What is the high pressure cut-off?
The WaterMate Pro pump has a built-in high pressure cut-off switch. This is a safety feature - if the pressure in your system builds up too high, the pump automatically stops to protect itself and your pipework. When the pressure drops again, the pump restarts automatically.
This means you may see the pump cycling on and off during a watering cycle. In many cases, this is completely normal and by design.
How to tell if the high pressure cut-off is triggering
Signs the cut-off is activating:
- The pump starts, runs for a few seconds, then stops, then starts again (stuttering or cycling)
- A low water alarm or pumping fault alarm sounds during watering
- The pump shudders slightly but no water comes out
How to confirm it: Hold the pump body firmly in your hand during a manual watering cycle. If you feel a click or thud as the pump stops, the high pressure cut-off is triggering.
Why does it happen?
High pressure cut-off is most commonly caused by one of the following:
1. Not enough outlets on the zone
This is the most common cause. If a zone has only a small number of drippers, pressure builds up quickly in the pipework because there isn't enough flow to keep the pressure down. Sprayers are less likely to cause this as they release water more freely.
The Pro pump is designed to supply up to 60 drippers per zone. If your zone has significantly fewer than this, consider adding more drippers or outlets - this alone often resolves the cycling completely.
2. A blockage in the pipework
A blocked dripper, kinked hose, or partially blocked filter can restrict flow and cause pressure to build rapidly. Check:
- The inline filter - remove and clean it, or run briefly without it to test
- All hoses for kinks, especially on hot days when hoses soften
- Individual drippers for blockages - remove and soak in warm water if needed
3. Using soaker or seep hose
If you're using soaker or porous hose, the Pro pump will naturally cycle on and off as the hose reaches pressure - this is normal behaviour. In this case, simply turn off the low water alarm for that zone in the Device Control Panel to prevent false alerts.
4. Valves not opening
If a valve is faulty or not receiving a signal, the pump will build pressure immediately with nowhere for the water to go. Hold each valve during a manual watering - you should feel and hear it click just before the pump starts. If a valve doesn't click, see our [valve troubleshooting article].
5. The cut-off switch sensitivity
All Pro pumps leave us factory-set and tested at maximum pressure. In rare cases the cut-off switch may be slightly too sensitive. See the adjustment section below.
Remedies — in order of ease
Step 1 — Turn off the low water alarm
If the pump is cycling but water is still reaching your plants, the system is working as designed. The cycling simply triggers the low water alarm unnecessarily. You can turn this off for the affected zone in the Device Control Panel under zone settings. This doesn't fix the cycling but removes the alarm while you investigate further.
Step 2 — Add more outlets
Adding more drippers or outlets to the zone reduces the system pressure and keeps the pump running smoothly. This is the most effective long-term fix for zones with few drippers.
Step 3 — Add a pressure relief bypass
A practical solution used by many customers is to add a small bypass return pipe - a short length of 4mm pipe connected to the far end of your 13mm distribution pipe, with the other end returning to the water tank. This allows excess pressure to bleed off continuously, keeping the pump running smoothly.
Note: The bypass pipe should be left fully open. Any restriction will cause pressure to build again. A small Hozelock-compatible tap can be fitted but should be left fully open.
Step 4 — Adjust the cut-off switch sensitivity
If the above steps haven't resolved the issue, the cut-off switch sensitivity can be adjusted manually.
⚠️ Please contact us before attempting this adjustment
When to contact us
Get in touch if:
- The pump is stopping immediately on startup with no water reaching your plants at all
- You've checked for blockages and added more outlets but the cycling continues
- You'd like guidance on adjusting the cut-off switch sensitivity
- Joints or connectors are blowing due to excess pressure
Related articles:
- [WaterMate : Pump not running]
- [WaterMate : Troubleshooting]
- [WaterMate : Valve installation]