Understanding Water Pressure
A practical guide to reading the numbers and spotting problems before they cost you.
What does PSI or kPa actually mean?
Standard pressure gauges typically show pressure as PSI (pounds per square inch) or kPa (kilopascals). 1 kPa is the pressure from a 10 cm column of water, so 100 kPa is like having a 10 m tall column of water pressing down. This is a useful mental image for understanding how much pressure your pump needs to push water up to your troughs or header tanks.
To convert: 1 psi ≈ 6.9 kPa. So 30 psi is roughly 207 kPa.PSI is an old measurement but it is still very common as the numbers work well for practical purposes. e.g. 10m of water head is roughly 100 kPa or 14.5 psi.
Reading pump cycles
If your water is delivered by a pressure pump (rather than gravity-fed), you'll see a regular sawtooth pattern in your pressure history. This is called a pump cycle:
- Cut-in pressure: the low point where the pump switches on
- Cut-out pressure: the high point where the pump switches off
- A typical gap between cut-in and cut-out is 50–100 kPa
Example 1 - Healthy pump cycle
Pressure at 200 kPa → pump starts → rises to 280 kPa → pump stops → pressure slowly drops as stock drink → after 40 min, back to 200 kPa → cycle repeats. This is normal.
Example 2 - Short-cycling (possible waterlogged pressure tank)
Pump runs for 30 seconds, stops, runs again after 5 seconds - repeating many times per hour. This indicates the pressure tank bladder may have failed, causing the pump to work much harder than it should.
Example 3 - Hysteresis (pump hunting)
Pressure oscillates between 190 kPa and 210 kPa with very frequent pump starts. The gap between cut-in and cut-out is too narrow - the pressure switch needs adjusting to widen the range to 50+ kPa.
Where to place the sensor
There is no single right answer - the sensor can go at the tank, the pump, or anywhere along the pipeline. Any point on the line gives useful data, so pick wherever is most accessible or practical for your setup.
The best position depends on what you most want to monitor:
- Tank inlet: monitor whether your source (spring, bore, or town supply) is delivering correctly
- Pump outlet: see pump cut-in/cut-out behaviour and detect pump failure quickly
- Scheme connection: if you're on a council or private water scheme, place the sensor at or near your connection point - a sudden drop to zero is an early sign of a burst line or disconnected fitting, before it becomes a large water bill
- Trough header: monitor whether pressure is reaching your stock water points
- Anywhere between: equally valid - a mid-line position still catches pressure drops from leaks, pump failures, or supply issues upstream and downstream
- Pressure drops to near zero and stays there - likely a burst line or failed pump
- Pressure never rises above 80 kPa - pump may be failing or suction side blocked
- Pressure rises continuously without stopping - pressure switch or pump controller may have failed
- Sudden pressure spike followed by a drop - may indicate water hammer from a fast-closing valve