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PLUMBING TOPICS
WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER PRESSURE REGULATOR ADJUST
WATER PRESSURE REPAIR GUIDE & COSTS
  Questions about lost water pressure
  Advice to a homeowner
  Adjusting Water Pump Pressure Control
  Right Repair to Pump & Tank?
  Well Pump & Tank Replacement Costs
  Reliability of Pump & Tank Repairs
  WATER PUMP PRIMING PROCEDURE
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
WATER PUMPS & WELL TANKS
WATER PUMP & TANK SAFETY
WATER PUMP & TANK CONTROLS & SWITCHES
  WELL PUMP PRESSURE CONTROL ADJUSTMENT
  WATER PRESSURE GAUGE ACCURACY
WATER PUMP TYPES & LIFE EXPECTANCY
  WATER PUMP, ONE LINE JET
  PUMP, TWO LINE JET
  PUMP, SUBMERSIBLE
  PUMP, WATER PRESSURE BOOSTER
  PUMP & TANK REPAIRS & COSTS
  PUMP & TANK SAFETY
WATER PUMP SHORT CYCLING
  SHORT CYCLING PUMP CAUSES
WATER PUMP & WATER TANK REPAIRS
WATER PRESSURE REPAIR GUIDE & COSTS
WATER PRESSURE LOSS DIAGNOSIS GUIDE
WATER PUMP PRESSURE CONTROL ADJUSTMENT
WATER PUMP PRESSURE CONTROL REPAIR
WATER PUMP PRIMING PROCEDURE
WATER PUMP WONT STOP RUNNING
WATER SUPPLY & DRAIN PIPING
  CLOGGED DRAIN DIAGNOSIS
  CLOGGED SUPPLY PIPING / Tankless Coil & Hot Water
  PIPING IN BUILDINGS
  SEWER GAS ODORS
  WATER PRESSURE LOSS DIAGNOSIS
WATER TANK TYPES: WATER, OIL, EXPANSION, ALL
  CAPTIVE AIR BLADDER WATER TANKS
  STEEL WATER TANKS
  BIG WATER STORAGE TANKS
  OPEN WATER TANKS
WATER TANK AIR, HOW TO ADD
  WATER TANK AIR VOLUME CONTROLS
  WATER TANK AIR ADD AT AIR VALVE
  WATER TANK AIR ADD BY DRAINING
  WATER TANK AIR HOW MUCH TO ADD
  WATER TANK AIR HOW OFTEN TO ADD
  WATER TANK BLADDERS & CAPTIVE AIR
  WATER TANK BLADDER PRESSURE ADJUSTMENT
WATER TANK LIFE EXPECTANCY
WATER TANK PRESSURE CALCULATIONS
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 LOSS SIGNS
WATER TANK REPLACEMENT
WATER TANK SIZE & VOLUME
WATER TANKS HOW THEY WORK
WATER SOFTENERS
WATER TESTS, CONTAMINANTS, TREATMENT
WELLS CISTERNS & SPRINGS
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  WELL LIFE EXPECTANCY
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  WELL SHOCKING GUIDE
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Waterlogged water pressure tank schematic (C) Carson Dunlop How to Add Air to a Water Pressure Tank - Air Volume Control
InspectAPedia®  -    

  • How to restore lost air in a building water pressure tank
  • Water tank air volume controls, what they are, how they work - AVCs
  • Well pump & water tank diagnosis & repair procedures
Our site offers impartial, unbiased advice without conflicts of interest. We will block advertisements which we discover or readers inform us are associated with bad business practices, false-advertising, or junk science. Our contact info is at InspectAPedia.com/appointment.htm.
Photograph of a water pressure tank air volume control

This article describes how to add air to a building water pressure tank and it reviews the function and repair of water tank air volume controls in a building water supply system where a private well is the water source. Air volume controls are found normally only on older type bladderless steel water tanks (photo at left) and not on bladder type captive air water tanks. Therefore the procedures describe here are intended for conventional non-bladder type water pressure tanks such as the water tank shown in our photo (left). If your well tank is a "captive air" or bladder type pressure tank such as the Well-X-Trol™ series see WATER TANK BLADDER PRESSURE ADJUSTMENT.

Bladder type or captive-air water pressure tanks and their repairs are described at WATER TANK TYPES and at WATER TANKS HOW THEY WORK.

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 illustration at page top is courtesy of Carson Dunlop, Inc. in Toronto. The round air volume control photographs shown here and just below are courtesy of Ben Langston.

WATER PUMP CONTROLS & SWITCHES contains advice on how to adjust water pressure and water pump cut-in and cut-out pressures.

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

How to Add Air to a Water Pressure Tank

There are fancier methods than those described below but here are three simple methods, of which the second two work well for easy replacement of air lost from a water storage or pressure tank.

1: AIR VOLUME CONTROLS - Method 1: air-volume controls on water tanks

Photograph of a water pressure tank air volume control

An "automatic" air volume control (AVC) device may be installed on the water pressure tank if it's an older, bladderless steel tank. The AVC is intended to automatically put a little bit of replacement air into the tank from time to time as water pressure cycles up and down, that is, each time that the water pump runs.

