Colleen Roberts

Complete Guide for a Pressure Switch on a Well Pump System

By Colleen Roberts •  Updated: 12/27/22 •  16 min read
Pressure Tank for a Well with Pressure Switch

4 Reasons to Adjust a Pressure Switch on a Well Pump System

  • To increase water pressure or decrease water pressure.
  • To balance the pump and tank
  • To avoid cavitation
  • To avoid pump damage.

What is a Water Pressure System – Why is it Important?

Before learning how to adjust a pressure switch on a well pump system, it will be helpful to understand the basics of a water pressure system.

Many people do not understand their home water pumping system if they pump water from a well. The following information is a step-by-step guide to help you learn the basics about pressure tanks and what you need to know to adjust a pressure switch on a well pump system.

Where are Pressure Tanks Located?

Pressure tanks, also called bladder tanks, are a vital component of a water-pumping system. Most modern pressure tanks are bright blue, gray, or even white and are often located in a pump house located near the water well, the basement of a home, a designated mechanical room, or even a crawlspace. A water pressure tank is a vessel that stores water under pressure. Manufactured pressure tanks for domestic use are constructed of fiberglass or steel mainly.

How Does a Water Pressure Tank Work?

Your home water pressure tank contains two things: water that enters at the bottom of the tank through the Tank-Tee assembly and compressed air at the top of the pressure tank. A bladder or a diaphragm separates the air and water within the tank.

Under normal conditions, water is incompressible; but the air is mostly gas and is compressible.

Compressed Air is Very Forceful

Air pressure of 40 psi can dislodge chips and other particles and drive them into your face and eyes with shrapnel-like force.

“How to Adjust a Pressure Switch on a Well Pump System”

Once a water pressure tank is full of water, you can place your hand on the tank and will be able to feel where the water is because it will be colder. You can tap the pressure tank with your knuckles to hear the difference. Typically 2/3 water and the top 1/3 will be compressed air.

Important Pressure Tank Safety Warning

If adjusting the precharge air pressure or adding air to a corroded pressure tank, rusted, damaged, or with diminished integrity. The pressure tank can burst or explode, possibly causing severe or fatal personal injury and property damage.

Only adjust the precharge when the pressure tank is new or when the integrity of the tank and lack of internal or external corrosion is confirmed.

Only licensed professionals should check, adjust or recharge the air precharge of pressure tanks. Always wear eye protection when working on a pressure tank.

The maximum allowable inlet water pressure is 125 psi. However, if the daytime water pressure exceeds 80 psi, nighttime pressure may exceed the maximum. Use a pressure-reducing valve to reduce the flow if necessary.

WARNING!
Pressure Switch Danger Warning

Pressure Switch Electricity Hazard Warning

Caution! Electricity can be extremely hazardous, especially when unfamiliar with it. Always use caution working with electricity, and power down the breakers (either a single-pole or a two-pole breaker) in the panel when testing components or preparing to make any adjustments within the electrical system.

Some pumps, typically shallow well jet pumps, require a single pole breaker. Jet pumps can go either way. A single pole breaker typically uses 120-volt circuits, 15-20 amps. They are constructed with one hot wire and one neutral wire.

Other pumps, such as most submersible well pumps, are on single-phase 230-volt circuits and require a double pole breaker primarily used with a 240-volt circuit, 20-60 amps, and consist of two hot wires.

Call a professional if you’re not 100% confident you can do this safely before considering adjusting a pressure switch on a well pump system.

Pressure Switch Electrical Circuit Breaker Instruction Safety Guide

How is Water Pumped to the Pressure Tank

As the submersible well pump pushes water (jet pumps work on suction) from the well into the pressure system, the water enters through the tank tee at the bottom of the pressure tank. As the water volume increases in the pressure tank, the precharged air compresses against the water.

When a water faucet opens in the system, the compressed air in the pressure tanks forces the water out of the pressure tank. As a result, the water system reduces pressure as water is drawn-down.

