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This article describes how to determine the proper air pressure setting in a bladder-type well tank, when, and how to actually change the air pressure in the water tank. Readers of this document should also see Water pump and pressure tank repair diagnosis & cost an specific case which offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost. The page top photo shows the author testing the air pressure in a Well-X-Trol 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 Select the Proper Air Pressure Charge for a Bladder-Type Well Tank

According to Well-X-Trol, bladder type well tank air precharge: typical factory set air pressure on a bladder-type residential well water tank is 18 psi. Some models may come with different pressure settings however. WELL-X-TROL™ water pressure tanks are shipped from the factory with a standard precharge of

• 18 psig for models WX-101 and WX-102
• 38 psig for models WX-103 - WX-203
• 38 psig for models WX-205 through WX-350.

Before discussing doing anything to a bladder-type water pressure tank, read this safety warning from WELL-X-TROL, a leading well tank manufacturer:

DANGER! EXPLOSION HAZARD.
WHEN THE WELL-X-TROL HAS BEEN IN SERVICE AND A CHANGE TO A HIGHER PRE-CHARGE
PRESSURE IS NECESSARY DUE TO A REQUIRED CHANGE IN THE PRESSURE SWITCH SETTING, FAILURE TO
FOLLOW INSTRUCTIONS BELOW CAN CAUSE A RUPTURE OR EXPLOSION, POSSIBLY CAUSING SERIOUS OR FATAL PERSONAL INJURY, AND/OR PROPERTY DAMAGE.

• DO NOT ADJUST OR ADD PRESSURE IF THERE HAS BEEN A LOSS OF AIR.
  
• DO NOT ADJUST THE PRE-CHARGE PRESSURE IF THERE IS VISIBLE EXTERIOR CORROSION.
• DO NOT ADJUST THE PRE-CHARGE PRESSURE IF THERE HAS BEEN A REDUCTION OF THE PUMP
  CYCLE TIME OR THE PRE-CHARGE PRESSURE COMPARED TO ITS INITIAL SETTING. THIS IS BECAUSE REDUCTION IN PUMP CYCLE TIME CAN RESULT FROM LOSS OF TANK AIR PRESSURE WHICH IN TURN CAN MEAN THERE MAY BE INTERNAL CORROSION AND ANY REPRESSURIZATION OR ADDITIONAL PRESSURE COULD RESULT IN RUPTURE OR EXPLOSION.

How to Read Water Tank Pressure or any Pressure Gauge Accurately

If you are fine-tuning water tank bladder or air pressure be sure that you are using an accurate pressure gauge and that you know how to obtain an accurate pressure reading. See WATER PRESSURE GAUGE ACCURACY for details.

Well Tank Air Pressure at Time of Tank Installation

Set the well tank air pressure to 2 psi below the well pump control switch cut-in pressure. We detail this procedure just below. Remember to use your separate air pressure (tire) gauge to check the actual water tank pressure when your well pump turns on and off - that's because the dial gauge installed on your water tank may be inaccurate.

Well Tank Air Pressure Adjustment during Water System Maintenance or Repair

If you need to tune your bladder-type water tank to work exactly properly with your pump pressure control switch, or if you know that someone has already modified the pressure in your water tank and you want to restore it to factory specifications, a reasonable procedure is the following recommended by the manufacturer:

• Remove all water from the water tank. This means turn off the water pump, open a nearby plumbing fixture, run water until the water stops entirely - your water tank should be empty or close to empty.

• Check the air pressure in the water tank by using an accurate air pressure gauge (such as a dial type or digital tire pressure gauge) to measure the air pressure at the schrader valve on the water tank. The tank pressure should be within 10% of the original factory water tank pressure setting. Our photo (above left) shows the water tank air inlet valve on the top of our Well-X-Trol well tank. We removed the cap and label for the photo.
  
  Our photo at above right shows our digital air pressure gauge measuring the air pressure in the water tank. The reading of 39 psi tells us that the dial pressure gauge that we illustrated at How to Read Water Tank Air Pressure Accurately (and located on this same water system) agrees with our pressure gauge within 1/2 psi.
  
  Because water tank pressure controls normally use a pressure difference of 20 psi between the cut-in pressure and cut-off pressure at the water tank, a gauge error of one or two psi is not a concern. Thanks to Jeff Garmel for suggesting text clarification in this discussion of water pressure tank diagnosis.
• Set the air pressure in the empty water tank to 2 psi below the well pump pressure switch cut-in pressure. Bleed air pressure out of the water tank, or add air pressure into the water tank, until the tank pressure. For example, if your well pump pressure control 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.
  
• Replace the air cap on the tank air pressure valve and be sure that any warning labels that you took off during cap removal are back in place.

