Air discharge at a tub spout (C) Daniel FriedmanDiagnose & Repair Air Discharge at Faucets
or at Water Supply Piping / Fixtures

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How to diagnose & fix air coming out of faucets:

This article describes the causes of air discharging from building water supply piping or plumbing fixtures or the sources of excess air in water pressure tanks, water supply piping, or other plumbing fixtures.

If air blasts out of your faucets or fixtures we explain what's going on, why it's a problem, and how to diagnose and fix the trouble.

Some air discharge or bubbling issues in building piping are not serious, while others could spell expensive trouble. We list the various causes of air discharge at faucets or shower heads and how to correct each one.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Causes of Air Discharge from Building Plumbing Fixtures

Bladder type water tank (C) Daniel FriedmanAir blasts or air bubbles coming from plumbing fixtures such as faucets, showers, or toilets may be a temporary problem that cures itself or it may be a sign of a deteriorating water well.

Here we list various causes of air in building water supply piping and fixtures to help in diagnosing and repairing this problem. We are going to cover the following:

Excess air in the water pressure tank or well piping system: causes and cures.

Significance of large bursts of air at faucets & Significance of fine white bubbles in water taken from a faucet.

Signs of loss of well water & Signs of well piping leaks. Signs of water pump failure.

Water pressure tank air volume control problems: How to restore lost air in a building water pressure tank.

What is a snifter valve used on a well water system and how do they work? Hidden and antique air volume control valves and features can explain well pump rapid cycling problems & air discharge troubles at faucets & fixtures.

[Click to enlarge any image]

Question: Why is air coming out of my faucets, what does it mean, and what can I do to diagnose and fix the problem?

For a couple months now we've had excessive air in our water lines, similar to after there has been a power outage and the water spurts out of the faucets. I'm trying to figure out a solution to our water issues.

We continuously have air in our water supply at all faucets, toilets, and showers; the air is intermittent, and spurts out while water is running, anywhere from immediately after faucet is turned on to a couple minutes later (in shower, for instance).

Flushing the toilet results in the pipes or toilet valve banging. we have a well that's 204' deep, and the submersible pump was replaced in July 2005 (five years ago).

Our water pressure tank is working fine, turning on/shutting off at 30/60.

After shutting off, with no water running, the pressure holds steady at 60. When the pressure tank is drawing water from the well, you can hear and feel the pipe from the well drawing in a lot of air from the well the cold water has the air problem much more than the hot water for whatever reason (please advise!), on two of our faucets with separate hot/cold handles, the cold water won't come out anymore.

Did the spurting of the air/water lodge mineral deposits in the valve or something to prevent cold water from coming out, but allowing hot water to flow?

the flow rate out of our faucets varies from normal at times to very low pressure we don't have a water treatment system we don't have a venturi valve that I know of (we bought the house 5 years ago) or that I can find

I don't know the static level or the recovery rate of the well, and with our air/water problem, I'm not confident that I'd get a good reading.

A licensed plumber came out yesterday (very kind, offered a free estimate) and looked at the pressure gauge on the pressure switch (between the incoming supply line from the well and the pressure tank) and concluded that it's something to do w our well or well pump.

He suggested that either the well may be running dry or that the screen may be clogged up. He suggested I get some friends and pull up the well pump and examine it. - T. C., Purcellville, VA


From your description it sounds as if your well water level is dropping and the pump is sending a mix of water and air into the building piping. If that turns out to be the case, it might be possible to increase the well yield - a step less costly than drilling a deeper or new well.

But first take a look through the causes of air in building water piping that we describe just below. If the problem were simply a leak in the water piping between well and house, for example, that would be less costly to repair.

List of common causes of air in water, or air coming out of plumbing faucets and fixtures:

Consider that because under normal conditions building water supply piping and fixtures are pressurized with water, a leak or opening in a pipe or fixture would be expected to leak water out, not air in to the plumbing system. But there are some exceptions that we describe below.

