Photograph of a water pressure tank air volume controlAir Volume Control (AVC) Hissing Noise
Cause & response to air hissing at the water tank air volume control

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Air hissing sounds at the water tank: this article explains the causes of a hissing sound of air escaping at the air volume control at a water pressure tank - a condition that may be normal and may not require repair.

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Hissing Sound Coming From the Air Volume Control?

Hissing air volume control valve (C) Daniel FriedmanWhat Causes an Air Hissing Sound Versus Water Leaks at AVCs

If you may hear air hissing in at this air volume control fixture (it's working). Hissing air at the air volume control means that the control is releasing excess air from inside of a bladderless water pressure tank.

But if you see water leaking out of the air volume control, that means it needs repair or more likely, replacement..

Here is a perspective view of where air volume controls are typically installed on a steel water tank. You won't see a control like this installed on a bladder-type captive air water tank.

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. When it does not, and when hissing is followed by water leaks we recommend replacing this air volume control.

Watch out: we do not recommend trying to disassemble this valve. And its response pressure is factory set. If you mess with the brass lock nut and vent you are changing the operating pressure range of the air volume control valve.


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