melts, and in the fall, during heavy rains, the basement or cellar of a country house is partially flooded. An indispensable assistant in this case is the drainage pump. Household drainage pumps are lightweight (from 4 kg) and consume very little electricity (from 0.3 kW). Such a small and, which is very important, quite inexpensive device, is capable of pumping out about 5 cubic meters of water per hour from a depth of up to 4 m.

Quite often, together with the groundwater, a lot of silt and dirt gets into the basement. For labor-intensive measures to clean the premises from such deposits, the optimal choice is a drainage pump model, which, in addition to pumping out water, can also take care of cleaning the bottom of the flooded room. The operation of such a pump is structured as follows. Part of the water pumped out by the pump is thrown back under pressure. As a result of the resulting impact, delamination and separation of the sediment from the bottom occurs. The resulting mixture of water and dirt is sucked in again by the pump and removed from the room. True, as far as I know, such pumps are produced only by the German company WILO.

Often household drainage pumps are already equipped with a float to turn on the pump depending on the water level. The float switch will give a signal to turn on the pump in case of filling the basement with water and will turn off the pump after all the water has been pumped out, which simultaneously protects the pump from running on “dry running”.