Water pumps and their controls are central to effective water supply systems, particularly in Kenya where reliable water delivery supports domestic, commercial, and agricultural activities. Installing these components requires precise knowledge of the equipment, tools, and technical terms to ensure systems operate efficiently and sustainably. Plumbing professionals must understand these elements to meet regulatory standards and client expectations while maintaining safety and functionality. This chapter explores the essential tools and equipment used in pump installation and clarifies key terms and concepts relevant to water pump systems.

2.1 Terms and concepts

Understanding the terminology and fundamental concepts related to water pumps and their controls is critical for plumbing professionals working in Kenya. These terms form the foundation for effective communication, accurate installation, and troubleshooting within diverse water supply contexts such as county water projects, agricultural irrigation, and commercial plumbing systems.

Definition of a Water Pump

A water pump is a mechanical device that adds energy to water so that the water can be moved from one point to another, raised to a higher level, or delivered at a higher pressure than it had at the source.

The phrase that matters in that definition is adds energy. A pump does not create water and it does not create pressure out of nothing. It takes energy from a driver, which may be an electric motor, a diesel engine, a solar array or a human arm on a hand lever, and transfers that energy to the water passing through it. Everything else in this unit follows from that one idea: if you know how much energy the water needs, you know what size of pump to fit.

Water entering a pump arrives at the suction side and leaves at the delivery side, also called the discharge side. The energy the pump must supply covers two things:

1. Lifting the water through a vertical height, which is the static lift.
2. Pushing the water through pipes, bends, valves and fittings, which resist flow and cause friction losses.

Parts Common to All Water Pumps

Whatever the type, every water pump has the same four elements, and naming them correctly is the basis of fault reporting on site.

• Prime mover: the driver that supplies the energy, such as an electric motor, diesel engine or solar powered motor.
• Casing: the body that contains the water and directs it from the suction side to the delivery side.
• Moving element: the part that acts on the water. In a centrifugal pump this is an impeller. In a reciprocating pump it is a piston or plunger.
• Suction and delivery connections: the inlet through which water enters and the outlet through which it leaves.

Related Terms Used Throughout This Unit

• Priming: filling the pump casing and suction line with water before starting, so that no air remains. Most surface pumps cannot draw water while air is trapped inside them.
• Prime: the state of being full of water and ready to pump. A pump that has lost its prime is full of air and will run without delivering water.
• Dry running: operating a pump with no water passing through it. This destroys seals and bearings within minutes and is the most common cause of avoidable pump failure on Kenyan sites.
• Duty: the flow rate and head a pump is required to deliver in a particular installation, written for example as 2.5 litres per second against 59 metres head.

How Water Pumps Are Classified

All water pumps fall into two families, and every type named later in this topic belongs to one of them.

Note the relationship between the two terms, because they are often confused. Reciprocating is not a separate family standing alongside positive displacement. A reciprocating pump is one kind of positive displacement pump, the kind that uses a piston or plunger moving back and forth.

2.1.1 Pump Types and Their Characteristics

Water pumps vary in design and application, and knowing the types helps plumbers select the right pump for specific water supply needs. The types met most often in Kenyan plumbing work are centrifugal, submersible, jet, and positive displacement pumps including the reciprocating kind, each with distinct operating principles and suitable environments.

Centrifugal Pumps

Centrifugal pumps operate by converting rotational energy from a motor to kinetic energy in water, creating flow through centrifugal force. They are widely used in municipal water supply systems due to their efficiency in moving large volumes of water at low viscosity. For instance, county water offices often deploy these pumps for borehole water extraction and distribution.

Submersible Pumps

Submersible pumps are designed to operate underwater, typically in wells or boreholes. Their sealed motor and pump unit prevent water ingress, making them ideal for deep well water extraction in rural farms and small-scale irrigation schemes. These pumps reduce noise and avoid cavitation issues common in surface pumps.

Note that submersible describes where the pump sits rather than how it works. Most borehole submersibles are multistage centrifugal pumps that happen to be built for underwater duty.

Positive Displacement Pumps

Positive displacement pumps move water by trapping a fixed volume and forcing it through the discharge pipe. They are suitable for applications requiring precise flow rates and high pressure, such as chemical dosing in water treatment plants. SACCO-managed water kiosks sometimes use these pumps to ensure measured water delivery.

Jet Pumps

Jet pumps use a combination of centrifugal force and a jet of water to create suction. They are often used for shallow wells and household water supply in peri-urban areas. Hotels in Nakuru, for example, install jet pumps to boost water pressure for guest rooms.

Factors in Selecting a Pump

Before comparing individual types, five practical factors narrow the choice on any job.

• Efficiency varies, with centrifugal pumps generally more efficient for high flow rates.
• Installation depth influences pump choice; submersible pumps suit deep wells.
• Maintenance needs differ; positive displacement pumps require more frequent servicing due to moving parts.
• Power source compatibility affects selection; electric motors are common, but diesel engines may be used in remote areas.
• Cost implications must be considered, balancing initial investment against operational expenses.

Characteristics of Each Pump Type

Each pump type possesses unique characteristics that influence its suitability for different applications in Kenya.