During draw-down, pressure decreases throughout the plumbing system. As a result, the air precharge becomes less compressed in the bladder tank until the reduced pressure returns to a pre-determined minimum setting of 30 to 40 psi.

Once the system reaches the set point, the contacts on the pressure switch suddenly close, engaging the water pump to refill the pressure tank.

The pressure tank quickly begins to fill, but the load on the pump becomes more challenging as the tank reaches capacity. Because the pump works against the air as it’s compressed, the system is recharging and rebuilding pressure. It’s essential to understand this when learning to adjust a pressure switch on a well pump system.

Once the system again reaches 50-60 psi, the contacts re-open, causing the pump to disengage. This cycle can occur hundreds of times daily in a water system depending on water demand and the pressure tank size, referred to as the water pumping cycle.

By learning how to adjust a pressure switch on a well pump system safely, the pressure settings can be increased or decreased.

Recap – How Does a Pressure Switch Work?

The pressure point that activates the pressure switch is called the set point, and the pressure threshold that deactivates the pressure switch is called the cut-out or trip point.

The pressure switch is electromechanical, a passive device triggered only by two operating points. In the presence or absence of pressure, the pressure switch controls the activation and the deactivation of the water pump when required.

When the water pressure drops below 30-40 psi, the electrical ordinarily open (NO) contacts close, driving the electrical current through the water pump. When the water pressure reaches the 50-60 psi set point, the contacts open to stop the current and deactivate the well pump, ceasing the water pumping cycle.

How to Adjust a Pressure Switch on a Well Pump

Unscrew the small nut and tug up to remove the cap from the pressure switch

To remove the cap from the pressure switch, remove the nut as shown in the diagram and give the cover a quick tug upward to release it from the pressure switch.

Identify the Pressure Switch Default Settings

As the cut-out pressure on the pressure switch can be increased if your water pressure is low, consider increasing the pressure. Although Increasing the pressure is possible, there are risks involved!

You need to check your pressure switch, tank, and pump’s safety rating to ensure you do not exceed the maximum pressure the components can bear. Increasing the pressure will undoubtedly increase your energy cost, as the pump works against higher head pressure.

Still, more importantly, if a pressure switch adjustment is incorrect, it can destroy your water well pumping system.

In the worst case, adjusting a pressure switch can cause harm or injury as the pressure tank could explode. Therefore, be extra cautious when increasing the cut-out pressure on your water well pumping system.

Many home water systems do not have a safety valve installed, also known as a pressure relief valve. However, a safety valve should always be installed even if the pressure system is correctly calibrated. Therefore, it would be better to remain with the factory default settings when it comes to cut-out settings.

Before adjusting the pressure switch on a well pump system, it is essential to identify the preset on the pressure switch and what kind of adjustments it provides.

30/50 psi vs 40/60 psi preset pressure switch settings

Understand Your Pressure System Equipment

Please note that the manufacturers’ default pressure range (set-point pressure to cut-out pressure) is indicated on the packaging or labeled inside the pressure switch cover as shown above.

Understand the capacity of the water pump. If you increase the demand for the pump to build more pressure than its ability to deliver, the well pump will keep running without ever reaching the specified cut-out pressure. If you have a deep well pump unable to build to 60 PSI, you may have no idea the submersible a spinning itself to death at the bottom of the well.

I’ve not mentioned it in this article, but there’s a 20/40 PSI low-pressure switch available, but in 30 years, I have seldom seen one in use. I do primarily work on deep well systems and some shallow ones.

I suggest replacing a pressure switch rather than over-adjust one may be better. For example, if you are going to try to increase a 20/40 PSI switch to 40/60 PSI it will require 8-9 full turns on the nut, and that may be excessive.

As you can see in the image below 8-9 full turns on the pressure range adjustment nut might over-tighten the pressure spring, maybe even to the point that the pressure switch will not work as intended. Just a point to note.

Auto/Off Lever for a Low-Pressure Cut-out Pressure Switch

If you have a low-pressure cut-out switch, you will notice a small brass lever attached to the left side of the pressure switch. The lever is used to open or close the contact points manually.