How to Fine Tune the Pump Pressure Control Switch to the Water Tank

Well-X-Trol offers excellent advice which we paraphrase below:

Because well pump pressure control switches are not precise, "lab grade" instruments, the actual pressures at which a pump control switch turn the pump on or off will sometimes be above or below the stated pressure setting on the package of the control switch or above or below the pressure range shown on the switch itself (if your switch has such markings, most do not).

A difference between the marked pressure settings on a control switch and its actual performance can cause a
delay between the time that a water pressure tank becomes completely empty and the time that the pump turns on. Usually this delay is brief, though some readers have reported that their pump simply did not turn on at all under these conditions.

We want to adjust the water pump pressure switch to be"tuned to the Well-X-Trol (or other brand) bladder-type water tank air pressure that was set at the factory (or is presently the actual pressure in the tank). Here is the procedure:

1. Close off all plumbing fixtures that are using water in the building.
2. Turn on the water pump and let the system run until the water pump cuts off.
3. Open one or more plumbing fixtures to drain the water pressure tank; during this draining, watch and listen to the water tank and pump.
4. If there is a momentary pause in the water flow from the time the well water pressure tank is emptied and the time that the water pump starts, adjust pump cut-in setting clockwise slightly to increase the pump cut-in (turn on) setting. If your water pump is in your well rather than on or next to your water tank, you can't hear the pump run. But you can listen for the "click" of the pump switch cutting in or out. For more photos and description of exactly which nut or screw to turn to adjust the well pump switch cut-in, see WATER PUMP PRESSURE CONTROL ADJUSTMENT.
5. Close the plumbing fixtures and let the water pump continue to fill the water tank until the water pump cuts off.
6. Check time it took to fill the water tank.
7. Open the same plumbing fixtures again, follow the steps above, this time to see if pause in water delivery has been is eliminated. If not, continue adjusting pressure switch.

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Use links just below or 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.

WATER TANK TYPES: WATER, OIL, EXPANSION, ALL
  CAPTIVE AIR BLADDER WATER TANKS
  STEEL WATER TANKS
  BIG WATER STORAGE TANKS
  OPEN WATER TANKS
WATER TANK LIFE EXPECTANCY
WATER TANK REPAIRS
  CONTROLS & SWITCHES on WATER TANKS
  INTERMITTENT CYCLING WATER PUMPS
  WATER PUMP SHORT CYCLING
  SHORT CYCLING DETECTION
  SHORT CYCLING CAUSES
WATER TANK AIR, HOW TO ADD
  WATER TANK AIR LOSS SIGNS
  WATER TANK AIR VOLUME CONTROLS
  WATER TANK AIR ADD AT AIR VALVE
  WATER TANK AIR IN BY DRAINING
  AIR HOW MUCH TO ADD
  AIR HOW OFTEN TO ADD
WATER TANK BLADDERS & CAPTIVE AIR
WATER TANK CAPTIVE AIR vs TRADITIONAL WellMate
WATER TANK BLADDER RESSURE ADJUSTMENT
WATER TANK PRESSURE CALCULATIONS
WATER TANK SIZE & VOLUME
WATER TANKS HOW THEY WORK

• Thanks to Jeremy Houser who suggested that we needed to clarify the difference between bladder type and non-bladder type water tanks when discussing air charging and diagnosis of water tank repairs.
• Thanks to Jeff Garmel for discussing clarifications on water pressure tank testing and diagnosis, 8/24/2009.
• Amtrol Extrol™ pressure control tanks, which they call well tanks, are described at the company's website at www.amtrol.com/extrol.htm and installation and operating instructions for these well tanks can be found at www.amtrol.com/pdf/9015A290revcWXT.pdf
• Well-X-Trol: Amtrol Extrol™ pressure control tanks used on hydronic heating and other systems such as models 35LBC, 50 LBC, 85 LBC, and 100LBC to 600 LBC also use a bottom bladder containing air - see amtrol.com/pdf/LBCSeriesEXTROL9017-095.pdf for details.
• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• Wessels Company bladder replacement store was found at westank.com/bladder-tank-store.php on 5/22/2009. Wes sell refers to "shock and surge tanks" as ASME replaceable bladder type and pre-charged hydropneumatic tanks used for commercial, industrial, and well water systems.

If You Need Help Diagnosing a Loss in Water Pressure or Other Pump & Well Problems See These Guides

WATER PRESSURE LOSS DIAGNOSIS GUIDE
WATER PRESSURE & FLOW MEASUREMENT
  Water Pressure Intermittent
  No Water Pressure
  Well Tank relation to Water Pressure
  Shaking the Water Tank?
  Water Pressure Tank Problems
  Water Pressure Tank Diagnosis
  Water pressure Later Returns "on its own"
  Water pipe clog diagnosis
  Water pipe clog repair guide
  Making the "right" repair
  Typical Water Tank & Pump Prices

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