How to Set and Adjust a Water Pump Pressure Switch: Cut-In, Cut-Out and Tank Pre-Charge
- Cut-in starts, cut-out stops
- Big nut = both, small nut = gap
- Tank air 0.2–0.3 bar below cut-in
- Power off before adjusting
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Key Terms
- Cut-in: the pressure at which the pump starts.
- Cut-out: the pressure at which it stops.
- Differential: the gap between them (for example 1.5 bar).
- Pre-charge: the air pressure in the empty pressure tank.
Pressure Switches and Controllers
Pressure SwitchKSh 4,500
PEDROLLO EASY PRESS PUMP CONTROLLERKSh 24,000
H-TECH Instruments and Controllers RangeKSh 1,350| Product | Price |
|---|---|
| Pressure Switch | KSh 4,500 |
| PEDROLLO EASY PRESS PUMP CONTROLLER | KSh 24,000 |
| H-TECH Instruments and Controllers Range | KSh 1,350 |
Current listed prices incl. VAT (updated 13 October 2026).
The H-TECH pressure switch has a regulating range of −0.2 to 7.5 bar and a differential range of 0.7 to 4 bar (see the product page). Electronic controllers combine switching with dry-run protection.
How to Adjust a Pressure Switch Step by Step
- Switch off the power. The terminals inside are live when powered.
- Note the current cut-in and cut-out on the gauge by running the pump once and watching.
- Remove the cover. Find the large spring (range) and the small spring (differential).
- To raise both cut-in and cut-out, turn the large nut clockwise; anticlockwise lowers both. Small turns: half a turn at a time.
- To widen the gap, turn the small nut clockwise (this raises cut-out).
- Refit the cover, restore power, open a tap and watch the gauge: note the start and stop pressures. Repeat until correct.
Set the Tank Pre-Charge
With the pump off and the tank empty of water (open a tap until it stops), check the air valve with a tyre gauge and set it about 0.2–0.3 bar below cut-in. Wrong pre-charge is the commonest cause of rapid on-off cycling. See booster pump and pressure tank guide.
Troubleshooting
| Problem | Likely cause |
|---|---|
| Pump switches on and off quickly | Tank pre-charge lost or a waterlogged tank; small leak |
| Pump never stops | Cut-out set above what the pump can reach; worn pump; big leak |
| Pump will not start | Cut-in too low; blocked switch inlet; no power |
| Contacts burnt or sticking | Switch at the end of its life; replace it |
More pump faults: water pump troubleshooting. Choosing a pump: pump size calculator.
Frequently asked questions
What should my pressure switch be set at?
Many homes use about 1.5–3.0 or 2.0–3.5 bar; stay within the pump’s capability.
Which nut adjusts the cut-out on a pressure switch?
The small nut changes the differential (raising cut-out); the large nut moves both points.
Why does my pump keep cycling on and off?
Usually the pressure tank has lost its air charge or there is a leak.
What should the pressure tank be set at?
About 0.2–0.3 bar below the cut-in pressure, with no water pressure on the tank.
Can I adjust a pressure switch with the power on?
No. Switch off first; the terminals are live.