The Well Pump Pressure Switch: What It Does
The pressure switch turns the pump on and off at set pressures. Here is how cut-in and cut-out work and why adjusting it is professional work.
Quick Answer
The pressure switch is the small electrical box that turns your well pump on when pressure drops to the cut-in setting and off when it reaches the cut-out setting. Common factory settings are 30/50 or 40/60 psi (cut-in / cut-out). Because the switch carries line voltage, inspecting contacts, replacing it, or adjusting it is electrical work for a qualified professional.
How the switch works
The switch senses system pressure. When you use water and pressure falls to the cut-in value, the switch closes and powers the pump. When pressure climbs to the cut-out value, the switch opens and stops the pump. The pressure tank stores water between these points so the pump is not cycling every time you open a tap.
Common settings
| Setting (psi) | Cut-in | Cut-out | Suggested tank pre-charge |
|---|---|---|---|
| 30/50 | 30 | 50 | About 28 psi (≈2 psi below cut-in) |
| 40/60 | 40 | 60 | About 38 psi (≈2 psi below cut-in) |
The pressure tank’s pre-charge is typically set to about 2 psi below the cut-in pressure. If the switch setting is changed, the tank pre-charge usually needs to change to match. This is one reason the two parts are adjusted together, by someone who understands the system.
Signs of a switch problem
- The pump will not start even though pressure is low.
- The pump will not shut off at the normal cut-out pressure.
- Rapid clicking or chattering at the switch.
- Burnt or pitted contacts (something only a pro should open the cover to inspect).
Do not adjust an energized switch
Frequently asked questions
- What is the difference between 30/50 and 40/60?
- They are just different cut-in/cut-out pairs. 40/60 keeps household pressure higher and is common in newer systems; 30/50 is an older default. Either should be matched to the pump, tank pre-charge, and plumbing.
- Why does tank pre-charge have to match the switch?
- Pre-charge is set about 2 psi below cut-in so the tank delivers usable water before the pump restarts. A mismatch causes short cycling or poor pressure, so changing one usually means re-checking the other.
Sources & references
- Protect Your Home’s Water: Private Wells — US EPA, accessed October 29, 2026
This guide is documentary research and general information, not a laboratory analysis or professional assessment of your specific well. See our disclaimer.