Air blasts, or air sputtering out of plumbing faucets means there is air in the water supply system. Below we diagnose the most likely causes and thus the cures for this problem.

Article Series Contents

Why Air Overcharge in the Water Pressure Tank Can Cause Air Discharge at Plumbing Fixtures

Photograph of a water pressure tank air volume control

If in placing an air charge into a bladderless steel or fiberglass water pressure tank the tank is overcharged air may flow out of the tank, through piping and out of plumbing fixtures when water is turned on.

This condition only occurs if the tank is one that does not separate water from air using an in-tank bladder. In this case the problem is self-correcting, typically in just a few minutes of running water at each fixture, as excess air flows out of the tank, through piping, and out at fixtures.

As the water pump cycles back on and water is pushed back into the water tank, operations will resume normally.

For details see WATER TANK AIR, HOW TO ADD


Air Discharge from Hot Water Faucets

Watch out: if you find air discharging only from your hot water faucets a dangerous condition may be present: the hot water heating system may be too hot, risking scalding or even water heater explosion. Turn off power or fuel to the water heater itself and call a licensed plumber immediately.

Air particularly wants to convert from dissolved gas to bubble form at water heaters, so often a plumber will install devices such as a microbubble resorber or an air vent right at the water heater to address this problem.

Microbubble resorbers and other air eliminators at the water heater are discussed at AIR ELIMINATORS for POTABLE WATER SUPPLIES.

How a Burst Water Pressure Tank Bladder Can Cause Air Discharge at Plumbing Fixtures

Bladder type water tank (C) Daniel Friedman

If a "captive air" bladder-type water pressure tank has a ruptured bladder, depending on the total air charge or pressure, air may be forced out of the pressure tank and through piping and fixtures as above. As with our first example, the air flow will be temporary.

But in this case the water pressure tank will become waterlogged and the water pump is likely to be short-cycling before long


A new water pressure tank or a bladder replacement will be needed. We discuss captive-air water tank bladders, their maintenance, bursting, and repair,


How a Bad Check Valve can Cause Air Discharge at Plumbing Fixtures

A defective or improperly installed check valve on a private pump and well system can also cause air discharge from the building's faucets. A faulty check valve that allows water to drain back into the well causes negative pressure or "suction" that can draw air and contaminants into the well piping or into the well itself.


Air burst or air leaks into water from a bad check valve at a sillcock (C) Daniel Friedman

Watch out: when diagnosing the cause of air discharge from building faucets, it's easy to misdiagnose the cause: from inside the building the symptoms of a bad check valve (loss of prime, possibly air discharge at plumbing fixtures) can look a lot like a hole in the well piping, especially if the hole is in the pipe rising inside the well itself (also causing loss of prime, air at faucets) - as we discuss further just below.

A leaky sill cock check valve or backflow preventer (shown above) might also introduce air into building water pipes.

How Leaks in the Well Piping Can Cause Air Discharge at Plumbing Fixtures

Schematic of a shallow well single line jet pump water system (C) Carson Dunlop AssociatesExperts note that when the pump shuts off, if there is a hole or leak in the well piping, the hole allows air into the well line; when the pump is running, water sprays out of the same hole, possibly adding to rust and debris in the well and the pumping of silty or dirty water into the building.

While water piping is under pressure and water leaks out rather than air leaking in, if we have the combination of lost water pressure (for example during an electrical power loss or a well system being shut down), and leaks in the well piping, as water drains backwards into the well air may be drawn into the water piping through piping leaks.

If the piping leak is inside the well casing where plenty of air is available, and if the well piping includes a defective (leaky) foot valve or check valve in the well, this cycle could repeat and building occupants may see recurrent air discharge from plumbing fixtures.


You may be able to diagnose this problem by turning off all water supply in the building and watching what happens to the water pressure gauge at the pressure tank.

If the water pressure falls slowly even when you are sure no water is running in the building, there is probably either a bad foot valve or check valve in the well, or a leak in the water piping between the well and the building. But watch out - water pressure gauges can be inaccurate or slow to respond to changes in water pressure -


Air Leaks in well piping, connections, check valves, fittings, or even the pump itself: leaks anywhere between the well and the building can introduce air into the well piping and water supply system.