If you see a round steel disc of about 4" diameter and about 1" thick on the water tank, mounted perhaps at the middle of the tank height or at the water outlet to the tank, or perhaps on the side of the tank with a plastic or copper tube connecting the disc to a fitting on the tank or nearby piping, this is the AVC.

If the air volume control valve is working properly, it uses the pressure changes caused by the cycling on and off of the water pump to automatically add air to the water tank when it's needed. Makeup air is needed in these water tanks because over time the air charge in the tank is absorbed into the tank's water.

The most common versions of air volume controls look like a disk of about three inches in diameter, as we show in the photographs here. A copper or plastic tube that extends from the AVC to a fitting on the water pump itself, as we showed on the photograph above. Look at the fitting screwed into the side of the water tank about 2/3 of the way up from the tank bottom and on the right side of the water tank in the photograph above.

In that picture as well as in this close up of an AVC you can also see the small diameter copper tube which connects the air volume control valve to a fitting (usually) on the water pump itself so that the valve can respond to the cycling on and off of the water pump (and changes in water pressure).

Photograph of a water pressure tank air volume control

 

A second common version of air volume control valve is shaped like a small rectangular steel box with fittings similar to the round model. In this photograph you can see the small object connected to the side of the water tank near the top right side of the tank in this photograph.

There is no copper tube connected to this AVC. Here is a close-up photograph of this more rectangular type of air volume control.

Bladder type water tanks do not use an air volume control valve: Air volume control valves are present only on steel water tanks which do not include an internal bladder to keep water and air separated inside the water tank. In other words, if your water tank is one of the newer models which uses an internal bladder, you won't find an AVC installed.

A bladder-type water tank keeps the air charge separated from the water. The air is in the tank and the water is inside the bladder inside the tank. Thus the air charge does not become lost by absorption into the water.

Does the air volume control valve work? Can it be removed? In 40 years of messing with plumbing I've never found one of these that works reliably for long. An air volume control on a water pressure tank can be left in place but don't count on it to work. If the air volume control valve itself is leaking or fittings on its tubing leak, you may decide, as do many plumbers, to simply remove it.

Just screw in a pipe plug where it was mounted on the water tank, and a smaller (usually brass) plug may be needed at the point of connection of the other end of the copper tube if one was installed on your system.

(You'll have to turn off the pump and release water pressure and drain some water from the tank before replacing an AVC with a new one or with a pipe plug.)

If your AVC is not working or has been removed, and if your water tank is a non-bladder type system, you'll need to use one of the other methods discussed here for adding air to your water tank when it's needed. Forget this method for maintaining the proper air charge in a water tank, except for the Leaky Air Volume Control tip below.

Leaky Air Volume Control Tip: sometimes when you've taken water pressure off of the tank and are refilling it by air using one of the other methods below, you may hear a hissing coming from the tank. Air may be leaking out of an opening at the base of the air volume control. It's valve parts may be partly "stuck" from having moved so seldom or having got clogged by debris.

Usually if this is happening you can simply push your finger over the hole where you feel air escaping.

Some air loss is common at this point, but it should stop on its own. If it doesn't, tap your finger on the hole a couple of times and the air hissing will probably stop. If not you may need to call a plumber to replace this annoying part. Sometimes we tap the control (gently) with a wrench to see if this will stop the leaking. It has always worked for me - so far.

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PLUMBING TOPICS
WATER PRESSURE & FLOW MEASUREMENT
WATER PRESSURE LOSS DIAGNOSIS GUIDE
WATER PRESSURE REGULATOR ADJUST
WATER PRESSURE REPAIR GUIDE & COSTS
  WATER PUMP PRESSURE CONTROL ADJUSTMENT
  WATER PUMP PRESSURE CONTROL REPAIR
  WATER PRESSURE REGULATOR ADJUST
WATER PUMPS & WELL TANKS
WATER PUMP CONTROLS & SWITCHES
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 PUMP SHORT CYCLING
  SHORT CYCLING DETECTION
  SHORT CYCLING CAUSES
  WATER TANK AIR LOSS SIGNS
WATER TANK AIR, HOW TO ADD
  WATER TANK AIR VOLUME CONTROLS
  WATER TANK AIR ADD AT AIR VALVE
  WATER TANK AIR ADD BY DRAINING
  WATER TANK AIR HOW MUCH TO ADD
  WATER TANK AIR HOW OFTEN TO ADD
WATER TANK BLADDERS & CAPTIVE AIR
WATER TANK REPLACEMENT
WATER TANK BLADDER PRESSURE ADJUSTMENT
WATER TANK PRESSURE CALCULATIONS
WATER TANK SIZE & VOLUME
WATER TANKS HOW THEY WORK
WATER TESTING
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL, PUMP, TANK LIFE EXPECTANCY

  • Ben Langston, generously contributed the photographs of round disk-type air volume controls used at the top of this article.
  • Alan Carson, Carson Dunlop, Associates, Toronto, has permitted our use of the well and water pump system used at the top of this and some other pages at our website.

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