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💧 Understanding Pressure Switches and Manometers in Pump Systems

Whether you're setting up a new water pump or troubleshooting an existing one, understanding how pressure switches and manometers work can help ensure a stable and efficient system.

Let’s break down the basics using the popular PM12 pressure switch and a standard pressure gauge (manometer), like the ones shown in the image below.


🔌 What Is a Pressure Switch?

A pressure switch is a mechanical or electronic device that turns your pump ON or OFF based on the pressure in the system.

In a typical water pump setup:

  • When pressure drops below a certain point (e.g., water usage), the switch turns the pump ON.

  • When pressure rises back to the set maximum (e.g., tank fills), the switch turns the pump OFF.

This automatic cycle protects the system and saves energy.



Pressure switch open
Pressure switch open

đŸ› ïž How to Adjust a Pressure Switch (PM12)

Inside a PM12 mechanical pressure switch, there are two key adjustment screws:

  1. Range Nut (Main Spring):Controls the cut-in pressure (when the pump starts).🔄 Turn clockwise to increase, counterclockwise to decrease.

  2. Differential Nut (Side Screw):Controls the cut-out pressure (when the pump stops) by setting the gap between start and stop.🔄 Turn clockwise to increase the stop pressure.


  • ✅ Example Factory Setting:

    1. Start at 3 bar (≈30 meters of water head)

    2. Stop at 5 bar (≈50 meters)

If your system has varying demands (like different buildings or long pipe runs), each switch may need individual adjustment.




🧭 What Is a Manometer (Pressure Gauge)?

A manometer, or pressure gauge, helps you monitor the real-time pressure in the system. It’s an essential tool during setup and maintenance.

In the photo shown, the gauge measures in bar and PSI.

  • 1 bar ≈ 10 meters of water head

  • If your gauge reads 4.5 bar, the water pressure is about 45 meters

Always use a manometer when adjusting the switch to avoid guesswork.

Manometer
Manometer

⚠ Common Problems and Solutions

Problem

Cause

Solution

Pump turns on/off too frequently

Pressure gap too narrow

Increase differential (nut #1)

Pump doesn't stop even with closed valve

Cut-out too high or pressure too low

Lower cut-out or check pipe losses

Switch not responding

Worn switch or wiring issue

Check or replace the switch

📎 Final Tips

  • Adjust in ÂŒ or Âœ turns, then test.

  • Always loosen the differential nut first, then set the range, and re-tighten.

  • Monitor pressure live using the manometer during setup.

For more technical guidance, see the full PM12 pressure switch manual or reach out to your installer.

Need help setting up your pump? Contact us or schedule a support visit. We're here to help ensure your system runs reliably for years to come.

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