UNDERSTANDING A PUMP CURVE

Example Curves How to red a pump curve 0525

A pump curve, or performance curve, is a graph that shows how a pump’s flow rate changes with pressure (head). It helps you understand how a pump will perform under different conditions so you can choose one that suits your system.

The curve usually starts high on the left, where the pump produces high pressure at low flow and slopes downward to the right, where flow increases but pressure drops. This is because a pump generates more pressure when moving less water, but as flow increases, pressure naturally decreases.

Different pumps are designed with specific flow and pressure capabilities to suit various needs, from industrial use to home and lifestyle applications.

Below are simple explanations of the key parts of a pump curve graph:

Flow Rate (horizontal X-axis):

Measured in litres per minute (L/min) or cubic metres per hour (m³/h).
Can be marked as ‘Q’ on the graph.
As you move to the right, the flow rate increases.
Flow rate tells you how much water the pump is moving over time.

Head (vertical Y-axis):

Measured in metres (m).
Head shows the pressure the pump can create, or how high it can push water.
Think of it like holding up a garden hose the higher you lift it; the more pressure you need to get water to the top.
As you move upwards, the pressure (head) increases.

Best Efficiency Point (BEP):

This is the sweet spot where the pump runs most efficiently.
At the BEP, the pump gives the best performance while using the least energy.
It’s usually around the middle of the curve.
Running a pump near its BEP means less wear, lower costs, and better results.

Pumps

Old pressure tank safety for NZ farms

Many farms and rural properties across New Zealand still rely on old steel water pressure tanks with no internal bladder. While these tanks may appear to work normally, they often corrode internally and can fail suddenly. Consequently, such failures put people, livestock, and property at serious risk. Understanding old pressure tank safety, recognizing warning signs, and switching to safer alternatives is essential for protecting your farm and rural water system.

What is a non-bladder water pressure tank?

Older steel tanks store water and compressed air in the same chamber. The air provides pressure to move water through the system. Over time, constant water contact corrodes the steel, thinning and weakening the tank walls.
Since this corrosion occurs inside the tank, you often cannot see it from the outside. Even if a tank seems to work normally, it may already be at risk of sudden failure. Farmers commonly installed non-bladder tanks decades ago, and many remain in pump sheds, dairy sheds, and rural homes today.

How internal corrosion develops

Corrosion forms because the steel is constantly exposed to water. In addition, fluctuations in temperature and pressure accelerate metal weakening. Therefore, tanks that appear fine externally may be dangerously compromised internally.

Real-life example: sudden tank failure

A recent incident involved an old steel pressure tank exploding without warning. The explosion tore off a pump shed roof, damaged walls and equipment, cut power lines, and hurled the tank several metres. Fortunately, no one was injured.
This incident demonstrates how dangerous older water pressure tanks can be. In particular, on farms where tanks are located near livestock or machinery, sudden failure can result in serious injuries and property damage. Maintaining farm water pressure tank safety is therefore critical.

Why modern bladder-type tanks are safer

Modern bladder-type tanks separate water from the compressed air using an internal bladder or diaphragm. This design prevents water from contacting the steel, reducing corrosion and extending tank life.

Benefits of bladder-type tanks

Reduces the risk of internal rust and corrosion
Maintains consistent water pressure for pumps
Lasts longer than old steel tanks
Complies with modern NZ safety standards

Replacing an old non-bladder tank with a bladder-type tank is safer, more reliable, and more cost-effective than risking sudden failure.

Regular inspections improve farm safety

On New Zealand farms, tanks are often installed in pump sheds, dairy sheds, or near living areas. Therefore, safety must be a priority. Even if a tank looks fine externally, internal corrosion can make it unsafe.

Farmers should inspect tanks regularly. Watch for rust, leaks, unusual noises, or pressure issues. In addition, for tanks older than 15 years, consider hiring a professional to assess their condition. WorkSafe NZ recommends proactive management of pressurised equipment to prevent accidents and costly damage.

When to replace a water pressure tank

You should replace a tank if:

It is 15 years old or older
It has no internal bladder
The tank’s age or type is unknown
It is located in a pump shed, dairy shed, or near living areas

A professional inspection can determine whether a tank remains safe or requires immediate replacement. As a result, you can prevent sudden failures and serious incidents.

Safer solutions for your farm

The safest option is a modern bladder-type water pressure tank, available in sizes from 80 L to 450 L for farms and rural properties. Even if a tank shows no external damage, hidden corrosion can make it unsafe. Therefore, early replacement prevents sudden failure and serious accidents.

Protect your farm and water system

Old water pressure tanks are a hidden hazard on many New Zealand farms and lifestyle blocks. Timely inspection and replacement protect people, livestock, and property, while ensuring old pressure tank safety.

If you are unsure about your tank’s condition, have it professionally checked or replaced before a failure occurs. In addition, educating your team about the risks of old steel tanks improves overall farm safety.

Pumps

Catalogues

SOCO Limited
+64 6 354 3651 or +64 9 415 8181
sales@soco.co.nz

471 Tremaine Avenue
Palmerston North 4412
New Zealand