Understanding Pump Head and Shut-off Head: Simplified Guide

One of the trickiest aspects of understanding pumps is the idea of "head." While related to pressure, what exactly does it mean? Let’s break down this concept and make sense of why it matters for pump performance.

This guide will help you grasp “head” in a way that sticks, so you’ll always know what it is, how it connects to pressure, and why it’s essential.

What Is Pump Head?

Picture this: if you connect a pipe vertically from the pump’s discharge, the pump's head is simply the maximum height the pump can push water up against gravity. Essentially, higher pressure means higher pumping height, resulting in a greater “head.” If the water level in the tank is higher, the pump can push water further up the pipe, thanks to the extra head from the liquid in the suction tank.

More practically, a pump’s "total head" is the difference between the liquid level in the suction tank and the maximum height water can reach in the discharge pipe. This total head is what you’ll need to focus on.

Why Liquid Level in the Tank Matters

The height of the liquid in your tank impacts the head—raising the liquid level increases the head, and lowering it decreases the head. However, since manufacturers can’t know your tank’s liquid level, they provide the pump’s “total head” instead, which is the height difference between the liquid level in the suction tank and the pump’s water column.

In technical terms, the relationship looks like this:

Ht = Hd + Hs

• Ht: Total Head

• Hd: Discharge Head

• Hs: Suction Head
  

This formula works even if the liquid level is below the pump. When the suction head is negative, the discharge head drops by that amount while maintaining the same total head.

What Is Shut-off Head?

In a setup where liquid rises through a vertical pipe until gravity halts its ascent, the pump reaches what’s known as the “shut-off head.” Here, flow stops because gravity matches the pump’s force. The shut-off head is the head achieved at zero flow rate.

Matching Your Pump’s Performance with Your Needs

To select a pump, determine your required total head and flow rate. These two values interact closely—higher head (the shut-off head) occurs when flow rate is zero. When flow rate increases, friction within the pipes reduces the total head. This “friction head” loss means that as flow increases, total head decreases.

In systems with flow, total head equals discharge head minus suction head, adding friction head loss. The relationship between head and flow rate creates the pump’s performance curve, which is plotted to help select the right pump.

When choosing a pump, look for the point on the curve where your required head and flow rate intersect. This intersection will show if the pump can deliver enough head at the needed flow.

Why Use Head, Not Pressure?

Historically, pumps were often used to lift water uphill to storage tanks. If water needs to reach a height of 60 meters, using head (in meters) makes sense—you know you need at least 60 meters of head. Another reason for using head is that with liquids of similar viscosity to water, head remains the same across liquids, whereas pressure varies. This is why pumps are typically rated by head instead of pressure.

Need Help?

We hope this guide has clarified pump head! For more tips, check out our blog for more articles.

VertoPumps offers a vast range of pumps and spares, serving industries from mining to manufacturing. Our pump engineers are ready to help you select the right pump for your specific application, ensuring greater efficiency, productivity, and reduced downtime. Contact us to speak with one of our experts!