Typically, the boilers are noisy appliances. But any noises that make your home feel like a haunted house should be cause for concern. Taking quick action safeguards your hot showers, extends the boiler’s lifespan, and saves you a small fortune.

We’ve created a detailed guide to help you get to the root cause and fix the problem quickly and efficiently.

10 Common Boiler Noises

1.  Dripping Noises

You’ll hear dripping noises if your boiler somehow springs an internal leak. Naturally, it’s best to have an expert inspect your unit sooner than later. An internal leak in a boiler may wreck the boiler’s electrical components. If the water gets to the boiler’s Printed Circuit Board, you’re likely to incur a hefty repair bill.

Common Causes of Boiler Leaks

An internal leak in a boiler may result from various issues, including:

• Corrosion: Heat exchangers (aff link to Amazon) are prone to corrosion.
• Wear and tear: Worn seals and gaskets lose their integrity.
• High boiler pressure: High pressure leads to pinhole leaks that get bigger with time.

 Fixing a Boiler with Dripping Noises

Water leaks in a boiler are a severe problem that warrants calling a professional. Have a boiler engineer inspect and repair the unit to avoid further damage. If the PCB is damaged, you might consider replacing the unit as it might prove too expensive to repair.

2.  Rattling Noises

If you hear loud rattling noises coming from your boiler, it could indicate the presence of loose objects. There maybe loose objects rubbing against each other or shaking in the boiler.

The rattling noise could result from air being trapped in the pipework. The noise could also stem from a few loose valves on the radiators. You might also hear the annoying rattling noise if there are unclipped pipes in your central heating system.

Finally, rattling noises in a boiler often result from a faulty boiler pump or valve. In most cases, the noise stems from a failing non-return valve.

Fixing Rattling Boiler Noises

Check for loose pipes and piping connections in your system and tighten them with a screwdriver. If that doesn’t fix the problem, you should try bleeding your radiator. Be sure to re-pressurize the radiator after bleeding to restore the correct water pressure. Check your system for any unclipped pipes and clip them properly if that fails.

If all else fails, bring in a professional repairman if your boiler still produces rattling noises. You could be dealing with a faulty boiler valve or pump, which requires specialized skills and knowledge to fix.

3.  Loud Humming Boiler Noises

If running an electric water boiler, you may notice loud noises if the heating element comes loose. The humming noise may also result from limescale, rust, or sediment buildup on the water heater.

A boiler is likely to make vibrating noises in some instances because of high water pressure. If the water pressure in the main supply line is very high, it causes the water valves to hum or whine. You’d need to adjust the water pressure to fix this problem.

In other cases, your boiler could be producing humming noise because the pump is set too high. When your pump is set too high, it forces the hot water through the pipes at high speed. When the water travels too fast through the plumbing lines, it sets of several issues, including trickling, vibrations, and humming noises.

Still, your boiler may produce a humming noise because of a faulty fan. The noise often results from worn bearings in the fan.

Fixing Humming Noises in a Boiler

• Check for vibrations: If the boiler hums and vibrates when it’s running, it is not secured correctly. Tighten the existing boiler brackets or have a technician install new ones.
• Remove the debris and limescale buildup: Flush out the system with a central heating inhibitor to dislodge the sludge. Alternatively, you may perform a power flush to eliminate limescale and debris buildup. Installing a limescale reducer is wise for people living in hardwater areas.
• Lower the water pressure: Installing a water pressure regulator helps normalize the water pressure in your home. The ideal water pressure in a home is 40 to 60 PSI. High water pressure above 80 PSI may damage your entire plumbing system.
• Lower the pump speed: Check if the pump speed is too high and set it to the correct speed.
• Replace the faulty fan: If none of these fixes solves the problem, have a technician diagnose the problem and replace any defective fan bearings.

4.  Vibrating or whooshing Noises

If your boiler is emitting whooshing sounds or vibrating, you could have one of three problems:

• Faulty boiler pump: A pump may malfunction and produce a vibrating sound if it comes off its mountings, causing it to move around the casing. In some cases, the pump might be set at high speed and pushes the water through the pipes too quickly.
• High water pressure: If the water pressure in a boiler exceeds 2.5 bars, it causes the valves inside your home plumbing to vibrate and hum.
• Blocked air intake: Sometimes, the flue, which extends outside your home, is blocked by debris, feathers, and leaves. The blockage in the air intake creates a humming or vibrating noise.