Air can leak into well piping anywhere between the top of water column in the well at the end of a pump cycle (that's somewhere below the top of the static head of the water column), and the water pressure tank: that includes both vertical and horizontal sections of well piping.

Mineral deposits show air and water leaks at a pump installed in this Minnesota home (C) Daniel Friedman

Leaks in well piping or at valves or check valves, at the pitless adapter o-rings, or even at the pump itself (shown above). A pinhole leak can be hard to track down, especially on the suction side of pumping systems where you won't see water leaks. Low water in a well that allows a pump to draw air also places a lot of air into the water supply system.

If there is a severe well piping leak or a water piping leak or running plumbing fixture in a building the well pump may begin to run continuously


Watch out: a hole or leak in a well pipe or a defective or improperly installed check valves on a private pump and well system can also cause air discharge from the building's faucets.

A faulty check valve that allows water to drain back into the well causes negative pressure or "suction" that can draw air and contaminants into the well piping or into the well itself. See details


Experts note that when the pump shuts off, if there is a hole or leak in the well piping, the hole allows air into the well line; when the pump is running, water sprays out of the same hole, possibly adding to rust and debris in the well and the pumping of silty or dirty water into the building.

See WATER SUPPLY / DRAIN PIPE LEAK TYPES for details on diagnosing types of water piping leaks.

Also see PUMP PRIME, REPEATED LOSS of for additional diagnostic help with well piping and foot valve leaks.

How Loss of Water in the Well Can Cause Air Discharge at Plumbing Fixtures

A falling water table or decline in well recovery rate may cause the well pump to send a mixture of water and air into the well piping and building.

If this condition is occurring you might notice that the air discharge at plumbing fixtures is intermittent: when no water has been run overnight and the well has recovered, once existing in-piping air has blown out, the water flow may appear normal, without air discharge.

But as well water level drops and the well is slow in recovering, the air discharge problem will return. In sum, these well or well and pump conditions can cause air to be delivered by the well pump into the building's water supply piping:

If your well yield (how much water you can get out of the well) is inadequate water level in the well may drop low enough for air to enter a submersible (in well) pump or into the foot valve.

The combination of a too-small STATIC HEAD, WELL DEFINITION (water reserve) in the well and a poor flow rate make this problem more likely. A well that has performed adequately in the past may no longer have an adequate yield for a variety of reasons: drought, a drop in the water table, drilling of new wells nearby, or yield loss due to mineral clogging of rock fissures that feed water to the well.

If the well pump is too large incapacity (pumping rate) for the well's safe yield then air may be drawn into the well pump and water piping when the pump drops water level in the well too low.

The safe yield for a well may change if the water table drops. Then, if the well pump output rate exceeds the safe yield for the well, air may be injected into the building water piping and the well pump may be damaged.

See inadequate WELL FLOW RATE for more information.

See WELL YIELD DEFINITION where we define safe well yield.

See WATER PRESSURE STOPS, RETURNS - for symptoms of loss of water in the well and slow well recovery rates.

See WATER PRESSURE LOSS DIAGNOSIS & REPAIR for our complete article series on diagnosing loss of water or water pressure at a building.

Defective or Damaged Well Pump Can Cause Air Discharge at Plumbing Fixtures

It is possible that a failing well pump may introduce air into the water supply piping system due to cavitation (a vacuum forming inside the well pump mechanism), causing dissolved gases to come out of solution.

Cavitation and air leaks into a water pump may be more likely with an above-ground jet pump and less likely with a submersible in-well pump that would be expected to be always submerged in water.


If a new well pump has been installed and is over-sized, the level of water in the well may be drawn down too rapidly when the pump is running, resulting in air entering the pump and being delivered to the building. This condition can also occur in times of drought or if your well is running dry.

