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This article describes how to adjust the building water pressure by setting the water pump cut-in and cut-out pressure on the pump pressure control switch. We also point to our article on how to adjust building municipal or community water pressure at a building.

We discuss diagnosing and repairing a water pressure control switch that sticks "on" or "off" or simply won't operate, at water pump Pressure Switch Repairs. At WATER TANK AIR, HOW TO ADD we discuss adding the right amount of air to a non-bladder steel or glass-lined well tank. At WATER TANK BLADDER PRESSURE ADJUSTMENT we discuss fine tuning the pump pressure control switch to work perfectly with the exact air pressure pre-charge in a bladder type well tank.

© 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

• How to Adjust Water Pump Pressure: The detailed, step by step procedure for inspecting and adjusting the water pressure control switch is discussed in detail at ADJUST PUMP PRESSURE CONTROL.
• Diagnosing Water Pump Short Cycling on and off: If your water pump is clicking on and off too often or quite rapidly see SHORT CYCLING.
• Diagnosing & Repairing Poor or Lost Water Pressure and Flow: we still have water flowing but pressure and flow quantity are reduced. See WATER PRESSURE LOSS DIAGNOSIS GUIDE
• Diagnosing & Repairing Lost Air in the Water Tank: The problem of lost air in the water pressure tank along with how to correct that condition are discussed beginning at SIGNS OF AIR LOSS. Also see WATER TANK AIR, HOW TO ADD followed by WATER TANK BLADDERS & CAPTIVE AIR and WATER TANK BLADDER PRESSURE ADJUSTMENT
• Diagnosing & Repairing a Water Pressure Control or Water Pump Control Switch: We discuss diagnosing and repairing a water pressure control switch that sticks "on" or "off" or simply won't operate, at water pump Pressure Switch Repairs.
• How to boost water pressure in a building by installing a pressure booster pump and pressure tank is discussed in detail at PUMP, WATER PRESSURE BOOSTER

ADJUST PUMP PRESSURE CONTROL - how to set the water pump pressure

How to Adjust the Water Pump Pressure Control Switch If the length of time that you can run water between pump turning on and off is short, say just a minute or less, the pump is short cycling - or your water pressure tank is a small one that doesn't give a big draw down cycle.

Here we are discussing setting the water pressures at which a water pump will turn on (to get more water) and off (to stop pumping water from the water source into the water tank). Water pumps use a pressure control that specifies the pump cut-in (turn on) and cut-out (turn off) water pressures. Don't confuse the water pressures we discuss here with the air pressures we discuss at WATER TANK AIR, HOW TO ADD.

SAFETY WARNING OF FATAL SHOCK HAZARD: if you remove the cover of the pump pressure control switch you can get access to the two nuts that adjust the operating pressures of the water pump. But watch out! There are also live electrical contacts exposed in this area. If you touch them, especially being near water piping, there is a serious risk of death by electrocution. Watch what you touch, or have a professional plumber or electrician do this job for you. More pump and tank safety warnings are below.

If the water pump apparent "short cycle" is say 1-3 minutes this may be all your system can provide. If however something has changed, and the pump used to run longer, say 2-5 minutes, I suspect loss of air in the pressure tank or an internal problem in the tank (like a hole in the bladder if it's a "captive air" pressure tank). The problem of lost air in the water pressure tank along with how to correct that condition are discussed beginning at SIGNS OF AIR LOSS.

If the "short cycle" is very short, clicking on and off, there could be a different problem with the pump control pressure switch or with a dirty, clogged water filter if one is installed on the system. Dirty water filters as a source of rapid pump on-off cycling are discussed at CAUSES OF SHORT CYCLING.

If you want to set up the cut-out pressure on your pump control, while leaving the "cut-in" down where it is, you'll also get a longer "off" cycle, but if you set the cut-out pressure too high, the pump will just run forever since it can't reach that high pressure. This is easy to figure out since if you set it too high the pump will just keep running. (Then turn it off electrically and set the cutout pressure a bit lower.)

In sum, it might be possible to improve this condition by adjusting the pump control which sets the cut-in water pressure (to start the water pump) and the cut-out water pressure (to stop the pump).

Usually this isn't going to help with pump short cycling but adjusting the water pump can give a longer on-cycle for the pump and it can increase the water system pressure up to a point.