A low-pressure shut-off switch shuts the pump down if the water pressure in the waterlines drops below the cut-in pressure (low number).

If there was a leak or break in a water line, it might cause the pressure in the waterline to decrease and cause your pump to engage and pump water indefinitely.

This could cause flooding in your home or other building and significant damage. The low-pressure shut-off switch would cause the contacts to open and disengage the pump if the pressure drops 10 PSI below the cut-in pressure.

Some water wells tend to go dry; this, too, will cause a low-pressure situation. While a low-pressure cut-out switch is functional and may provide some protection, I would install a pump protection monitor instead. More costly but has additional benefits and less of a headache in some situations. But, some protection is undoubtedly better than no protection when it comes to pressurized water systems!

To engage a well pump with the lever on a low-pressure cut-out switch the contacts need to be manually held together until the pressure gauge reaches at least 30 PSI. If the pump has not built enough pressure, the contacts will remain open and the pump will stop. Hold the lever up tight, then gently let go of the lever once the pressure is at 30 PSI. Be careful not to touch anything else.

Pressure Switch – Terminals

The terminals on a pressure switch are the points where the incoming and outgoing power leads are connected to the switch providing power.

Pressure Switch – Contacts

The pressure switch contact points are made from a conductive material of 90% silver and 10% nickel to complete the electrical circuit allowing power to the pump motor. When the contacts points on a pressure switch are opened, the electrical circuit is broken and the water pump will deactivate

Pressure Switch – Diaphragm

The diaphragm on a pressure switch is made of flexible material that pushes against the block as pressure increases in the bladder tank. When the preset cut-out pressure is reached, the diaphragm forces the contacts to open, deactivating the power to the water pump.

Pressure Switch – Adjustment Springs

The adjustment spring(s) aims to increase or decrease the cut-in and cut-out pressure settings. Some pressure switches have a smaller secondary spring to adjust the differential setting, which is used only to raise or decrease the cut-out setting. For the most part, it is recommended that the differential is not adjusted.

Do Not Exceed Well Pump Pressure Capability

Never set the pressure switch too high; plenty can go wrong. If the pressure switch cut-out ( pump stops) is set higher than a water pump can reach, it will keep running until it either trips a circuit breaker or overheats and even burns out the pump motor eventually.

WARNING!

Possibly Rupturing the Pressure Tank’s Bladder

In everyday use, the bladder in a pressure tank is not overworked or stressed at all – the internal bladder moves up and down as water enters or leaves the tank – pressure on either side of the bladder (air on one side, water on the other side) remains the same.

Pressure tanks with air inside the bladder are not standard; with this tank style, excessive air pressure could burst the bladder.

Can a Pressure Tank on a Well Pump System Explode?

Thankfully most water pressure systems are installed with a pressure valve. The relief valve protects water well tank systems from pressure buildup. However, I have rarely heard of a pressure tank bursting; I believe one explosion resulted in the death of a plumber due to blood loss.

Pressure Tank Corrosion or Rust

Corrosion would be another issue, and if a pressure tank on a well pump system has visible rust or corrosion on the outside of the tank, there’s a good chance of a more significant problem with the structural integrity of the pressure tank’s interior. 

Before increasing pressure on a corroded tank, complete a new pressure tank installation before adjusting the pressure switch on a well pump system.

Well Pump Systems and Water Lines 

We have discussed that a malfunctioning pressure switch can cause the water pump to run too often or too long and potentially burn out the motor.

In addition, if the pressure switch allows the pressure to go too high, it can put excess stress on the tank and pipes, potentially causing them to crack or even burst.

Over-adjusting a pressure switch on a well pump system can cause the device to malfunction. 

Routine plumbing and water well system inspection are essential to ensure proper operation of the water well system and plumbing to prolong its operational expectancy and monitor the quality of the water it supplies with regular water testing.

Where is the pressure switch located on your well pump system?

WARNING:

Remember, if you are still not 100% sure that you can do this, then please call an expert; it’s just not worth the injury or the cost of possibly damaging your water pumping system. If you are at all apprehensive, then please STOP right here!

