How to Choose the Right Water Pump for Your Home, Farm or Irrigation System

Choosing a water pump is not simply a matter of picking the biggest pump or the one with the highest flow rate.

The right pump depends on where the water is coming from, how much water you need, how much pressure is required, the distance and elevation the water needs to travel, and what the pump will be supplying.

A pump that works well for a small household water system may be completely unsuitable for irrigation, while a pump selected for a large irrigation system may be unnecessarily expensive and inefficient for a home.

At WTS, we supply a range of pumps for homes, lifestyle properties, farms, water storage and irrigation systems throughout New Zealand.

Start with the application

Before choosing a pump, consider what you actually need it to do.

Common applications include:

• Supplying water from a rainwater tank
• Providing household water pressure
• Boosting an existing water supply
• Moving water between tanks
• Supplying garden irrigation
• Supplying larger irrigation systems
• Drawing water from a bore or other water source
• Removing stormwater or grey water
• Pumping effluent or wastewater

Different applications require different pump types.

What determines the right pump?

There are several important factors to consider.

1. Water source

Where the pump is drawing water from makes a significant difference.

The source might be:

• A rainwater tank
• A storage tank
• A shallow well
• A bore
• A dam or pond
• A mains or trickle-feed supply
• A sump or drainage area

A surface-mounted self-priming pump may be appropriate for some shallow sources, while a submersible pump may be a better solution where the pump needs to operate within the water source.

2. Required flow

Flow is the amount of water the pump needs to deliver, usually measured in litres per minute (L/min).

For a household, the required flow depends on factors such as:

• Number of bathrooms
• Number of taps and outlets
• Showers and appliances
• Whether multiple outlets may operate at the same time

For irrigation, flow is determined by the irrigation zones and the equipment operating within each zone.

For example, an irrigation system may require a substantially higher flow than a typical household water supply.

3. Required pressure

Flow and pressure are not the same thing.

A pump needs to deliver the required flow at the required pressure.

This is particularly important for irrigation systems, where sprinklers or other irrigation equipment may require a specific operating pressure to achieve the correct flow and distribution.

For household systems, pressure also needs to account for the pressure required at the fixtures and any losses through pipework, filters and fittings.

4. Total head

Pump performance is often expressed in metres of head.

The total head requirement can include:

• Vertical lift
• Required pressure at the outlet
• Pipe friction losses
• Fittings and valves
• Filters
• Irrigation equipment
• Other system losses

This is why a pump advertised as having a maximum head of, for example, 50 metres does not necessarily deliver 50 metres of head at the flow rate you require.

The pump needs to be selected from its performance curve at the actual operating point.

Common types of water pumps

Pressure and domestic water pumps

For homes and lifestyle properties, the pump usually needs to provide reliable automatic water pressure whenever a tap, shower or appliance is used.

The Bianco NXT ECJetCore is one example of a domestic pressure solution in the WTS range. It combines a self-priming jet pump with an NXT Core electronic controller and is designed for applications including household water supply, garden irrigation, water transfer and pressure boosting.

The range includes several pump sizes, allowing the system to be selected according to the required performance rather than using one pump for every application.

Variable-speed pressure systems

Where consistent pressure and efficient operation are priorities, a variable-speed system can provide a more sophisticated solution.

The Davey EvoDrive and DAB Esy.Box are variable-speed home pressure systems designed to adjust pump operation according to demand.

Variable-speed systems can be particularly useful where water demand varies significantly throughout the day.

They can also be worth considering for larger homes or systems where maintaining stable pressure is important.

Multistage pumps

Multistage pumps use multiple impellers to develop higher pressure efficiently.

They can be useful for:

• Larger homes
• Rural water supplies
• Irrigation
• Pressure boosting
• Longer pipe runs
• Applications requiring higher pressure

The WTS range includes several multistage options, including:

DAB K Series

The DAB K Series provides a range of centrifugal pumps suitable for applications where higher flow and pressure performance is required.

Davies DMI Series

The Davies DMI Series is a 316 stainless steel horizontal multistage pump range. The stainless-steel construction makes this range particularly useful where durability and water compatibility are important considerations.

Bianco BLC Series

The Bianco BLC Series provides another stainless-steel multistage option across a range of applications.

The correct model within any of these ranges should be selected according to the required duty point rather than simply choosing the largest available model.

Self-priming jet pumps

Self-priming jet pumps can be useful where the pump is installed above the water source and needs to draw water into the pump.

They are commonly used for:

• Water tanks
• Shallow wells
• Domestic water supply
• Garden irrigation
• Water transfer

Options include the  Trevoli BJZ Series and DAB JETCOM Series.

These provide different performance options, so the correct model can be selected according to the required flow and pressure.

Submersible water pumps

Submersible pumps operate within the water source.

They can be particularly useful for:

• Water tanks
• Wells and bores
• Water transfer
• Pressure systems
• Drainage
• Other applications where the pump needs to operate underwater

The WTS range includes several types of submersible pump.

DAB Divertron

The DAB Divertron 900 is an electronic submersible pump designed for applications where automatic water supply and pressure are required from a tank or other water source.

DAB ESYDIVER

For more demanding applications, the DAB ESYDIVER range combines a submersible multistage pump with integrated electronic control and inverter technology.

