How does a deep well pump work?

Deep well pumps are mostly modular and consist of two main components: motor and hydraulic part (pressure stage). The electric motor is usually located at the lower end of the deep well pumps and converts the electrical energy supplied into a mechanical rotary movement. This rotation drives the hydraulic pump shaft via a clutch.

The hydraulics of modern deep well pumps usually consist of individual impellers and diffusers that are connected to each other via a pump shaft. The inflowing water is accelerated by the rapid rotary movement of the motor in the first impeller and transported to the next impeller by the centrifugal force with the help of the diffuser.

Each step increases the discharge pressure of the pumped medium, which makes it possible to efficiently pump water from great depths with this technology.

For example, the maximum suction height of suction pumps is physically limited to 10 meters (geodesic suction height).

Does a 3-inch or 4-inch deep well pump make sense for my fountain?

4-inch deep well pumps are ideal for wells with a diameter of at least 100mm and have clear advantages over 3-inch models.

Wells are often drilled with a diameter of only 80mm for cost reasons. In this case, there is only the choice of a 3-inch pump including the associated disadvantages such as lower delivery rates with higher power consumption. Pumps with a diameter of 3 inches should therefore only be used if the well has a smaller inner diameter than 100mm. In order to compensate for this disadvantage, some manufacturers rely on increasing the speed, which increases the pump performance but reduces the service life of the hydraulics. Abrasives such as sand, for example, have a much more aggressive effect on the wheels at higher speeds and wear them out faster.You should need a well pressure tank. So before you buy you should read the well water pressure tank reviews

What performance should my deep well pump have?

For the performance of a deep well pump, two characteristics are decisive, which are specified by the hydraulic part of the pumps:

  • The maximum delivery rate
  • The maximum pressure or delivery head

A suitable motor is required to achieve the specified values. It does not matter whether the motor is operated as 1-phase or 3-phase, as long as motor power (kW) and torque (daN) fit.

The higher the water to be pumped, the lower the delivery rate and the working pressure. The height that must be overcome when pumping is therefore one of the important criteria for choosing the right deep well pump.

How much pressure does my deep well blow require?

The pressure specified in bar is equivalent to the maximum delivery head. The pressure of a deep well pump is reduced by 1 bar per 10 meter head.

A pump with a maximum delivery height of 50 meters therefore has a working pressure of 5.0 bar. However, if this pump has to overcome a height of 30 meters up to the withdrawal point, the working pressure remaining at the water outlet opening is only 2 bar. 

What performance should my deep well pump have?

Normally a 4 inch deep well pump has a delivery rate that is about twice as high as a self-priming centrifugal pump of the same motor size. The decisive performance parameters of the pump are:

  1. The engine power in KW
  2. The conveying capacity in m³ per hour or liters per minute
  3. The maximum pressure in bar (per bar corresponds to the 10 m pump height) that a pump can generate

How much power does a pump need if it is to be used as a house or garden water supply system?

There are a few important factors to consider when answering this question:

The first step is to determine the corresponding minimum water pressure, which the pump must set up to implement the desired application. An example can be used to show which simple calculation steps are required for this.

If the water level in the pipe of the well is at a depth of 10 meters and the water on the second floor of a house (that is approximately 6 meters above ground level) is to be pumped with a maximum pressure at the water outlet of 4 bar, then the total head is (6 meters + 10 meters,) that is a total of 16 meters. This delivery head is divided by 10, which results in a pressure loss solely due to the height of 1.6 bar to be overcome. In addition, in practice there is an additional pressure loss of approx. 30% of 1.6 bar (= approx. 0.5 bar) due to bends, friction on the pipe, etc.

In total, the pressure loss in this example is approximately 2.1 bar (1.6 bar + 0.5 bar). At the upper head of the pump depth in the well, approx. 6.1 bar pressure must be built up to achieve 4 bar pressure at the highest tap on the 2nd floor. For comparison: The public domestic water supply network in Germany has a pressure of 4 to 6 bar.

However, it is not recommended that pumps always have to work up to their maximum pressure in the long term. The best efficiency is achieved when the pressure required is around 70-80% percent of the maximum pressure. For our calculation example, this means that we add another 20% to the 6.1 bar and then come to about 7.5 bar.

The result is clear: The ideal pump for this application should be able to build up a maximum pressure of approx. 7.5 bar.

The next point is the flow rate: A garden faucet, which receives its water from the public water network, delivers between 2,000l and 3500l water per hour depending on the distance to the main connection of the house and the pipe thickness. Garden irrigation requires, depending on the sprinkler model, between 300 and 1500 liters per hour.

Each deep well pump has a diagram that shows how many liters of water are delivered per hour at a certain head.

Caution: This delivery rate from the diagram is only correct if the pipe from the pump to the tap is not constricted and the diameter of the delivery pipe is the same thickness as at the water outlet of the pump. If a 1 inch pipe is used to transport water from the pump to the tap, but the pump has a 1 1/4 inch connection, the values in the diagram are no longer correct and the pump will not fully achieve the values in the diagram.

How can the pressure of the pump be regulated?

If the well pump only works with the water outlet always open, you do not need any pressure control. In this case, the pump is only operated via an on and off switch.

If the pump should always switch on automatically as soon as a tap is opened and stop automatically as soon as it is closed again, this is referred to as an automatic water supply system. This requires some additional components, but at least one electronic pressure switch.

Which is better, a mechanical pressure switch or a press control (electronic pressure switch)?

Mechanical pressure switches have proven themselves in a wide variety of pump systems for many years. This type of switch is switched via a spring-loaded rocker and conducts electricity to the pump via two poles, but only if the pressure falls below a previously set minimum pressure. To change the pressures, the spring tension is changed using a wrench and thus the pressure is also changed. In practice, this can mean that the pump is switched on as soon as the pressure drops below 3 bar and is switched off again when the pressure rises to, for example, over 4 bar.

When installing a mechanical pressure switch, it also makes sense to install a pressure indicator, also called a pressure gauge. This makes the pressures visible and can be changed easily.

For some years now, electronic pressure switches (press control) have been installed more and more in small, simple systems. These switches have the advantage that the pumps are automatically switched off as soon as water is no longer pumped. This prevents the pump from running dry when there is a lack of water. Such a switch can be particularly useful for wells that only have a limited amount of water.

However, these pressure switches are not adjustable and always switch the pump on permanently at 1.5 bar or 2.2 bar depending on the make. If the sensor does not register any flow for several seconds, the pump is switched off. In this case the pump has reached its maximum pressure. Thus, the pump is forced to run to its maximum pressure with each pump cycle before it is stopped by the pressure switch.

Please note: The electronic pressure switches cannot be adjusted and are also not suitable for high pressure pumps above 6 bar at the water outlet!

If, for example, a pump reaches a maximum pressure of 10 bar, the electronic switch will only switch it off at 10 bar. Hardly any moving part in a water system can withstand this extremely high pressure. This means that high pressure pumps should definitely be limited by a mechanical pressure switch at a maximum of approx. 6 bar. An electronic pressure switch is not suitable for this.