Air volume control elimination:

this article explains how to get rid of the AVC or air volume control entirely. AVCs are required to maintain the air charge in a water pressure tank that does not use an internal bladder. By changing the water tank itself we can eliminate this control and its occasional issues.

But there are some things to watch out for, such as leaving old AVC controls in place (a snifter valve in the well?) where they no longer belong.

Getting Rid of the Air Volume Control Valve

Install a water pressure tank that uses an internal bladder

If you convert from a non-bladder type water pressure tank to a water tank using an internal bladder, part of that installation will include the removal of any air volume control valves on the system, including an AVC that may be mounted on the well pump (above-ground jet pumps) or a hidden AVC that is found inside the well piping (submersible well pumps only).

Remove and Discard the Air Volume Control Valve

You can keep the older bladderless water pressure tank and still remove the AVC entirely, abandoning its automatic function, but if you continue to use a bladderless water pressure tank you will need to restore air into the tank from time to time using one of the other methods discussed in this article series:

See WATER TANK AIR, HOW TO ADD

If the the rusty, leaky air volume control valve does not work, can I just remove it?

The short answer is sure. Or if it's not leaking you can leave it in place, which is safer as it avoids disassembly and possible trouble sealing the fittings against water leaks. But if you abandon the air volume control you will occasional have to add air to the water pressure tank when the well pump starts to short cycleor turn on and off too often.

See WATER TANK AIR, HOW TO ADD to fix a short-cycling well pump
or
See SHORT CYCLING WATER PUMP to diagnose other causes of frequent water pump on-off cycling

In 40 years of messing with plumbing I've rarely found an old AVC that worked reliably for long in a residential application. The AVC at left (that round thing in the center of the photo) was found by Langdon who found it to be rusty, leaking, and not working. He replaced it.

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.)

In rare cases an air volume control may put too much air into a pressure tank -

see AIR DISCHARGE at FAUCETS, FIXTURES.

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.

Remove old Air Volume Controls if Changing to an Internal Bladder Water Pressure Tank

Watch out: if you replace a bladderless water tank with a new pressure tank using an internal bladder, you do not want to leave old air volume controls in place.

Those controls will inject air into the water (that is inside the bladder) duplicating the role of the bladderless tank whose air charge is kept separate from the water in the tank.

A result of leaving old AVC components in place might be less water draw-down before the well pump has to run and also air discharge at faucets.

Look for and remove the following, not all of which may be present on your system:

• The AVC or air volume control that was on the water pressure tank - will leave along with the old bladderless water tank if the AVC was attached to the tank itself. But some AVCs are mounted on the well pump and will need to be removed and any connections plugged.
  
  Our photo above shows an AVC mounted right on the well pump - that rusty round disc.
• SNIFTER & DRAIN BACK VALVES - if your bladderless water tank was supplied from a submersible pump in the well there may be a snifter valve on the well piping - a device that injects air into the supply water at each pump on-cycle. This valve should be removed.
• Manual air inlet valves on the well piping above ground, usually close to the old water tank.
  
  Some snifter valve installations included what looks like
  
  a WATER TANK AIR INLET VALVE that can be used to manually add air to the water pressure tank. Normally it'd be just fine to leave such a valve in place, though it's no longer needed. But some of these valves include a soft-spring valve core that is designed to release excess air in the system placed there by the Snifter Valve.
  
  Such valves need to be removed for proper system operation.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2020-07-01 - by (mod) - where do I connect the AVC tube on the water pump?

Mauricio

Thanks for a helpful question,

At the AVC instructions at

AIR VOLUME CONTROLS, REPLACE

we quote a typical installation instruction (Brady) as

... Air Volume Control should be installed into the 1/4” or 3/8” N.P.T. tank port above and closest to the discharge port as shown below.

Goulds Pumps says:

Galvanized tanks are installed the same as pre-charged tanks except they require an Air Volume Control (AVC)to replenish air lost through absorption. The AVC requires connection to a vacuum port on the pump.

The suction side of the AVC must have a minimum 3" vacuum for 15 seconds when the pump starts. Follow the instructions provided with the air volume control.

Check that page and don't hesitate to ask further as needed. You'll see that typically at the pump the AVC is connected to the pump's "suction side" as you put it; on some pumps that port is marked for AVC connections.

On 2020-07-01 by Mauricio

Where in a impeller water pump should I connect the hose to a AVC like the STA-RITE U238-5B, I see there are 2 ports, one near de intake and one closer to the discharge.

I assume one has positive pressure and the other one has a negative pressure.

On 2018-01-26 - by (mod) - where does the AVC connect to the water pump?

James

The AVC connection might be to a fitting on the pump at the impeller chamber or it might connect to a nearby water line at the pump outlet. Designs and hookup specs vary. Tell us the AVC model and brand and we can help find the right instructions.

On 2018-01-26 by James

On the Avc where on the pump does the tubing hook up to.

On 2014-12-30 - by (mod) - Can a air control valve be repaired?

Gerald, AVCs like the one shown at page top are factory-sealed and not field repairable except that a clogged pressure sensor line can of course be replaced.

Other AVCs using a float arm inserted into the pressure tank and/or removable air vents with o-rings can have those parts replaced.

So the answer is "sometimes" depending on the AVC model and type

On 2014-12-27 by Gerald shadrix

Can a air control valve be repaired?

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Continue reading  at WATER TANK LIFE & REPLACEMENT or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• AIR VOLUME CONTROL ADJUSTMENT
• AIR VOLUME CONTROLS, GET RID OF
• AIR VOLUME CONTROLS, HISSING
• AIR VOLUME CONTROL REPAIR repair procedures for Brady and other air volume control devices
• AIR VOLUME CONTROL TEST
• WATER TANK AIR VOLUME CONTROLS - home
• WATER TANK BLADDERS

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AIR VOLUME CONTROLS, GET RID OF at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER SUPPLY, PUMPS TANKS WELLS

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