Boilers: Why Do Radiators Make Noise When Turned On?
There is nothing like a warm home during the winter months; however, strange noises coming from your radiators when you turn on your boiler can disrupt this peace. Rattling, gurgling, or a deep humming... These sounds are not just an annoying noise, but can also be signals that something is not right with your system.
COPA service experts have summarized the causes of radiator noises and how to resolve these situations for you.
1. Gurgling and Air Noises
If you hear a water sound similar to an aquarium or a sound as if air is being discharged from your radiators, the most common cause is air in the system.
• Why Does It Happen? Air bubbles that emerge during the filling of the installation or as the water heats up become trapped in the upper parts of the radiators. This situation not only creates noise but also causes the upper part of the radiator to remain cold.
• Solution: You should bleed the air by loosening the bleed valve on the upper side of the radiator using a radiator key or a flat-head screwdriver. You can close the valve once the water starts flowing steadily.
2. Metallic Clicking Noises
"Click-clack" sounds, heard especially when the boiler first starts operating or when it shuts down, are usually caused by expansion.
• Why Does It Happen? Heating metal expands, and cooling metal contracts. If the mounting brackets (consoles) fixing the radiators to the wall are too tight, or if the pipes are too tense at wall crossings, the movement of the metal creates this friction noise.
• Solution: This noise is generally harmless. However, if it is very severe, the noise can be reduced by fitting plastic protectors to the radiator brackets or by loosening the connections.
3. Humming and Whistling Noises
If a constant humming or whistling sound is coming from the radiators, the problem is usually related to the water flow rate.
• Why Does It Happen? Your boiler's circulation pump might be running at a higher speed than necessary, or the water pressure in the installation is too high. Additionally, calcification on the pin tips of thermostatic valves causes water passing through narrow spaces to whistle.
• Solution: The boiler pump speed should be adjusted, and it must be ensured that the water pressure is between 1.5 - 2 bar.
4. Knocking and Sharp Impact Noises
Sharp impact noises (water hammer effect) coming from the radiators while the boiler is running are usually caused by installation errors.
• Why Does It Happen? Reversely connected valves or unsuitable installation pipe diameters cause the water to create severe turbulence while changing direction.
• Solution: This situation requires a professional technical inspection. The direction of the valves and the installation connections must be checked.
5. Friction and Sludge Noises
If the noise sounds more like something rubbing or sand grains colliding, it may be time to clean your installation.
• Why Does It Happen? Lime, sediment, and sludge forming in the installation water over the years make the water flow difficult and create noise.
• Solution: This problem can be eliminated through installation flushing and the use of protective chemicals (conditioning).
💡 Expert Advice Although noises from radiators are often solved with a simple air bleeding process, persistent and increasing noises can shorten the lifespan of your boiler. COPA high-efficiency heating systems offer quiet and comfortable operation with correct installation and regular maintenance.
If you cannot identify the source of the noise, we recommend seeking support from a professional without damaging your system.
To discover quiet and efficient heating solutions for your home, you can browse our Products section.