Defective Air Volume Control Can Cause Air Discharge at Plumbing Fixtures

An air volume control device may be installed on some bladderless water tanks to attempt to keep the proper air charge in the water tank. If the air volume control is leaky or not working properly it may be overcharging the water tank with air.

If this is the case the air discharge from plumbing fixtures will be chronic.


Gases in the Well and Water Supply Can Cause Air Discharge at Plumbing Fixtures

In some areas gases, including potentially dangerous explosive methane gas, may leak into the water supply and may be delivered into the building water piping from a well. Other gases often found in well water include radon, CO2 in some locations, and dissolved sulphur (that rotten egg smell).

Watch out: methane gas in well water is a pollutant and may be explosive. According to experts such as the New Hampshire Department of Environmental Services,

Methane at high concentration is explosive and thus there is a fire hazard if large amount of water with methane are used near an open flame in a closed space.

The presence of methane gas in water can be simplistically detected by agitating a small volume of water in a plastic container in an outdoor location and attempting to ignite the gas released. Have a neighbor present when you try this testing.

If you have such a well you should contact your local department of environmental services and your building department.

Lowering the settings of the pump’s start/stop switch and/or providing an air release vent on the water storage tank at the high point of the stored water might allow this “off gassing” to occur at a point other than your faucet. Since this is a natural condition, and no damage is caused, there is no need to take any particular action.

Dissolved gases may also be present in water but would not normally appear as bubbles or air blasts at a faucet. These include radon, carbon dioxide, hydrogen sulfide (rotten egg smell), or other gases from dissolved organic matter or chemicals.

But in some deep wells water at the well bottom, at higher pressure, may hold dissolved gases that convert to bubble form when water pressure is reduced to ambient air pressure at building faucets.

Changes in water temperature also affect the amount of gases that remain dissolved in water - warming water drives gases out of solution.


Test to Identify Methane Gas in the Water Supply

Other common gases found in water besides methane include CO2 and sulphur or dissolved sulphur.

Keech and Gaber describe how to collect a test sample for methane and also describe options for removing gases from water.

Bad Snifter Valve or Drain-Back Valve Can Cause Air Discharge at Faucets

Snifter valve on a submersible pump well system © D Friedman at

Snifter valves and drain-back systems used on submersible pump and well systems that use a bladderless water pressure tank (or whose bladderless water tank was replaced with an internal bladder water pressure tank) can push excess air into the water pressure tank.

Snifter valves & drain-back valves along with air volume control devices (AVCs) form a three-part air volume control system designed to

This system is used on deep wells and lake water supply systems for which the pressure tank does not use an internal bladder. The required air charge in the pressure tank is kept at the proper level by drawing some air into the well piping system at the end of each pump-on cycle.

The pump stops, water drains back down the well pipe into the well, air is drawn into the system at an above-ground air admittance valve, often by what looks like a tire valve or Schrader valve located on well piping close to the pressure tank.

In the photo I'm pointing to the air admittance valve part of a snifter valve sysem on a bladderless water pressure tank in a home in Two Harbors Minnesota.

The snifter valve (or any other air volume control device on a water pressure tank) can fail in either of two modes:

For more information start reading at SNIFTER & DRAIN BACK VALVES and also see details at DRAIN BACK & SNIFTER VALVE SYSTEM COMPONENTS

Watch out: If a bladderless water tank that used a snifter valve system is replaced with a new internal-bladder tank you may need to have a plumber pull the well piping to remove the (now no longer used) drain and vent found inside the well.

In the well an air-introducing check valve is installed above the top of the static head of the water column to add air to the bladderless water tank at each pump cycle.

Even if the bladderless water pressure tank was replaced with a new bladderless tank, if the snifter valve system was left in place but the excess air vent was not installed on the new tank (or is not working) you'll want to provide or repair these components.

Water Softener Check Valve Can Cause Air Discharge at Plumbing Fixtures

Water softener Brine Tank Pick Up Tube Air Check Valve - Fleck at InspectApedia.comQuestion: why do we get air at our faucets after the water softener has gone through a regeneration cycle

2017/02/21 Quiggley said:

I have a Kenmore 625.393060 water softener and have the same problem of there being air in the water lines after a regeneration.