If you ask the pump for more pressure than it can deliver it will simply keep running without ever reaching the cut-out pressure you've specified. If your pump short-cycling behavior has recently gotten worse, don't try to fix it by adjusting the pump pressures, go on to look at other problems like loss of the air charge in the water tank or a defective or clogged pump control or water filter.

Which nut adjusts water pump cut on or cut off?

The nut on the larger spring in the pump pressure switch: Usually the larger nut in the pump pressure control switch adjusts the pump cut-on ("cut-in") AND pump cut-off pressures simultaneously. This is the left-hand spring (and nut) in our photo.

That means that whatever the gap is between the cut-on pressure and the cut-off pressure, that gap is maintained, but the entire operating range of the pump is raised or lowered. Turning the large nut clockwise RAISES BOTH the cut-on and cut-off pressures. So turning the large nut clockwise shifts the whole operating pressure range of the pump UP to HIGHER pressures.

Conversely, turning the large nut counter-clockwise will lower the whole pump operating range. This is the simplest adjustment to make.

Photo (left) courtesy of a reader.

The nut atop the smaller spring in the pump pressure switch: this nut is used to narrow or widen the gap between the pump cut-on and pump cut-off pressures. This is the right-hand spring (and nut) in our photo).

Turning the small nut clockwise (tighter) will RAISE the CUT-OFF pressure, and vice versa, loosening or turning the nut counter-clockwise will lower the cut-off pressure. Watch out! If you loosen this nut too much you can set the cut-off pressure below the cut-on pressure and the pump will turn on and run forever (or until it burns up.)

Which nut to turn in the pump pressure switch control, and which direction to turn it, are usually visible on a label inside the pressure switch cover. Above we show photos of a common Square D water pump pressure control switch and the label with pump control adjustment details. [Click to enlarge].

Here are Example Pump Pressure Switch Adjustment Instructions from Square -D

Understanding how pump pressure control switches work and which way to turn which of the two nuts in the control can be confusing.

On a Square-D Pumptrol® 9013FSF-2 pump pressure switch, for example, Square D tells us that we

• Turn nut #1 (the larger spring) clockwise (to the left) to raise [both] cut-on and cut-off pressures.
  
  In other words, adjusting the pressure on this spring shifts the whole operating range of the switch up or down, but keeps the difference between cut-in and cut-out the same, whatever it happens to be (typically it's about 20 psi from the factory.)
• Turn nut #2 (the smaller spring) clockwise to raise the cut-out pressure only.
  
  In other words, adjusting the pressure on this spring shifts just the pump cut-out pressure up (clockwise) or down (counter-clockwise).

Pump Pressure Control Switch Safety Warnings from the Manufacturer

Square D also has these safety warnings printed on a label attached to new switches. We have expanded the text a bit for clarity:

• Hazardous Voltage: disconnect electrical power before removing the pump control switch cover
• Excessive Pressure: the switch is rated to handle up to 220 psi .

But we add that this kind of pressure could certainly explode some water tanks so be sure not to set the pump to a pressure that is higher than what your water tank or piping are intended to withstand. Absent any other guidance I would not set the water pressure in a building over 70 psi. And I would be sure that a pressure relief valve has been installed on the water tank.

What are the Usual Water Pump and Tank Pressure Control Settings in PSI?

Most residential water systems using a water pressure tank and water pump use one of these two pressure operating ranges:

Low-pressure operating range pumps like low horsepower pumps and many jet pumps

• Cut in (start pumping) - 20 psi
• Cut out (stop pumping) - 40 psi

Higher-pressure water pumps, like submersible pumps, and higher horsepower 2-line jet pumps

• Cut in (start pumping) - 30 psi
• Cut out (stop pumping) - 50 psi

How High Can we Set the Water Pressure in My Building?

You can't just set the pump pressure as high as you want to. Here's what can go wrong with excessive pump pressure control settings:

• Exceeding well pump pressure capability: If you set the cut out (stop pumping) pressure higher than the water pump is capable of reaching, the pump will just keep running indefinitely until it burns up or blows a fuse or trips a circuit breaker or overheats.
• Causing a ruptured water tank internal bladder: we have had a number of reports of ruptured bladders in water tanks. In normal use the bladder in most water tanks is not stressed at all - the internal water tank bladder simply 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.
  