Fixing Vibrating Noises in a Boiler

• Check the boiler pump: Ensure the pump is well-secured in its casing and not moving around. Check the pump speed and ensure it’s set at the correct rate.
• Check the boiler pressure: The pressure gauge at the front of your boiler should read below 1.5 bars when the radiators are cold. The ideal pressure inside a hot boiler is about 2 bars. If the pressure rises rapidly to 3 bars, you should consult an engineer.
• Clear the air intake: Check the flue for obstructions and ensure it’s clear of any foreign objects, debris, or grime. You should detect air movement by placing your hand over the intake of a clear vent.

5. Whistling Boiler Noises

If your boiler is emitting whistling sounds, you could be dealing with one of two issues. There could be air trapped in your central heating system, or you have a kettling problem. Kettling is a boiler noise that resembles a whistling kettle, only much louder and annoying.

The noise results from a sludge and limescale buildup inside the boiler and is typical in hard water areas. A debris buildup at the bottom of the boiler narrows the passage, trapping the water and restricting flow. That causes the water to steam, boil, and expand, producing the characteristic kettle sound.

A whistling boiler is not only annoying but also lowers your central heating system’s efficiency. You’ll notice reduced hot water flow from your tap and a sudden spike in your heating bills. Still, kettling accelerates the wear and tear of your boiler. Therefore, you should have an expert fix the problem quickly to avoid a costly replacement.

Fixing Whistling Boiler Noises

Quick diagnosis. Check if the noise results from air trapped inside the radiator. The most obvious sign to look for is a radiator that stays cool even when the central heating system is running.

Other common signs include cold spots at the top of the radiator due to air rising to the top. Condensation buildup or damp patches above the radiator are also common.

• Bleed your radiator: Air buildup is a common and expected boiler problem with an easy fix. Boilers have an inbuilt radiator bleed valve. Insert the radiator key into the bleed valve and give it a quarter turn to release the trapped. Close the valve once the hissing noise stops and water starts coming out.
• Kettling: If bleeding the radiator doesn’t fix a whistling boiler problem, you’re dealing with a kettling problem. Unfortunately, this is a complex problem that requires the skills and expertise of a trained engineer. You’re better off calling in an expert service to fix a kettling boiler problem.

6.  Banging Noises

If your boiler makes loud banging noises, like an untalented kid in a band practice, you could also have a kettling problem. Loud banging or popping noises in a boiler are often caused by mineral deposits or sludge buildup in the heat exchanger.

Sludge and mineral deposits are more common in boilers with the older cast-iron heat exchangers, especially in hard water areas. The noises result when the buildup creates a choke point that restricts or blocks water flow into the heat exchanger. Kettling causes the water to boil and steam, producing the whistling sounds alongside the characteristic banging sounds.

Large air bubbles start popping in severe kettling cases, creating loud banging sounds. Typically, a boiler doesn’t boil the water but heats it to about 70 °C. The presence of steam in the system results in annoying banging noises.

Banging noises can also indicate an overheating boiler due to the wrong temperature setting or a faulty boiler thermostat.

Loosened pipework may also cause banging loud noises in your boiler. The constant heating of cold water causes the pipes to contract and expand, placing a lot of stress on the plumbing. Loose plumbing lines under the floorboard may have plenty of play as the hot water flows through them, creating a banging noise.

Fixing Banging Boiler Noises

• Check the pipe connections: Check and fix any loose pipe connections in your plumbing system.
• Flush the system to remove the limescale and debris buildup
• Replace the faulty thermostat: Install a new thermostat and ensure it’s set at the correct temperature to avoid overheating the water.

7.  Gurgling Boiler Noises

A constant, loud gurgling noise from your radiator points to one of three things: low water pressure, trapped air, or there’s frozen condensate in the pipes. Luckily, there as simple fixes to each of these problems.

• Bleed the radiator: Bleeding the radiator is the universal fix for air trapped in the radiator.
• Low water pressure: Look at the water pressure gauge attached to the front of your boiler. Typically, any reading below 1 bar is indicative of a low-pressure problem. Most boilers will display a warning when the water pressure drops. You need to re-pressure the boiler and reset it to the correct pressure. You can re-pressure a boiler using a filling loop or a pressure key. The process varies between boiler models, so consult your boiler manual.
• Check for frozen pipes: Locate the frozen condensate or overflow pipe. It’s usually located outside the house. Use some warm water to thaw the ice to let the air escape from the boiler.

