How to Fix Air in Hot Water Lines

Aug 31, 2021 | Home Improvement Repair, Plumbing, Skills Specialties

When your faucets or toilets spew and sputter when you turn them on before they start putting out water, you may have air in your water lines.

When the air gets trapped in the water pipes, it can cause issues with how the water flows out of the faucet. Instead of a consistent, steady stream, you may have varying water pressures, or the water may spew out in sputters. Air in hot water line can also cause pipes that hiss, clank, or vibrate when you have them on at low pressure.

The type of water supply system you have can play a role in causing your water lines to get air trapped inside. Keep reading to learn about the signs, causes, and how to fix air in hot water lines. 

What Causes Air In Hot Water Lines?

Knowing what type of water system you have will help you when it comes to identifying the cause of air in your water lines. For example, if the air issue is in both the cold and hot water lines, it will need a different treatment than if it’s solely in the hot water supply. 

Well-fed water systems are at higher risk of air in the water lines. There are three potential issues – the check valve, methane gas, or a shallow feed line. 

Line Shut Off For Maintenance

Water systems that are gravity-fed or supplied by a municipal organization typically get air in the water lines after the water has been turned off to perform maintenance. Usually, once you turn the water on and let it run for a while, all of the air will push out. However, if you’ve had a new water heater put in or you’ve had recent plumbing work that required your water to be turned off, it can cause air to get trapped in the pipes. You can also have this issue if your water is cut off at the supplier level.

Pro tip: If your water looks discolored once it comes on after being off, it’s normal. Most water contains sediments (hard water) that will settle when the water isn’t running. The flowing of the water is pushing these particles free of the pipes. As long as the issue doesn’t persist past a few minutes, there’s no problem.

Faulty Check Valve

One of the most severe causes of air in a hot water line is a faulty check valve. Check valves are found on well systems and private pumps located near the pump. When the check valve goes faulty, water can drain into the wall, creating negative pressure – suction. This suction can pull contaminants and air into the piping or the well. In addition, if the valve is loose, it can cause air to fill the water lines. Tightening the valve can repair the issue.

Pro tip: You may want to call in a professional to examine check valves. When a check valve gets damaged, it can allow dangerous contaminants into your water lines. Making repairs or replacements is crucial if this is the issue causing your water line to have air.

Methane Gas

On occasion, the air in the water lines can be due to methane gas. This gas is flammable, but it’s typically harmless to your water supply since it dissolves in water. Methane is a natural type of gas that is sometimes present in well-fed systems. 

When the temperature inside the well rises but the pressure drops, it can cause methane to enter the water. You can remove methane from your water using aeration. Once you detect methane levels in your system, you’ll want to do regular checks to ensure this problem does not continue to occur.

Well Feed Line Too Short

If you have a well for the source of your water supply rather than water that comes from a city system, there could be an issue with installing your well that causes air to get trapped in the water lines.

For example, if the feed line that goes down into the well is too short to go down deep enough to draw up the water correctly, the process can cause air to enter the water lines. To repair this problem, you can add a few extra feet of hose to go deep enough into the water that it doesn’t capture air. 


Well-water systems have particular challenges in climates that experience droughts. If more water comes out of your system than is going in from rainfall or other groundwater sources, it could lead to the water levels dropping below your pump intake point. When the water gets too low, the pump will suck in air as it’s struggling to pull in water. Low water levels can cause damage to the pump.

Air In Hot Water Heater

If you seem to notice signs of air in only the hot water lines, it’s likely due to air built up in the water heater, typically caused by sediment buildup. This issue occurs more with well-fed home water systems, which usually create hard water. These microscopic bits of minerals can wreak havoc on the plumbing system and cause trapped air.

Signs There Is Air In Your Hot Water Lines

When you have air buildup in hot water lines, it’s an easy problem to identify. Pipes with trapped air have specific signs that are hard to ignore or misdiagnose.

Irregular Flow

Air in your water lines can cause you to have inconsistent water pressure. For example, you may have a robust and steady gush one moment. And then the next, the water flow slows to a less powerful discharge. You may even hear the pipes gurgle before the water shoots out or have a delay from when you turn on the faucet and the water emerges.

Vibrating Pipes

Pipes that vibrate and rattle are another sign of air in hot water lines. This issue is usually when there is lower pressure.  


If you turn on your faucet and rather than a smooth, steady stream, the water shoots out in a sporadic spew of sputtering and spitting; it’s a guaranteed sign that your lines have trapped air.

How To Fix Air In Hot Water Line

One of the best ways to remove air from the hot water line is by purging or bleeding your water heater. It’s a great idea to perform this task annually (or twice a year for well water systems). Purging your tank must be done correctly. Otherwise, you run the risk of adding more air into the tank. 

Power Off and Let Cool

The first thing you can try to fix air in a hot water line is to shut off the power to the water heater while leaving the cold water on. Wait thirty minutes to an hour so the water in the tank can cool. Make sure none of the taps in the house are turned on during this time, which can add more air to the lines.

Gas-fueled heaters require you to turn off a switch at the bottom of the tank to cut off the feed of the gas, so the pilot light goes out. Electric heaters have to be turned off at the breaker. 

Drain Tank And Refill

Most water tanks have a drain tap at the bottom of the unit. Before opening this to drain the tank, it’s a smart idea to put something underneath to avoid water damage. For example, a tarp or a piece of plastic can protect the floor. 

Next, connect a hose to the sillcock – the threaded valve. Run the hose into a nearby drain or outside. Putting the hose end into a bucket allows you to monitor the watershed for sediment. 

Then open the valve to let the water drain out of the tank. Because the cold water tap is still on, water will continue to fill the tank. This motion will pull out any sediment and trapped air.

Once you notice your water running clear and clean, it means the tank is empty. You can now close the drain valve and refill the tank. Finally, turn the power back on and resume regular use of your heater.

Use Washing Machine

Another way that you can remove air from water lines is by using your washing machine. To use this method, you’ll need to disconnect the water pipes and connect the cold pipe – blue – in the nozzle where the hot water hooks up – the red line. Then open the cold water tap and the hot water and run them for 3 to 5 seconds. You can repeat the process if the issue continues.

Turn Off Water Line And Turn All Faucets On Till Empty

Another thing you can try to remove air from water lines is to bleed your system. Before you can begin with this method, you’ll need to turn off the water supply at the main. You’ll find this valve running from the water main on the street into your home. The valve will be with your water meter. Turn it as far right as it will go.

 Once the water is off, go throughout your home, turning on all of the faucets in your home. Start with the highest floor and work your way down. Do not turn these on entirely, but more of halfway.

A little bit of water will come out of each faucet as the backed-up water in the pipes escapes, along with any built-up air. Once all of the water stops coming out, you can go back to the main and turn it back on (lefty loosey). 

ThenThen you can go back through your house and turn off all the faucets. The water should return to flowing smoothly, without any air trapped inside. 

Replace Any Faulty Piping

If you’ve tried all of these methods to remove the air from your hot water pipes, but nothing is working, the only course of action left is to replace your piping. The most common problem of trapped air is due to blocked valves. Unfortunately, this method can be expensive and messy. If you have no experience in plumbing, you’ll have to rely on a professional plumber to do the repiping for you.


Having air trapped inside the water lines can make for noisy plumbing, inconsistent water flow, and faucets and toilets that sputter and spew water rather than producing a strong gush. We’ve explained the symptoms of air in hot water line and listed multiple methods to fix the issue. We also covered common causes of trapped air in the water pipes.


Submit a Comment

Your email address will not be published. Required fields are marked *