  If your water tank were a less common model in which air were inside the bladder rather than outside it, excessive air pressure could burst the bladder. If you set the water pump pressure too high on one of these systems, you might cause the water bladder to rupture inside the tank. In an extreme case you might blow up the water tank itself. Most water tanks are not designed this way.
• Blowing up a water pressure tank - serious safety hazard: if you set water pressure too high, even if the pump is capable of reaching that pressure it may be unsafe. Most water pressure tanks are designed to operate safely in the water pressure ranges we cited above. If you had the bad luck (and stupidity) as to be using a water tank that has no pressure relief valve installed, it is possible to cause the tank to rupture or even explode, risking damage to the building or even serious injury or fatality if anyone is nearby.
• Causing leaks at fixtures: even if your water tank were rated for high pressure, and even if your water pump is capable of high water pressure, if you run water pressure in a building over 70 or 80 psi you can expect to have recurrent leaks at plumbing fixtures: most water faucets and tub faucets are not designed for high pressure use.
• Also see HOW MUCH AIR TO ADD - How Much Air is needed in the water pressure tank?

WATER PUMP & WATER TANK SAFETY - Water pump and water pressure tank or water storage tank safety advice

While you're on the topic of water pumps, tanks, and controls, here are some safety tips about water pressure tank relief valves and electrical safety around this equipment. Be sure to see our full article on water pump and water tank safety, located at WATER PUMP & TANK SAFETY .

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WATER PUMPS & WELL TANKS
WATER PUMP CONTROLS & SWITCHES
  IDENTIFY WELL PUMP TANK COMPONENTS
  MAIN WATER SHUTOFF VALVE
  WATER PUMP ELECTRICAL SWITCHES
    WATER PUMP PRESSURE CONTROL ADJUSTMENT
    WATER PUMP PRESSURE CONTROL REPAIR
    WATER PUMP PRESSURE CONTROL REPLACE
  WATER PRESSURE REGULATOR ADJUST
  WATER PUMP RELAY SWITCH
  WATER TANK AIR VOLUME CONTROLS
  TANK AIR INLET VALVE
  TANK AIR VALVE REPAIRS
  WATER TANK PRESSURE GAUGE
  WATER TANK DRAIN VALVE
  WATER TANK RELIEF VALVE
  CHECK VALVES
  WATER FILTERS
WATER PUMP TYPES & LIFE EXPECTANCY
WATER PUMP & TANK SAFETY
WATER SUPPLY & DRAIN PIPING
WATER TANK TYPES: WATER, OIL, EXPANSION, ALL
WATER TANK LIFE EXPECTANCY
WATER TANK REPAIRS
  CONTROLS & SWITCHES on WATER TANKS
  INTERMITTENT CYCLING WATER PUMPS
WATER TANK AIR, HOW TO ADD
WATER TANK BLADDERS & CAPTIVE AIR
WATER TANK BLADDER PRESSURE ADJUSTMENT
WATER TANK PRESSURE CALCULATIONS
WATER TANK SIZE & VOLUME
WATER TANKS HOW THEY WORK

• Thank you to Jason Gapco at Education Solutions for careful editing and text suggestions, 12/2008
• Thank you to Steven Prior, a reader, for questions leading to our clarification of the function of the large and small pump pressure control switch springs, and for his photograph of the pump switch springs, 3/23/2009
  
  
• How to Adjust Water Pump Pressure: The detailed, step by step procedure for inspecting and adjusting the water pressure control switch is discussed in detail at ADJUST PUMP PRESSURE CONTROL.
• Diagnosing Water Pump Short Cycling on and off: If your water pump is clicking on and off too often or quite rapidly see SHORT CYCLING.
• Diagnosing & Repairing Lost Air in the Water Tank: The problem of lost air in the water pressure tank along with how to correct that condition are discussed beginning at SIGNS OF AIR LOSS.
• Diagnosing & Repairing a Water Pressure Control or Water Pump Control Switch: We discuss diagnosing and repairing a water pressure control switch that sticks "on" or "off" or simply won't operate, at water pump Pressure Switch Repairs.
• Details on how to Repair the Water Pump Pressure Control Switch are discussed at WATER PUMP PRESSURE CONTROL REPAIR
• Replacing a Bad Water Pressure Control Switch is discussed step by step at WATER PUMP PRESSURE CONTROL REPLACE

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