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What Is a Well Pressure Switch and How Does It Work?

Posted by John Woodard on November 30, 2023

well water systemA well pressure switch is the heartbeat of a well water system. When it does not work properly, smooth water flow cannot be achieved, and other components within the system will not operate at peak efficiency. Knowing what duties a well pressure switch performs can help you monitor the health of your water, notice issues with your devices, and have a better understanding of how to elongate the life of your well water system. Below you can find information on what a well pressure switch is, how it works, symptoms of failing pressure switches, and how to diagnose and resolve these complications.

What is a well pressure switch?

A well pressure switch is a device that turns a well pump on or off based on water pressure inside a well water system. Unlike high pressure switches and low pressure switches used in HVAC applications, each well pressure switch possesses a cut-on and cut-off pressure that determines when the switch turns the pump on and off. A well pressure switch ensures that a well pressure tank does not get too full or too empty. Without a pressure switch, a pump would need to run every time a faucet or other fixture is opened in a home. Well pumps are not engineered to operate rapidly or continually, so this constant on and off would shorten the life of the pump drastically.

Learn more: What is a well pump and how does it work?

How does a well pressure switch work?

A well pressure switch works by turning a well pump on when the system’s pressure decreases to the cut-on point and switching it off when the pressure increases to the cut-off point. Common thresholds for pressure in a well system are 40 and 60 psi, 30 and 50 psi, and 20 and 40 psi. When the pump is turned off and water is flowing to a home, the air inside the pressure tank expands, and the pressure decreases. Once the pressure reaches the cut-on point, the well pump turns on and begins filling the tank. As water enters the tank, the air inside compresses, causing the pressure to increase. Once the pressure reaches the cut-off point, the switch turns the pump off until enough water is used in the home to activate the switch again. This cycle optimizes the workload of the pump by allowing it to turn on only when the tank is near empty and turning off when the tank is nearly full.

Well pressure switches utilize springs to set the pressure for the cut-on and cut-off points and electrical wiring to send on/off signals to the pump. Mechanical switches contain a diaphragm that presses against a piston and spring inside the device. When the pressure on the diaphragm is great enough, the diaphragm remains pressed against them. Once the pressure reaches the cut-on point, the diaphragm eases up on the piston and spring, activating the switch.

Types of well pressure switches

There are two types of well pressure switches: mechanical and electrical. The main difference between these two types of switches is how the pressure applied to the inside of the switch is utilized to operate the switch.

Mechanical pressure switches require physical contact to create a signal, while electrical pressure switches do not need direct contact to read pressure. Electrical pressure switches must have continuous access to power, while mechanical switches send an electrical switching signal without needing an electrical supply. Electrical switches feature configurable cut-on and cut-off points via buttons on the switch itself, but mechanical switches contain factory-set points that can be changed with a pressure-adjusting nut. While both types of pressure switches can be used for a well, mechanical switches are less expensive and therefore much more common.

Common well pressure switch problems

When a pressure switch stops working properly, you will notice it inside your home. However, symptoms of a bad well pressure switch often mean there is a fault elsewhere in your well water system. You can avoid many problems with your system by having it inspected annually. Diagnosing problems before they cause a noticeable difference in the water within your home can save you money, time, and the headache brought on by replacements and repairs.

Faulty well pressure switch symptoms

Common symptoms of a failing well pressure switch include the following:

  • Water pressure inside the home above the pressure switch’s cut-off point
  • Low water pressure inside the home
  • Pump turns on and off repeatedly
  • Pump does not turn on at all
  • Pressure tank is waterlogged
  • No water flow at all inside the home

All of these symptoms may be signs that your pressure switch is failing, but they may also signal a problem elsewhere in your system. For example, a pump may fail to turn on because the pressure switch fails to send a signal, or the mechanics of the pump itself may be broken. Because of this, having a professional inspect your equipment is essential in diagnosing the problems within your system. Below you can find causes and solutions to common well system symptoms.

