My Radiator Making Bubbling Noise?

When the pump starts to drive water through your home’s many pipes, a pocket of air can forms as water flows over or between irregular surfaces in a radiator. That can produce a gurgling or bubbling sound. This is worth checking with a trained professional or your central heating insurance provider and it can indicate sludge accumulation. More on this below.


If your radiators are deemed fine, it could be that your boiler’s pump speed is too high, which could lead to these sounds. An auto bleed which automatically removes air could be a good investment. Make sure to have the piping to the radiators and the area around their valves inspected for possible water leakage.

Also, when “bleeding” radiators, it is worth letting the water flow a bit to be sure all the air possible has been removed. If this does not happen, gently wriggle the radiator a bit and any more air is released. If the radiators need to bled often, it is usually an indicator of an issue with the expansion tank or elsewhere. To rectify this, it is worth speaking to a professional about adding anti-corrosion inhibitors after repair of the leak to ensure no repeats and no surprises.

How to stop it

Removing limescale

If you have a noisy boiler this may be indicative of limescale having reached levels that can potentially jeopardise the proper functioning of your boiler’s heat exchanger. This is because limescale is a long-term occupier in the system that restricts the water flow. The restricted water flows within the heat exchanger can get excessively warm. As this water begins to climb past 100 degrees celsius, then steaming and expanding, the system will be making those familiar sounds. This is well known in older heating systems. To rectify, the installation of a descaler for the feed and expansion tank could be well worth it. Once the descaler has been working for a few hours, it is recommended to flush the central heating system with clean water and add some radiator inhibitors, to help prevent corrosion (more below).

Eliminating the limescale build-up will bring an end to the noise, but it will also maximise the longevity and efficiency of the appliance by allowing water to pass with greater ease.

Flow Rate

Any strange noises in the boiler system could the result of reduced water flow. Contemporary gas boilers demand a particular flow rate for good functioning. If not, it can be a useful starting place for diagnosis of the noises. The required flow rate should be in the manufacturer’s notes or manual.

Sludge and Debris

Without regular annual service, a boiler can become appreciably noisier. This may be more frequent when the hot water is in use. A Magna clean can be magnificent to help eliminate sludge and debris; these are also good for reducing the home’s carbon footprint when installed with an auto bleed valve.

Dial-up the water pressure

In some cases, the central heating requires an added boost to circulate air out of radiators. Make sure your circulation pumps are working, increase water pressure to two bars, and then bleed radiators once more.

Check the pumping system

Does a vent show on the gas boiler pump’s suction side or not? Is your pump speed right, or is it too high? To answer these questions accurately, a Gas Safe-registered professional will be needed. It is possible to decrease the pump speed on your own. If the strange sounds stop when the pump is off, then it may just be the case that you have isolated the problem – fixing it for good could be the more onerous job.

As ever, do not attempt to repair if you are uncertain of what it involves. If a repair involves taking a gas boiler cover off, then it is too complicated for the unqualified. Get in touch with a trusty local technician.

To prevent bubbling or gurgling systems

Water Softening

To prevent noises, ensure that hard water does not pass through your central heating system. The installation of a water softener will pay dividends, replacing hard, mineral-rich water particles for safe sodium particles. This will drastically slowdown limescale accumulation.

Electrolytic scale reducers

Limescale build-up can also be slowed down with an electrolytic scale reducer. This less expensive substitute to a water softener is nevertheless trusty means of prevention with noisy boilers.


Why should I get electrolytic scale reducers?

Some of Britain’s biggest cities are within hard water regions. In fact, most of England is subjected to water hardness levels that exceed 200 parts per million (ppm).

The ‘hardness’ of the water depends on local geology and rock formations that will determine the mineral content of the water used for your radiators. As the groundwater runs over the stone it absorbs calcium and creates ‘hard water’ which contains at least 200 and 300mg of calcium carbonate per litre. As we know this hard water leads to limescale within our water systems. Even though the presence of limescale within a heating system cannot be detected by the naked eye, its existence is real and harmful.

The problem of ‘kettling’ or this rumbling sound caused by limescale accumulation is very real. For this reason, Part L of the Building Regulations advises that where hard water exceeds 200ppm there should be some provision to fix the feed water to water heaters and the hot water circuit of combination boilers as to reduce the rate of limescale build-up.

Two main types of scale reducer exist on the market. Magnetic scale reducers prevent the build-up with magnetic principles, acting as a water conditioner. These devices offer single appliance protection and are ideal for showerheads and kettles, and ensure that should any scale reform – it is far easier to remove. Electrolytic scale reducers provide protection for your whole property by changing the structure of the limescale that forms, preventing it from strongly adhering to the pipework and key components of the heating system.