How to Fix Air in Hot Water Lines

Updated
Categories Water Heating
If you have air in your hot water line, you need to fix it — here’s how.

Have you noticed a sudden sputtering as you turn on the hot faucet? Air in the hot water line is one common reason. Thankfully, in most cases, it’s straightforward to put right.

Here’s how it happens and exactly how to resolve it.


Air in Water Lines: The Signs

If you suspect air in your line, it should be easy to identify — your faucets will tell you! Here are a few classic telltale signs, which you may want to keep an eye out for:

  • Sputtering: When turning on the supply, the water spits and sputters abruptly.
  • Irregular flow: Air can cause the amount of water to increase or decrease when the faucet is open. There might even be a delay on the supply coming through and you may hear a gurgling sound before it does.
  • Vibrating pipes: Pipes could vibrate at lower pressures.

What Causes Air in the Water Line?

The root of the issue generally depends on the type of water system you have in your home. There’s also the possibility that air could be trapped in both the hot and cold water lines, in which case, you may need different treatments.

Air in the Hot Water Line Only

If you’ve checked your cold water feed and everything seems to be working fine, then the issue generally points towards your water heater.

The process of heating water within a tank can sometimes cause a few air pockets. These can be large or small, but they usually disappear as the water is forced out. The air is also usually found at the top of the tank or high points within your water system.

However, sometimes the air follows the flow. If this is the case, you might notice a few spits at the faucet before the hot water gains a steady flow.

How to Get Rid of Air in the Hot Water Line

There are a few things to try, one of which is by simply running all the taps in your house until the air dissipates. However, purging or bleeding your tank could give you better results. Besides, this is a task which should be done annually — or twice a year if you have a water well system.

You’ll want to make sure you’re purging the air correctly — you don’t want to create the opportunity for more to enter. Here’s how we do it:

1. Shut the Power Off

It’s important to first turn off the power source for the water heater. Refer to your heater model handbook for specific instructions.

2. Let it Cool

Leave the cold water feed on to allow the tank to fill. During this step, you should avoid opening any taps in the house. Doing so will cause more air to enter the system as you drain it.

Take a break

Before moving onto the next step, it’s crucial to leave the tank to cool for between 30 minutes and one hour. Otherwise, you could still have hot water in your line.

3. Locate the Drain Tap

The drain tap is usually located at the bottom of the unit. We suggest you lay some plastic or tarp underneath to prevent any water damage to your flooring. Next, you’ll have to attach a hose to the line and run it into an outside drain.

Take Note

Try to avoid emptying directly into a bucket. This may force you to open and close the faucet frequently — allowing more air to enter the line.
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4. Open the Drain Tap

As you open the drain tap, cold water will continue to enter the tank — remember, the feed is still open. This will force the air plus any sediment out of the tank, so you’ll not only get rid of the air but also any build-ups.

If you do want to check your tank for sediment, place the hose into a bucket (outside) and fill it halfway. Let it sit for a while — the sediment should be visible at the bottom.

Repeat this process until the water runs clean, or you don’t find any sediment in the bucket. The tank should now be drained and flushed through.

5. Fill the Tank

Once the tank is drained, it’s time to refill it. First, you’ll have to close the drain valve to make sure the water stays inside the tank. Only when the tank is full, turn the power back on.

Other Types of Systems

It’s also very common to find air in the cold lines. How it got there and the severity of the problem may depend on your plumbing system. Aside from your water heater, here are some alternatives which could lead to air in both hot and cold lines.

Well-Fed System

With a well-water system, there are potentially three common causes of air in the line.

1. Check Valve

The check valve can be a common issue in well-fed systems and one of the most important issues to look out for. You can usually find this situated near the pump.

One reason is that it may have worked loose and is now sucking in air from the outside. If after inspection you confirm this is the case, a simple hand-tighten could suffice.

Safety first

Call in a professional to recheck the valve to make sure everything is in working order.

If a faulty check valve isn’t spotted and put right, it may well cause a serious problem. When drawing in air, it could also cause contaminants to enter your system. These might be harmful to you and your family’s health (1).

Don’t put it off

If you do suspect a faulty check valve, it’s essential to get it fixed or replaced as soon as possible.

2. Water Level

In a well-fed system, the air is sometimes caused by low water levels — possibly due to overuse or drought.

Luckily, there’s an easy fix to this problem. You can add a few feet of length to the pipe which runs from the pump to the water. It’s best to call in a trained professional to help you out.

3. Methane Gas

Methane is a natural gas and may be found in some areas using well-fed water systems. It does deplete oxygen and in high concentrations can be flammable. Methane gas can also dissolve in water.

As the water is pumped to the surface, the temperature rises while pressure drops. This causes the methane to leak into the water — comparable to how bubbles erupt as you open a can of soda (2).

The most common way to get rid of methane in your well-water is through aeration. Aeration mixes air into the water which then vents the gas out.

Safety first

If you do find traces of methane in your well, check levels regularly to make sure it’s not building up (3).

Gravity-Fed Systems

The cause for air in a gravity-fed system is usually due to the water being shut off because of maintenance. The air can become trapped when the water is suddenly turned on again. You can easily fix this by running your faucets until the water flow becomes regular again.


Keep It Air-Tight

Air in the hot water line can be frustrating. If you suspect the water heater is the issue, look for the signs such as sputtering from the hot faucet only. However, if the cold feed is showing signs too, the problem is likely in your whole system.

Turning on all faucets can help to remove air pockets. Although, if the issue is in your tank, we suggest purging the air out of the system. You can follow our quick guide to help things along.

Has your home been disrupted by air in the hot water line? Have you tried to resolve it and if so, what methods worked for you? We’d love to hear how you got on in the comments section below.

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.
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1 Reader Comment

  1. Jae hudson

    If the handheld sprayer on a kitchen sink is leaking it can cause the kitchen faucet to sputter. Also clogged aerator. Check both if you have sputtering in kitchen only and your sink has a handheld sprayer. Crimping the hose to the spray nosel under the sink can help the problem until the sprayer is replaced.

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