How to test a pressure switch on a well

When a symptom of a bad pressure switch becomes evident, check that the power to the well has not been turned off before trying anything else. The well switch will be located near the pressure tank. If the switch was already on, check the breaker to ensure it did not trip. A breaker that trips regularly is a sign of a faulty well pump. Once you know that power is running to your well system, you can test the pressure switch.

To test a well pressure switch, follow these steps:

  1. Turn the power off to your well system. Testing your well’s system with the power turned on can lead to electrocution.
  2. Remove the switch’s cover. This may require a few screws to be undone.
  3. Check if water is leaking out of the switch. If so, tighten it and observe if the leaking stops.
  4. Check the switch’s contacts. If any of the contacts are damaged, the switch needs to be replaced. If not, clean the contacts until you can see the shine of the metal.
  5. Ensure that the wires inside the switch are secure.
  6. Check that the pressure adjustment nut is tightened to the correct pressure.

Once these steps are complete, restore power to your system and test if the pump turns on and off at the appropriate intervals.

well pressure gauge

Common well pressure switch problem solutions

Some well pressure switch problems require full switch replacement, while others may simply necessitate a piece of the switch to be replaced. Other well system problems may seem like they are caused by the pressure switch but are the result of other components and not the switch itself.

No water flow from pump

If there is no water flowing from your pump and, as a result, no water flowing in your home, the pressure switch may be to blame. The most likely pressure switch issues in this instance are worn-down contacts or a loose spring. These prevent the switch from activating the pump when the pressure reaches the cut-on point. If the electrical contacts are worn down, the entire switch must be replaced. A loose spring, on the other hand, can be switched out without needing the entire unit replaced.

If you have ruled out any problems with your switch and there is still no water flow, other devices may be the culprit.

  • Low water table. During a drought, the water table in your well may be too low for your system to access.
  • Power loss. A common cause of well system issues is a lack of power caused by a power outage or power surge. Ensure that the circuit is turned on.
  • Clogged filter. Sediment can infiltrate the water system and lead your filtration systems to become clogged. You can temporarily bypass your filters to ensure that this is the issue. Do not use the bypassed water for any purpose as it can be full of contaminants.

Pressure switch won’t turn on or off

If your pressure switch will not turn on or off, it can cause massive issues inside your home and well system. If a pump does not turn off, the pressure tank will fill too full and create water pressure that is too high. Once the tank fills all the way and becomes waterlogged, the water pressure inside your home will drop drastically. A pressure switch failing to turn on and off can be an issue with your pump or pressure switch springs. If the pump does not operate at the appropriate pressure, the cut-on or cut-off points may not be reached. Likewise, if your switch cannot accurately detect the pressure, it may not activate or deactivate the pump. If you test your pressure switch and notice the springs are worn down, you can simply replace them.

If you have inspected your switch and everything seems in order, hire a professional to check for issues with your well pump. Well pumps contain many more complicated parts than pressure switches, so attempting to check the pump without experience can be challenging and lead to accidental pump damage or a misdiagnosis of the problem.

Learn more: How to Check Your Well Tank’s Pressure

Pump cycles repeatedly

The rapid turning on and off of a pump is known as short cycling. While this may seem like a problem with the pressure switch, it is most likely caused by the well pressure tank. If the bladder of a pressure tank ruptures, the pressure inside of it is no longer regulated. The pressure switch relies on the pressure inside the tank to be regulated, so under certain conditions it can repeatedly switch on and off. A pressure tank with a ruptured bladder must be replaced immediately. If replacement is delayed and the system runs, the pump and pressure switch can both be damaged quickly.

Learn more about wells: How to fix common well pressure tank problems | How to size your well tank | Well contamination symptoms




If you have any further questions, please do not hesitate to contact our water experts.

Comments 1-10 of 2

My water is unreliable due to having to keep filing the points on both this my new pressure switch, and also my old one, which was replaced for this reason. I just nearly burned up the elements in my 80 gallon water heater. Is there a reliable mechanical switch, or would an electrical pressure switch would be a better way to go?

John on May 01, 2023

Low water pressure.

Rose Marie Fayne on March 27, 2023
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