How to Test a Water Well Pressure Switch

Water well pressure switches control the well pump for operation. The switch is typically directly connected to the pressure tank on the water system. A small ¼ inch diameter pipe nipple makes this plumbing connection. Plumbed separately into the water system is a pressure gauge. The pressure gauge is a necessity for accurately testing the pressure switch. Observing the operation of the pressure switch in concert with the pressure gauge readings will allow you to test the switch for proper operation.

Things You'll Need

• Voltmeter
• Plumbers pliers
• Pressure gauge (optional)
• Teflon tape (optional)

Instructions

Voltage Test

1. Remove the cover on the pressure switch. Use the voltmeter to check the voltage coming into the switch and the power going to the well pump. Place the voltmeter in the "volts" position. Insert the red lead into the connector marked "volts". Place the black lead into the connector identified as "com" or common.

2. Identify the power feed wires. There are two sets of contacts on the pressure switch that are electrically tied to the screws below, an inside set and an outside set. A pair of wires will be terminated to one each set of screws on the pressure switch. One pair is the power feed and the other pair of wires will be going to the pump motor.

3. Touch the red lead on the meter to one of the screws connected to the power feed wires. Touch the black lead from the meter to the other wire of the matching pair. The meter should read 220VAC. Remove the meter leads.

4. Open a faucet to drain water from the system. The pressure switch contacts should now be touching and the pump running. Touch the meter's leads to the other set of contacts where the wires are running out to the water pump. The meter should read 220 VAC. If the meter fails to read the same voltage as the power feed, the switch maybe bad. Proceed to the next section to test the switch for proper adjustment.

Switch Operation

1. Check the operation of the pressure gauge during the pumps operation. Generally the factory settings are left installed on the pressure switch. This will show itself in the readings on the gauge. Read the range in pressure on the gauge. Typically the pump should come on at 30 PSI (pounds per square inch) and shut off at 45 PSI. Flick the gauge with your fingers if it fails to register any reading.

2. Replace the gauge if it fails to register. Remove all electrical power from the pump system. Drain the water system. Remove the old pressure gauge with the plumbers pliers. Wrap a few rounds of Teflon tape around the threads. Install the new gauge. Tighten it with the plumbers pliers.

3. Reapply power to the water system. Observe the small contacts on the switch. The small copper discs should be touching or in the closed position.

4. Observe the gauge as the pump is running. The pressure gauge needle should be rising. As the gauge approaches the 45-PSI reading, the switch should open the contacts. If the switch did open and shut the pump off, the switch is good.

5. Adjust the switch if the gauge reading was higher than 45 PSI. There are two nuts on the pressure switch. Turn the smaller nut one turn in a counter clockwise direction. This will lower the shut off pressure. Open a water valve and observe the pressure gauge. Turn the larger nut on the pressure switch one turn in a clockwise direction to raise both the pump on and pump off pressure. Perform this action only if the pump on pressure becomes lower than 30 PSI.

Tips & Warnings

• Follow all local electrical codes whenever installing new devices.

• Water and electricity do not mix. Ensure that the electrical power is off whenever touching exposed electrical connections.

References

• Test a Pressure Switch
• Adjust the Pressure Switch

Resources

• National Ground Water Association