8.  Tapping Noises

If you hear tapping noises whenever you turn on the boiler, you could be dealing with a kettling problem. The tapping noise results from the localized water boiling and turning into steam. The tapping sounds get louder as the water is pumped through your central heating system. Trapped air bubbles in the circulating water expand and collapse as it moves around your central heating system, producing the tapping sound. Call a boiler engineer to fix this problem.

Fixing Tapping Boiler Noises

• Power flush your system to remove limescale, rust, and debris buildup
• Check your boiler’s thermostat: Turn off the boiler and leave it to cool off for several hours. Switch on the cold boiler and listen for a clicking sound. If you don’t hear the sound, have a technician replace the faulty thermostat.
• Check the pipework: Check any loose connections in the plumbing system and secure them firmly to the walls.

9.  Drone Noises

If you notice your boiler emitting noises that resemble a foghorn, drone, or an airplane, you have a severe problem. Such noises point to a faulty boiler pump and require immediate attention. The issues could range from mechanical failure to debris buildup in the boiler’s impeller.

Left unattended, a faulty boiler pump can cause your boiler to suffer extensive damages. If you don’t catch it on time, you may have to replace your boiler. The cost of repair may outstrip the cost of buying a new unit.

Fixing Drone Boiler Noises

Have an experienced boiler engineer examine the unit and repair or replace the unit. Given the complexity of fixing or replacing a boiler pump, you’re better off letting a professional fix the problem. Replace the old unit with an efficient, modern model to avoid costly repairs.

10.  Clicking Noises

You’re likely to hear clicking noises if your boiler has an ignition problem. Boilers fail to ignite due to faulty valves and thermocouples (here’s a replacement on Amazon) low pressure, dirty pilot light(aff Amazon link) or they’re out of gas.

Fixing Clicking Noises

• Clean the pilot light with a wire brush or a cloth
• Have a technician replace faulty thermocouples and valves and check the unit for pin leaks.
• Check your monthly gas bill. If you notice a sudden spike in gas charges, you could be dealing with a gas leak.

How to Power Flush Your Boiler

A power flush is a popular way to clean a central heating system. It entails forcing high volumes of water and cleaning agents into your heating system to remove rust, debris, and mineral deposits. You need a power flushing pump to flush out your system.

1. Switch off your boiler
2. Close the isolating valves on either side of the heating pump.
3. Remove the pump from the boiler
4. Connect the power flusher to your central heating system
5. Switch off the radiator valve. Disconnect one of the radiator valves but keep the air bleed valve open.
6. Drain all the water from the radiator
7. Connect the power flusher to the return valves on your central heating system.
8. If you have an open vented system, turn off the mains valve. If you have a sealed system, drain some water to depressurize the system.
9. Add your cleaning fluid to the power flusher.

• Ensure all radiator valves are open and run the power flusher
• Run the boiler to circulate the chemicals but turn it off when the water temperature gets to 45°
• Reverse the water flow from the power flusher every 10 minutes
• Close all radiator valves but leave one open to flush it and repeat the process with each radiator in your system
• Open all radiators to let the flush flow through them all freely
• Add a neutralizing agent to neutralize the cleaning agents
• Flush the system one more time before adding a corrosion inhibitor
• Close all the valves and disconnect the power flushing unit
• Reconnect all the central heating system items and turn on the water mains

How to Bleed a Radiator

1. Turn on the central heating unit and allow the radiators sufficient time to warm up.
2. Do the touch test to determine which radiators need bleeding. You’ll need to bleed any radiator with a cold spot or produce a gurgling noise.
3. Turn off central heating and give the radiators time to cool down.
4. Locate the bleed valve. A typical bleed valve is a round hole with a square on the inside and is usually located on the top corner of the radiator.
5. Place an old towel or a container below the bleed valve to catch any water spilling over.
6. Open the bleed valve and release the trapped air. Use the radiator key to open the bleed valve by turning it slow for a quarter turn.
7. Close the bleed valve. Wait until the hissing sound stops and some water starts to leak out to close the valve.
8. Repeat the process with every radiator that needs bleeding, and the annoying noises will fade away. Check the pressure on each radiator and keep the pressure between 1 and 2 bars. If the pressure falls below one bar, you may need to re-pressurize the system.

Bottom Line

If your boiler is making loud noises, it’s probably trying to get your attention. The loud noises amount to a cry for help. A noisy boiler is trying to explain what’s wrong and what kind of help it needs. This guide can help you diagnose the most common boiler noises so you can take corrective action and bring it back to normal function.