Click Here for a Local Expert

Here is a Step-by-Step Guide for Adjusting the Pressure Switch on a Well Pump System.

Air Pressure Settings for Well Pump Pressure Tank

Bladder style pressure tank air pressure adjustment is as follows. A small compressor works excellently for this task, and a bicycle pump will work too.

Set the air pressure in the empty water tank to 2 psi below the well pump pressure switch cut-in pressure. Test with a tire pencil gauge.

  • Cut in 20 PSI – 18 LBS air precharge.
  • Cut in 30 PSI – 28 LBS air precharge.
  • Cut in 40 PSI – 38 LBS air precharge.

Bleed air pressure out of the water tank, or add air pressure into the bladder tank, until the tank pressure is properly precharged.

For example, if your well pump pressure switch is set to “cut in” (start pumping water from the well) at 30 psi, then set the pressure tank to (30 – 2) = 28 psi.

You will need to drain the pressure tank if you adjust the air precharge in the pressure tank.

Safety Diagram to Adjust a Presssure Switch

Initial Steps to Adjust a Pressure Switch on a Well Pump System 

  1. Turn off the breaker(s) to your well pump
  2. Remove the cover from the pressure switch.
  3. Range Adjustment Steps

For the range adjustment on a pressure switch, follow the instructions carefully. 

  1. Find the pressure range adjustment nut on your pressure switch (tall screw).
  2. Turn the range adjustment screw clockwise to increase the cut-in (set-point) and cut-out pressure. Turning the nut no more than 3 turns to start (with a 3/8th wrench) will tighten the pressure adjustment spring. 
  3. Replace the pressure switch cap, turn the power back on to the pump, and test the new pressure setting before making further adjustments. Everything needs to be done in small increments when adjusting a pressure switch on well pump system and testing the results often until it’s set safely and correctly.  

How to Decrease Pressure on a Well Pump Systems

  1. Counterclockwise will decrease both pressures accordingly.
  2. As discussed earlier in the article, it will change both the cut-in and cut-out pressures simultaneously at the same time.

Steps to Adjust Pressure Switch Differential

Follow the following steps for differential adjustment only if you need to change the factory preset of usually 20 LBS:

  1. Find the pressure differential nut on your pressure switch (short screw).
  2. To increase the cut-in pressure, turn the differential screw clockwise. To decrease the cut-in pressure, move the screw counterclockwise.
  3. Cut-in & Cut-out adjustment Steps
  4. Find both the cut-in as well as cut-out screws on your pressure switch.
  5. Move the cut-in screw clockwise to increase the cut-in pressure. Moving it counterclockwise will decrease it.
  6. To increase the cut-out pressure, move the cut-out screw clockwise. Similarly, moving it counterclockwise will decrease the cut-out level.

Final Steps to Adjust a Pressure Switch

  1. Start the water pump to verify your new settings.
  2. Let your water pump run to verify the new cut-out pressure until it reaches the new cut-out pressure. You can check the current pressure on the pressure gauge attached to the tank tee. If the pump stops at the desired water pressure, you have successfully reset your new cut-out pressure.
  3. To verify the cut-in pressure of the water pumping system, drain your open water faucet while watching the pressure gauge until it reaches the newly adjusted cut-in pressure that you have set. The well pump motor will start on the new cut-in pressure if it is appropriately set.

Caution:

If you set the cut-out pressure or the left adjustment spring too high and the well pump keeps running without stopping and opening the contacts on the pressure switch, the safety valve may fire, the breakers may kick out or you’ll overheat or burn out the pump. It is also possible that the tank might explode. Shut down the well pump immediately if the pressure rises to a dangerous level. 

Also, be very careful with increasing the cut-out pressure.

YOUR LOCAL EXPERTS

What’s More Important Than Having Water in Your Home? Having None!

Keep you water system running is tip-top condition! Avoid costly repairs and waking up to no water when you are least prepared… inspecting and serving your water well system is a wise investment!

Water systems need to be services and should only be worked on by a qualified well pump and water system expert.

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