• Centrifugal Pumps: These pumps are highly efficient for moving large volumes of water at moderate pressure and are commonly used by Nairobi City Water and Sewerage Company for municipal water distribution. Their simple design allows for easy maintenance, but they are less effective for high-pressure, low-flow scenarios.

Centrifugal pumps installed in a mechanical room (Source: Wikimedia Commons)

• Submersible Pumps: Designed for operation while fully submerged, these pumps are ideal for deep boreholes in rural counties such as Kitui, where water tables are low. Their sealed construction prevents water ingress, reducing the risk of electrical faults and ensuring quiet operation, which is valued in hospitals and residential areas.

• Positive Displacement Pumps: These pumps deliver a consistent flow regardless of pressure changes, making them suitable for dosing chemicals in water treatment plants like those operated by Athi Water Services Board. However, they require more frequent maintenance due to their complex internal mechanisms.

Diagram of a positive displacement pump mechanism (Source: Wikimedia Commons)

• Jet Pumps: Jet pumps are effective for shallow wells and are often used in peri-urban developments around Kisumu. They combine the principles of centrifugal and ejector pumps, allowing them to lift water from moderate depths and boost household water pressure.

Diagram of a jet pump with adjusting screw (Source: Wikimedia Commons)

• Reciprocating Pumps: A reciprocating pump is the piston or plunger type of positive displacement pump. It is used when high pressure and precise flow control are needed, such as in industrial cleaning systems at manufacturing firms in Thika. Its robust construction allows it to handle viscous or particulate-laden fluids, but it generates pulsating flow, which may require additional dampening equipment.

Diagram of a reciprocating boiler feed pump (Source: Wikimedia Commons)

Dangers of Each Pump Type

While each pump type offers distinct advantages, they also present specific dangers if not properly selected, installed, or maintained in Kenyan contexts.

• Centrifugal Pumps: If operated at low flow rates, these pumps can overheat and suffer from cavitation, leading to impeller damage. In county water projects, improper sizing can result in frequent breakdowns and water supply interruptions.
• Submersible Pumps: Electrical insulation failure due to poor waterproofing can cause electric shocks or pump failure, especially in installations where quality control is lax. Retrieval for maintenance is difficult, increasing downtime in critical facilities like hospitals.
• Positive Displacement Pumps: Over-pressurization can occur if discharge valves are closed during operation, potentially bursting pipes or damaging pump components. This is a risk in automated dosing systems at water treatment plants.
• Jet Pumps: These pumps are sensitive to air leaks in suction lines, which can cause loss of prime and dry running, damaging the pump. In rural installations, poor pipe jointing can exacerbate this risk.
• Reciprocating Pumps: The pulsating flow can induce vibrations and fatigue in connected pipework, leading to leaks or joint failures. In industrial settings, inadequate maintenance can result in hazardous leaks of pumped fluids.

2.1.2 Pump Control Systems and Their Functions

Pump controls regulate operation to optimize performance, protect equipment, and conserve energy. Understanding these systems enables plumbers to install and configure controls correctly for varied water supply demands.

Pressure Switches

Pressure switches monitor system pressure and activate or deactivate pumps accordingly. They maintain desired water pressure in residential or commercial buildings, avoiding continuous pump operation and reducing wear.

Float Switches

Float switches detect water levels in tanks or reservoirs and control pump activation to prevent overflow or dry running. County water offices use float switches to automate water storage management in public facilities.

Variable Frequency Drives (VFDs)

VFDs adjust pump motor speed based on demand, improving energy efficiency and prolonging equipment life. In large water treatment plants, VFDs help manage fluctuating water consumption patterns effectively.

Timers and Programmable Logic Controllers (PLCs)

Timers schedule pump operation for specific periods, useful in irrigation systems to optimize water use. PLCs offer advanced control by integrating multiple sensors and automating complex sequences, employed in industrial water supply systems.

Alarms and Safety Devices

Alarms alert operators to abnormal conditions such as low pressure or motor overload. Safety devices prevent damage by shutting down pumps during faults, essential in hospitals and other critical institutions.

Functions of Pump Control Systems

Pump control systems serve several vital functions in Kenyan water supply installations:

• Automation of Operation: Controls enable pumps to start and stop automatically based on system demand, reducing the need for manual intervention in facilities such as Moi Teaching and Referral Hospital.
• Protection of Equipment: By monitoring parameters like pressure and water level, control systems prevent dry running, over-pressurization, and motor overload, which are common causes of pump failure in county water offices.
• Energy Conservation: Advanced controls like variable frequency drives adjust pump speed to match demand, lowering electricity consumption and operational costs.
• System Monitoring and Alerts: Controls provide real-time feedback and alarms for abnormal conditions, allowing for prompt corrective action in critical infrastructure like Jomo Kenyatta International Airport's water system.
• Integration with Building Management Systems: In large commercial buildings in Nairobi, pump controls are integrated with central management systems to coordinate water supply with other utilities, ensuring efficient resource use and rapid fault detection.