Typically, my first use of water after a regeneration is with a toilet flush in the morning. There is always a noticeable release of air in the water line as the toilet tank refills. What caused this?

Image: a replacement water softener brine tube air check valve produced by Fleck and widely sold at plumbing suppliers as a repair or replacement check valve for many water softener brine tanks.

This question was posted originally at WATER SOFTENER CLEANING & SANITIZING

Reply: look for a clogged check valve on the brine pick-up tube or a leak in the brine tube between softener and brine tank

Two common causes of air discharge at plumbing fixtures that is traced to the water softener are

  1. a pinhole leak in the brine tube between the softener and the brine tank
  2. a clogged air check valve on the bottom of the brine pick-up tube in the brine tank

A leak in the brine tank tubing can be the problem. As brine is returned to the softener during a regen cycle it may be accompanied by air that later shows up at building plumbing fixtures.

You should also pull out, inspect, and clean the brine pick-up tube in the brine tank. An air check valve located (usually) on the bottom of the brine pick-up tub is intended to prevent air from being drawn into the water softener from the brine tank.

At the end of the regen cycle the level of salty water in the brine tank falls low enough that a ball type check valve on the bottom of the brine pick-up tube drops to prevent air from being drawn out of the brine tank and into the softener.

Pull out the brine pickup tube and place the air check valve on its end into a jar of vinegar for a few hours or longer to dissolve mineral deposits including salt that may be causing it to jam. Some suppliers suggest using bleach - that makes little sense to me. Rinse the valve in fresh water and restore it into the brine tank.

If you have any doubt about the valve or if you can't convince yourself it's operating freely, just replace it. A widely-sold air check valve for brine tanks is the Fleck J-Tube 3/8 " X 34 " Long. This check valve can be trimmed, if needed, to fit your salt tank.

See WATER SOFTENER BRINE TANK AIR CHECK VALVE for details about this part.

At our FAQs for water softeners at DIAGNOSE WATER SOFTENER PROBLEMS we also discuss air in the water system after a water softener regen cycle.

A less obvious cause of air discharge at fixtures may correlat with resin loss from the water softener - that's a problem in the softener itself, discussed in detail at WATER SOFTENER RESIN LOSS - symptoms of resin loss from a water softener and how the problem may be repaired

Water Treatment Equipment Can Cause Air Discharge at Plumbing Fixtures

Water treatment equipment can also inject air into a building water supply. Water treatment to remove odors or gases from the water supply may use venturi air injectors intended to remove iron, manganese, or odors. Properly installed these devices should not send air out of faucets. But the following conditions can cause air injector treatments to place excess air in the building water supply piping:

Other Sources of Air in Water Piping - Work on Municipal Water Mains or Private Well Piping

Site excavation (C) Daniel FriedmanWe list the most-common sources of air in water supply systems starting at AIR DISCHARGE at FAUCETS, FIXTURES

There may be other causes of air discharge from building water supply piping, including the ones we list below.




Air Eliminators for Potable Water Supply Systems

This topic has moved to a separate article. Please see AIR ELIMINATORS for POTABLE WATER SUPPLIES

2016/06/08 Mike P said:

We have very deep bedrock well - 385 ft deep. It produces 16 GPM. From the beginning the water has been full of small bubbles. I am almost certain the bubbles are not mechanically produced as they occur when water is drawn directly from the well manifold before reaching any of the faucets and filtration systems.

There are so many bubbles when water is drawn from the manifold it is milky white, not just cloudy. It takes well over a minute for a 20 OZ glass of water to clear.


Continue reading at AIR ELIMINATORS for POTABLE WATER SUPPLIES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see AIR DISCHARGE at FIXTURES FAQs - questions & answers about air sputtering at faucets or other plumbing fixtures and at their continuation at AIR DISCHARGE at FIXTURES FAQs-2






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