This type of system can provide an alternative to a conventional surface-mounted pressure pump arrangement.

Trevoli Subtron-50

The Trevoli Subtron-50 provides another submersible pressure pump option for suitable water supply applications.

Trevoli MVH-10A

The Trevoli MVH-10A is a high-head submersible pump suited to applications where a submersible installation and higher head performance are required.

Drainage, grey water and wastewater pumps

Not every pump is designed to supply clean water.

Drainage and wastewater applications require pumps specifically designed for the type of water and solids involved.

The WTS range includes:

Bianco B42a

The Bianco B42a is a high-head submersible pump designed for clean or slightly dirty water and is suitable for applications such as drainage and dewatering.

Davey D42A/B

The Davey D42A/B is a high-head drainage pump designed for moving water where greater pumping head is required.

Davey Vortex pumps

Davey's submersible vortex pumps are suited to grey water and effluent applications where the water may contain suspended solids.

Bianco B120GS2 Grinder Pump

Where wastewater contains soft solids that need to be broken down before pumping, a grinder pump may be appropriate.

The Bianco B120GS2 is specifically designed for sewage and wastewater applications and incorporates a grinder/cutter system.

A wastewater pump should never be selected simply because it has the required flow and head. The type and size of solids, discharge arrangement and intended application all need to be considered.

Pumps for irrigation

Irrigation is one area where correct pump selection is particularly important.

It is tempting to choose a pump based on the advertised maximum flow or maximum head, but these figures alone do not tell you how the pump will perform in the completed irrigation system.

The pump needs to deliver the required flow at the required operating pressure after accounting for the hydraulic losses in the system.

These can include:

• Mainline pipe friction
• Lateral pipe losses
• Valves
• Filters
• Fittings
• Elevation changes
• Sprinklers
• Other irrigation equipment

For smaller irrigation systems, pumps such as the Bianco BLC, Davies DMI or suitable DAB K Series models may provide appropriate options depending on the calculated duty.

For larger or more complex irrigation systems, WTS recommends designing the system around the required duty point rather than selecting a pump from a catalogue specification alone.

Our irrigation designs use hydraulic calculations to determine the required flow, pressure, pipe sizing and pump duty so that the complete system works together.

Don't choose a pump based on horsepower alone

Pump horsepower or kilowatt rating is useful when comparing equipment, but it should not be the starting point for pump selection.

Two pumps with similar motor sizes can have very different performance characteristics.

Likewise, a larger motor does not automatically mean a better pump for your application.

The important question is:

Can the pump deliver the required flow at the required pressure for the actual system?

That is why pump curves and the complete hydraulic system need to be considered.

What happens if the pump is too small?

An undersized pump may result in:

• Low water pressure
• Insufficient flow
• Poor irrigation coverage
• Sprinklers failing to operate correctly
• Excessive pump running
• Poor household water performance

The pump may simply be unable to meet the system demand.

What happens if the pump is too large?

Oversizing a pump can also cause problems.

An oversized pump may:

• Use more electricity than necessary
• Operate outside its ideal performance range
• Cause excessive pressure
• Increase system wear
• Require additional pressure regulation
• Increase the initial cost of the system

The objective is not to install the biggest pump possible.

The objective is to select the right pump for the duty.

Think about the whole system

A pump does not operate in isolation.

The pump, pipework, filters, valves, storage and end-use equipment all affect the final result.

For example, increasing the pump size without considering the pipework may simply increase pressure losses or create other problems further through the system.

Likewise, installing a high-performance pump on a system with inadequate water storage may not solve the underlying problem.

For irrigation, the sprinklers, zones, pipework, storage and pump should all be considered together.

For a household water system, the same principle applies to the tank, pump, filters, pressure controls and plumbing.

When should you ask for professional pump selection?

Professional pump selection is particularly worthwhile when:

• The property has significant elevation changes
• The pipe runs are long
• Several outlets need to operate simultaneously
• The pump will supply irrigation
• The system is supplying a large home or multiple buildings
• You are pumping from a bore
• The water source has a limited yield
• The system includes filtration
• You are planning future expansion
• The pump is part of a larger commercial or rural water system

In these situations, selecting a pump from a simple flow or horsepower specification can result in an unsuitable system.

WTS pump supply and system design

At WTS, we look at the complete water system rather than treating the pump as an isolated component.

We can assist with:

• Pump selection
• Pump sizing
• Water storage
• Pressure systems
• Filtration
• Irrigation design
• Hydraulic calculations
• Pump installation
• System upgrades
• Pump servicing and maintenance

Our pump range includes domestic pressure pumps, multistage pumps, jet pumps, submersible pumps, drainage pumps and specialist wastewater pumps.

For more complex water supply and irrigation projects, we can design the system around the actual site requirements, including flow, pressure, elevation, pipework and future demand.

Need help choosing a pump?

If you already know your required flow and pressure, you can browse the WTS pump range online.

If you're not sure what pump you need, contact the WTS Team with as much information as you have about your water source, pipework, elevation, intended use and required outlets.

For irrigation and larger water systems, we can help determine the required pump duty and select equipment to suit the complete system.

Choose the pump for the system, not the system for the pump.