Category: Pumps

What is a Submersible Pump?

A submersible pump (or electric submersible pump (ESP) is a device which has a hermetically sealed motor close-coupled to the pump body.

The whole assembly is submerged in the fluid to be pumped.

The main advantage of this type of pump is that it prevents pump cavitation, a problem associated with a high elevation difference between pump and the fluid surface.

Submersible pumps push water to the surface as opposed to jet pumps having to pull water. Submersibles are more efficient than jet pumps.

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What is a Centrifugal Pump?

A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure of a fluid. Centrifugal pumps are commonly used to move liquids through a piping system.

The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from where it exits into the downstream piping system.

Centrifugal pumps are used for large discharge through smaller heads.

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We are not going to cover all aspects of the South African Water legislation in this article, we are only going to look at some fundamental principles, which might affect the local borehole user, as well as other farming activities.

Ownership of water

In the preamble to the National Water Act it is recognised that water is a scarce and unevenly distributed national resource, which occurs in many different forms and are all part of a unitary, inter-dependant hydrological cycle, whereas previously groundwater and surface water were treated differently. As such the National Water Act states that there will be no ownership of water (surface and groundwater), only a right to use for basic human needs and the environment. The volume, quality and sustainability of water necessary to sustain human life, and ecological functions on which human life depends, will be reserved in such a manner that the long-term sustainability is not jeopardized.

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There are a number of aspects that needs to be taken into consideration when testing a borehole. According to Prof van Tonder at the Institute for Groundwater Studies (Free State University) there are two important rules that needs to be kept in mind when determining the sustainable yield I.e.: The total abstraction from a borehole should be less than the natural groundwater recharge, and secondly, a borehole should be pumped in such a manner that the water level never reaches the position of the main water strike (normally associated with a fracture). Should this happen the yield will inevitably be affected and the borehole would eventually dry up.

Specific information is required to properly test a borehole; these can be listed as follows:

What is the rest water level before the start of the test?

How does the water level change over time once pumping has started?

How long does it take for the water level to recover after the pump has been stopped to recover to the original level – or how far does the water level recover after the same amount of time allowed as for pumping – leaving a residual drawdown?

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How to go about getting your own private water supply…

Firstly is the site suitable for a borehole is there enough space away from possible contaminants such as cess-pits, roads and other dwellings or industries. The next stage is to obtain consent to drill from the environment agency for water abstraction. A test borehole needs to be drilled to establish water quality, the depth of the water surface and the volume of water in the well. Additionally the borehole is lined with a casing and a pump selected and fitted possibly with water treatment if required.

Finding a suitable borehole well location

There are many scientifically proven techniques to best locate a position for the drilling of a borehole. Much controversy exist in the ground water industry over  which method is the best, although not one single method currently exist that can, with 100% accuracy, indicate the exact depths and volumes of ground water occurrence.

There is however scientific methods that can, with the correct application, increase the chances for successfully locating borehole sites. The following factors are taken into consideration in ground water exploration. Firstly one has look at the geological setting of the area I.e. the types of geological formations present in an area, as well as the potential of these formations to act as aquifers. Secondly one has to look at hydrological factors such as rainfall and the percentage that contributes to groundwater recharge, as well as the water balance for a specific catchment area.

Typical questions that are asked in a groundwater investigation are: how much do we need? Can the aquifers provide in this need?, is the ground water quality suitable for the intended use? Etc. To answer such questions it is necessary to study available information such as geological and hydrogeological maps, aerial photographs, satellite images, borehole information, such as borehole depths, yields, depths at which water was intersected, water quality intersected, of all, or as many as possible of the boreholes in the area.

We list five of the most commonly used geophysical methods applied to identify positions for borehole drilling. The essence of these techniques is based on the understanding of the geological sequences present in the area, and none of these techniques can be used in isolation.

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What is a Borehole Pump?

A borehole pump is used to extract water from a borehole. Boreholes are narrow shafts drilled vertically into the ground. The holes are made using a drilling rig that creates a borehole with specific dimensions so that the borehole pump can fit through with very little clearance on all sides.

How does a Borehole Pump work?

Because borehole pumps come into direct contact with minerals in the soil, they are typically made of corrosion resistant materials. Borehole pumps consist of two main components: a foot part that houses the pumping mechanism and makes contact with the water that is to be pumped; and the head part, which serves as the weight-bearing portion and the outlet for the water

Where are Borehole Pumps used?

Borehole pumps are used in a variety of fields including irrigation, municipal water supply, construction, mining, and industry.