Pump head is the total resistance a pump has to overcome, measured in metres. It is not just how high the water is lifted. It is that lift plus the friction losses in the pipe and fittings, plus any pressure needed at the outlet. Get the head right and you can size a pump properly; underestimate it and the pump will disappoint.
Static head: the lift
Static head is the straightforward part: the vertical height from the water surface up to the discharge point. Pump water 5 metres up and you have 5 metres of static head before anything else is counted.
Friction head: the hidden part
Friction head is the resistance the water meets travelling through the pipe or hose, and it is the part people forget. Long runs, narrow bores, bends, valves and the wrong hose all add head that the pump must overcome. A long, thin or kinked hose can rob a pump of a surprising amount of performance, which is why hose length and diameter affect pump performance so much, and why the choice between layflat and suction and delivery hose matters.
A quick way to estimate friction
For 25 to 50 mm hose, the rule of thumb we use on the phone is this: every 10 metres of horizontal hose adds about 1 metre of head, every tight bend or elbow adds about 1 metre, and a non-return valve adds about 2 metres. It is approximate, and it gets less reliable with very long runs, small bores or high flows, but it will get you to the right size of pump.
A worked example
Say the water is in a cellar 2 metres below the garden, and it has to travel through 20 metres of 50 mm layflat hose with one elbow and a non-return valve. The static head is 2 metres. The friction allowance is 2 metres for the hose, 1 metre for the elbow and 2 metres for the valve, so the total head is about 7 metres. Read the pump's flow at 7 metres on its curve, not at its headline maximum. A pump quoted at 200 litres a minute may give nearer 120 at that head, and a pump with a maximum head of 11 metres will already be past the middle of its curve, which is where you want it to run.
Total head is what counts
Add the static lift and the friction losses (and any outlet pressure) together and you get total head, sometimes called total dynamic head. That is the figure you read the pump's flow against on its curve, at its operating point, not the pump's headline maximum, as explained in how to read a pump curve. As a rough guide, 10 metres of head is about 1 bar. Understanding both numbers together is covered in pump curves explained: flow rate and head.
Working out your total head
Measuring the lift is easy; estimating friction is where most people struggle. Our performance calculator does the friction calculation for your hose length and diameter, adds it to your lift, and then checks a pump delivers the flow you need at that total head, showing the result green, amber or red. That takes the guesswork out and stops you buying a pump that looks right on paper but underperforms in the pipe.
