What are some common causes for a noisy central heating system?

There are several factors that can cause a noisy central heating system, some of which can be easily fixed.

On this help page, we will cover various sounds that your central heating system may produce and provide solutions to eliminate the noise.

Is your central heating system making any of the noises below and causing a disturbance?

• Clicking
• Humming
• Tapping
• Gurgling
• Knocking
• Creaking

Continue reading to find out why, and the steps you can take to resolve the problem.

What is the cause of the noise?

Your central heating system is mostly made up of metal components, and metal expands and contracts as it heats up and cools down. Your central heating may naturally produce sounds as a result of this process.

Expanding and contracting pipework often makes noise. However, if you notice unusual sounds from your central heating system, it's best to address it as soon as possible.

If your central heating is making loud and irritating noises, it's important to have it thoroughly checked and repaired by a qualified heating engineer.

With the help of this guide, you will be able to identify and resolve common causes of noisy heating systems without having to spend a lot of money on repairs.

My central heating is gurgling. What is causing it?

You may be able to hear a gurgling sound that resembles a kettle as it starts to boil. Often the cause for this is not the boiler itself but can be the pipes or radiators; this could be down to a few common causes.

Most frequently, the cause of a noisy radiator is air being trapped inside the system. If this is the case, it is recommended to fix this issue as soon as you can.

Noise coming from the radiator is not the only sign of this problem. If you also find your radiator feels hot at the bottom, but cold at the top then there is air trapped inside. The solution to this is to bleed your radiators, you can find out how to do this with our guide below:

How to bleed a radiator

If you find you can hear noisy pipes (especially during colder weather) this could be down to a frozen condensate pipe. In particularly cold weather pipes can freeze, this then causes a blockage and stops water from moving freely through the system.

The condensate pipe is located on the exterior of the building, it is normally a white overflow pipe that carries waste water. If the condensate pipe is the issue and has frozen, it is most likely frozen near the drain towards the end of the pipework.

Fill up a measuring jug or something similar with warm water. Water must not be too hot or this can cause damage to the pipe. Now pour water slowly onto the outside of the pipe, this will usually resolve the issue. Once the blockage is cleared, finish the process by restarting your boiler.

Why is there a tapping noise coming from my central heating?

A tapping sound can be a sign that there is a build-up of limescale in the pipes and radiators.

One solution to this is to turn off your heating, and then flush the system with a non-acidic cleaner. If you have an older central heating system, you may need a stronger solution. Your local plumbers merchant will be able to advise on which type of chemical cleaner to use based on the age and condition of your central heating system.

What is the cause for my central heating humming?

Your immersion heater has heating elements, a sign that they may not be functioning properly can be a humming sound. Firstly, begin by checking that the thermostat is working normally. If the thermostat seems fine, then check the central heating pump to see if it’s set too fast, as it may need slowing down.

Is your boiler noisy?

It’s normal for boilers to make gurgling noises, so often it isn’t something to worry about.

However, if your boiler is making unusual noises that are louder than usual then it’s best to check it over and see if anything needs adjusting.

Below you can find a few ways that can help to resolve a noisy boiler.

• Check the flow rate of your boiler, a low water flow in the system can be a cause of the noise. (The correct flow rate can usually be found in the manual) If this is the issue, keeping it at the correct level will make the boiler function more quietly.

• Limescale can also be a factor that can cause a loud boiler. If when the boiler comes on it’s making a sound resembling a kettle as it starts to boil, then this is likely down to limescale. To clear the limescale, you can add de-scaler to your feed and expansion tank. Once the system has been fully saturated, the system will then need to be flushed with clean water. Finally, add some radiator inhibitor. This will help prevent corrosion. By following these steps, not only will your boiler be less noisy, but it will also have a longer lifespan and increased efficiency.

One preventative measure you can take is to install a water softener near your main water supply, this will protect your system from the limescale that can occur due to hard water.

Alternatively, a cheaper option is to install an electrolytic scale reducer. It works by altering the structure of the hardness salts, inducing coagulation. This provides benefits to a range of appliances from kettles to showers and boilers, offering protection for your whole house against scale.

• Debris and sludge can build up causing your boiler to become louder. It is advised that you have your boiler serviced annually, which will help to prevent this.

Do your pipes make a banging sound?

You may have noticed that when turning on your taps in the bathroom you hear banging noises. This is called water hammering, it can occur for a number of reasons. Commonly it is due to pipework not being secured properly, it can also be caused by air in the system, or overheating.

If this is the case for you, you should start by checking your thermostat.

• Before starting, turn your boiler off and let the system cool down.
• Once it has been switched off and cooled down, turn your heating back on and turn up the thermostat high. A loud click should occur when you do this, but if not, call an engineer to diagnose the issue.

• Alternatively, the noise could be due to pipes that have not been secured properly, causing them to rattle. A simple solution to resolve this is to push some felt into gaps around the pipe in areas it may rattle against when in use. Ensuring it is snug and doesn’t have room to move around.

What is the cause of my central heating knocking?

When the system's water heats up, the pipes expand, they then contract once they cool.

Noises can occur if there isn't enough room beneath the floorboards for this to occur.

If you find that the pipes are positioned too close to the floorboards or joists, you can use a saw or a chisel to make more room in the areas required.

When the pipes have room to expand but are still making noise, pack some light insulation around them to limit movement.

Is the noise coming from my central heating pump?

In the winter, noisy heating pumps are common as they go into defrost mode. The heat pump may make a swooshing noise as the internal valves shift into winter mode.

Frequently, central heating pump issues are the cause of boiler problems. When a hot water pump isn’t functioning as it should do, it can lead to a noisy boiler, leaks, or even stop your radiators from working as they should.

If you believe that there is unusual noise coming from your central heating pump you can take the steps below to see if it’s something you can resolve yourself.

• Make sure your central heating pump is securely in place. By using brackets to firmly secure it, it will prevent vibration of the boiler unit itself.

• Check the heat pump fan – Sometimes they can make a clanking noise that resembles metal clashing together. Fully turn off the boiler pump and wait for the fan to stop spinning. Now check the blades turn without catching on something they shouldn’t, it can be as simple as something coming loose and hitting the fan when turned on.

• Bleed the central heating pump – Trapped air can also be an issue that affects the heat pump. Much like bleeding a radiator, you should locate the bleed valve, and turn it around halfway. Be sure to have a tea towel to hand as once you have let the air out there may be some water leakage.

• Adjust the speed of the central heating pump – It is fairly straight forward to turn the speed of the pump down, they usually have 3 speed settings. 1 is the slowest speed and 3 being the highest. Bear in mind that by having it on the lower speed your radiators may take longer to heat up. So if the issue continues despite trying all of the above, contact a qualified heating engineer.