You turn the faucet and the plumbing explodes — or so it seems.
Banging, thumping, spluttering, and giving you everything but the water you need.
If this sounds familiar, you probably have air trapped in your pipes.
A little sputtering may seem like a minor nuisance, but air in your plumbing system can stress your pipes, potentially leading to leaks and even damaging your fixtures.
Fortunately, getting the air out — a process called “bleeding the lines” — is a straightforward DIY task that most homeowners can handle without professional assistance.
Why is Air in Pipes a Problem?
You might think air is harmless. It’s just inert gas, right? However, in a pressurized plumbing system designed to carry liquid, pockets of air act like blockages or springs that disrupt the flow.
The Phenomenon of Water Hammer
One of the most common and damaging results of air in pipes is “water hammer.”
- When water moves quickly through a pipe and is abruptly stopped — for example, when a washing machine valve closes — the energy has to dissipate. If air is trapped or if the air chambers intended to absorb this shock are waterlogged, a shockwave travels back through the pipe.
- It creates a loud banging or hammering noise.
- Over time, this shockwave can loosen joints, break pipe connections, and damage valves in appliances like dishwashers and washing machines.
Other Hazards of Trapped Air
- Corrosion: Excess oxygen in metal pipes can accelerate rust and corrosion, shortening the lifespan of your plumbing.
- Reduced Water Flow: Air pockets can reduce water pressure, making showers less enjoyable and appliances less efficient.
- Sputtering Faucets: This can cause splashing and inconsistent water delivery.
Signs You Have Air in Your Plumbing
Here are the clear indicators of air in your plumbing:
- Sputtering Faucets: Water comes out in spurts rather than a steady stream.
- Loud Noises: Banging, clanging, or vibrating sounds when water is turned off or on.
- Low Water Pressure: A noticeable drop in flow rate that isn’t related to a municipal issue.
Common Causes of Air in Pipes
- Plumbing Maintenance: If you recently had work done, air may have entered the system when the water was shut off and pipes were drained.
- Water Main Issues: Sometimes, the municipal supply introduces air during maintenance.
- Well System Issues: If you’re on a well, a failing pump or check valve may be letting air enter the system.
Bleeding Your Plumbing System
Removing trapped air is usually a matter of flushing the system. Follow these steps carefully.
1. Preparation
- Time Required: 15–30 minutes.
- Tools Needed: None.
- Objective: Force the air out by allowing water to flow through all outlets simultaneously.
2. Turn Off the Main Water Supply
Locate your main water shut-off valve. This is typically by the water meter, in the garage, basement, or a utility box near the street. Turn the valve clockwise until it stops to shut off your home’s water supply.
3. Open All Faucets
Start at the top of your house and work your way down.
- Open every faucet in the house — sinks, showers, and bathtubs.
- Turn on both hot and cold handles.
- Don’t forget utility sinks in the garage or laundry room.
- Leave them open all the way.
4. Flush Toilets
Flush every toilet in the house until the tanks are empty. Wait for all water to stop flowing from each tank before continuing.
5. Turn the Water Back On
Return to your main shut-off valve.
- Turn the valve on slowly. You don’t want to send a massive surge of pressure into the system all at once.
- Allow water to flow into the pipes gently so air is not trapped again.
6. Let the Water Run
Go to each open faucet. You may hear sputtering and hissing sounds as water pushes trapped air out of the pipes.
- Start at the lowest faucet in your house (or the one closest to the main water entry point) and wait until the air is gone and the water flows steadily. Then, move upward through each level.
- Let the water run until the sputtering stops and you have a steady, clear stream.
- Turn off each faucet one at a time, starting with the lowest floor and working your way up until all faucets are closed.
7. Close Toilets
Allow the toilet tanks to refill. They should fill quietly and stop at the correct level.
Addressing Water Hammer Specifically
If the bleeding process didn’t stop the banging noises, your issue might be waterlogged air chambers.
Older homes often have vertical pipes installed behind faucets called “air chambers.” These trap air to act as a cushion for water pressure. Over time, the air dissolves into the water, and the chamber fills with liquid, losing its cushioning ability.
To fix waterlogged air chambers:
- Shut off the main water valve.
- Open the highest and lowest faucets in the house to drain all water from the pipes.
- Once the pipes are fully drained, the air chambers will fill with air again.
- Close the lowest faucet and turn the main water supply back on.
- Air remains trapped in the chambers (where you want it) while water fills the rest of the pipes.
Note: Most newer homes have water hammer arrestors installed on their lines.
When to Call a Professional
Some symptoms require an expert.
- Persistent Noise: If the banging continues after you’ve bled the lines and refilled air chambers. You may need to install mechanical water hammer arrestors.
- Well Issues: If you’re on a well and air returns constantly, you may have a pump issue or a leak in the drop pipe. This requires specialized repair.
- Leaks: If water spots on ceilings or walls accompany the noise.
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- Check Shut-off Valves: Ensure your main shut-off valve works properly so you can perform this maintenance easily.
- Inspect Appliances: Check connections to washing machines and dishwashers regularly.
- Monitor Pressure: High water pressure can exacerbate air issues and water hammer. Consider installing a pressure-reducing valve if your pressure exceeds 60 psi.
FAQs: Air in Pipes
Q: Can air in pipes cause a pipe to burst?
While the air itself isn’t the problem, the resulting water hammer creates shockwaves. These pressure spikes can weaken joints and pipes over time, eventually leading to bursts or leaks.
Q: Why does my hot water sputter but not the cold?
This usually indicates an issue with the water heater. Air can become trapped at the top of the tank, or the anode rod may be corroding and producing hydrogen gas. If bleeding the hot water lines doesn’t work, have your water heater inspected.
Q: How long should I let the water run to bleed the pipes?
Usually, 5 to 10 minutes is sufficient. You only need to run it until the water flows steadily without sputtering or hissing.
Q: Do I need to open outside spigots?
It’s helpful to open outside spigots (hose bibs), especially if they’re lower than the faucets inside the house. This ensures the system drains completely.
Q: What is a water hammer arrestor?
It’s a small device containing a piston or diaphragm and a chamber of air/gas. It installs onto your pipes (usually near washing machines) to absorb the shock of stopping water, replacing the function of old-fashioned air chambers.
Q: Is it safe to drink cloudy water caused by air?
Yes. If you fill a glass, and it looks milky but clears up after a minute (clearing from the bottom up), it is just tiny air bubbles. It’s safe to drink, although you usually want to address the underlying issue for the sake of your pipes.
Q: Does bleeding radiators fix air in water pipes?
No. Radiators are part of a closed heating system (boiler). Bleeding a radiator releases air from the heating loop, which is separate from your domestic water supply (faucets/showers).
Q: Will air in pipes go away on its own?
Sometimes, small amounts of air will escape through normal use. However, significant pockets causing water hammer or sputtering usually require the flushing process described above.