2.1.3 Hydraulic Concepts Relevant to Pump Installation

Knowledge of hydraulic principles is essential for designing and installing water pump systems that deliver required flow and pressure efficiently. These concepts include head, flow rate, and system losses.

Head

Head represents the height to which a pump can raise water, measured in meters. It combines static head (vertical distance) and dynamic losses due to pipe friction and fittings. Accurate head calculation ensures the selected pump meets system demands.

Total head = static lift + delivery height + friction losses

Flow Rate

Flow rate indicates the volume of water delivered per unit time, typically liters per second or cubic meters per hour. Plumbing professionals must match pump capacity to expected water usage in buildings or irrigation.

To convert between the two units in common use: litres per second × 3.6 = cubic metres per hour.

System Losses

Friction losses in pipes, valves, and fittings reduce effective head and flow rate. Selecting appropriate pipe sizes and materials minimizes losses, enhancing pump efficiency and reducing energy consumption.

Net Positive Suction Head (NPSH)

NPSH is the pressure required at the pump inlet to prevent cavitation, which can damage impellers. Proper system design maintains adequate NPSH, especially in deep well or booster pump applications.

Pump Curve Interpretation

Pump curves graphically represent the relationship between head and flow rate for a specific pump model. Understanding these curves allows plumbers to select pumps that operate near optimal efficiency points.

Worked Example: Sizing a Borehole Pump

A borehole at a secondary school in Machakos must supply a storage tank. The water level in the borehole stands 45 metres below ground. The tank inlet is 8 metres above ground. Friction losses in the rising main and fittings have been calculated as 6 metres. The school needs 2.5 litres per second.

Step 1. Find the total head.

Total head = 45 + 8 + 6 = 59 metres

Step 2. Convert the flow rate.

2.5 litres per second = 2.5 ÷ 1000 = 0.0025 cubic metres per second
2.5 × 3.6 = 9 cubic metres per hour
Running 8 hours a day gives 9 × 8 = 72 cubic metres per day

Step 3. Find the hydraulic power, which is the power actually delivered to the water.

Hydraulic power = density × gravity × flow rate × head
Hydraulic power = 1000 × 9.81 × 0.0025 × 59 = 1447 watts, or 1.45 kilowatts

Step 4. Allow for pump efficiency. Taking the pump as 65 per cent efficient:

Shaft power = 1447 ÷ 0.65 = 2226 watts, or 2.23 kilowatts

Step 5. Allow for motor efficiency. Taking the motor as 90 per cent efficient:

Electrical input = 2226 ÷ 0.90 = 2474 watts, or 2.47 kilowatts

Step 6. Select the motor. Pump motors are sold in standard sizes, so the next size above 2.47 kilowatts is selected. A 3 kilowatt motor is fitted.

Note how the figures grow at each step. The water itself needs only 1.45 kilowatts, yet a 3 kilowatt motor is installed. The difference is lost as heat in the pump and the motor, which is why efficiency figures must never be left out of a sizing calculation. A plumber who sizes the motor from the hydraulic power alone will fit a pump that cannot meet the duty.

2.1.4 Legal and Safety Terminology in Water Pump Installation

Compliance with Kenyan safety regulations and standards ensures installations are safe, durable, and legally acceptable. Knowing relevant terms and requirements is crucial for professional practice.

Occupational Safety and Health Act, 2007

The Occupational Safety and Health Act, 2007 is the Kenyan law governing safety at the workplace. It is enforced by the Directorate of Occupational Safety and Health Services, which sits under the Ministry of Labour. The Act covers safety requirements for electrical wiring, mechanical installation, and working at heights during pump installation. Adhering to these requirements protects workers and users.

Note that this is Kenyan law. The abbreviation OSHA is also the name of a United States agency, and the two are not the same body, so site documents should name the Act and the year in full.

Water Quality Standards

Pumps must not contaminate water; materials and installation practices must meet Kenya Bureau of Standards (KEBS) guidelines. This is particularly important in hospital water supply systems.

Electrical Safety Terms

Terms like grounding, circuit breakers, and overload protection relate to the electrical aspects of pump installation. Proper electrical installation prevents accidents and equipment damage.

Environmental Protection Terms

Understanding terms related to wastewater discharge and noise pollution ensures installations comply with National Environment Management Authority (NEMA) regulations.

Warranty and Certification

Terms regarding product warranties and certifications guide selection of pumps and components that meet quality and durability expectations.

Chapter Summary

This chapter introduced key terms and concepts essential for understanding water pump systems and their operations. It highlighted the specific tools and equipment required for effective installation and maintenance of pumps. The discussion on pump selection covered various types including lift pumps, submersible pumps, centrifugal pumps, booster pumps, and reciprocating pumps, explaining their distinct functions and suitability for different water supply scenarios. Detailed procedures for pump installation were provided, emphasizing correct positioning and secure fittings. Installation of pump controls was examined through components such as pressure switches, float switches, non-return valves, and foot valves, which regulate and protect the pump system. Functionality tests were outlined to ensure pumps operate efficiently and safely after installation. Finally, the importance of regular housekeeping was stressed to maintain pump performance and prolong equipment lifespan.