How to Remove Air from Water Pipes and Restore Quiet Flow

By Lee Devlin, Director, Homecure Plumbers
Last updated 12 October 2026

Air in your water pipes makes taps splutter and pipes bang or gurgle. To clear it, turn off the main stopcock, open every tap from the top of the house down, then turn the water back on and close each tap once it runs smoothly.

Air usually gets in after the water has been off, for example after mains repairs in your street. If it keeps coming back, there is a fault in the system and an engineer should take a look.

Signs of air in your water pipes

• Taps that splutter or spit before the water settles into a steady flow.
• Banging, gurgling or knocking from the pipes when you open or close a tap.
• Cloudy or milky water that clears from the bottom of the glass upwards. This is tiny air bubbles.

Why air gets into water pipes

Work on the water mains

When the water company turns off the supply to repair a main, the pipes partly drain and air gets in. When the supply comes back on, that air is pushed through to your taps. Thames Water says water may splutter from taps when it first comes back on and should clear if you run them for a couple of minutes, and that cloudy water from tiny air bubbles clears in the mains within two to three hours. See its advice on what to expect after supply work.

Work on your own plumbing

Draining down to replace a tap, valve or radiator lets air into the pipes. It normally clears once the system is refilled and the taps have been run.

A fault in your hot water or heating system

If air keeps appearing when no work has been done, it is coming from inside the system. Common causes are a small leak, a faulty automatic air vent or valve, or a pump problem on an older open-vented heating system.

How to remove air from water pipes, step by step

1. Switch off a combi boiler if you have one, so it does not try to fire while the water is off.
2. Turn off the main stopcock. It is usually under the kitchen sink, in a downstairs cupboard or where the water pipe enters the house. Turn it clockwise until it stops.
3. Open every tap, starting at the top of the house. Open the hot and cold taps on the top floor first, then work down floor by floor, including any outside tap. Flush each toilet once.
4. Turn the stopcock back on slowly. Water refills the pipes and pushes the air out of the open taps, so expect some spluttering.
5. Close each tap once it runs smoothly, starting with the lowest tap in the house and working up.
6. Switch the boiler back on and run each tap briefly. If any still splutter, repeat the steps.

Air in radiators: bleed them

Air in the heating system collects at the top of radiators and leaves them cold at the top. With the heating off and the radiators cool, open the bleed valve with a radiator key, let the air hiss out and close it as soon as water appears. Bleeding lets water out of the system, so check the boiler pressure gauge afterwards and top the pressure back up if it has dropped.

If the air keeps coming back

Air that returns after you have cleared it is a system fault, not a one-off. It usually means a leak, a faulty air vent or valve, or a pump problem. Book an engineer to find and fix the cause: call 0203 504 4000 or see our plumbing services.

Repairs from £95 + VAT for the first hour, including diagnosis (or a fix if it can be done within the first hour with no parts needed), no callout charge. Prices apply during office hours; parking or the congestion charge may be added.

Pipes still noisy once the air is out?

If the pipes still bang, the cause may be water hammer, loose pipe clips or high water pressure. See noisy pipes: 5 causes and solutions.

Questions about air in water pipes

Is cloudy water from air in the pipes safe?

Cloudy water caused by air bubbles clears from the bottom of the glass upwards if you let it stand. If it does not clear, or the water is brown or smells, contact your water company.

My neighbours have water but I do not. What should I do?

Thames Water says this can be an airlock and asks customers to call it so a technician can attend. Other water companies have similar advice.