What a Boiler Kettling Noise Means

A repair technician fixing a boiler.

The rattling or kettling noise a boiler makes is often a cause for distress to homeowners. This not only is a nuisance and affects the comfort of the residents in a home, but it also brings the question of whether the boiler is operating safely and efficiently. There are several reasons why kettling occurs, and it is useful to know them so that it is dealt with appropriately and even prevented in the first place.

Mineral Deposits

Most often, the kettling noise is due to deposits that have built up in the system. It is especially common in regions with hard water. The high level of calcium salts in the water leads to limescale forming on the surface of the boiler kettle. When the water is heated to provide hot water or heating, the lime cannot be dissolved in the warm water and settles at the bottom of the boiler. Additionally, oxide sludge from corroding radiators finds its way. The oxide film that deposits in the boiler is brittle and hard.

The combination of these minerals increases the temperature of the metal of the boiler and can lead to loud bangs, kettling, and loss of boiler efficiency. A slow water flow through the pipes can increase the metal temperature and further contribute to scaling. The mineral deposits will not only affect the efficiency of your heating system but will also decrease the service life of your boiler.

Other Causes for Kettling Sounds

The unpleasant knocking noises from boilers may also be a result of incorrect settings or an inappropriate installation. A faulty boiler stat causes the boiler to overheat. The expanding water in the system ends back up in the heating tank with the fresh cold water and forms sludge. The only way to deal with this is to replace the boiler stat.

A boiler that is too large in view of the total heating space also makes banging noises. Additionally, a pump that has become stuck for some reason or needs replacement can also produce a very loud banging noise.

Boiler Kettling - Protection and Prevention

Even a brand new highly efficient appliance is subjected to the negative effects of mineral deposits. A central heating protector is a good preventive measure as it protects from corrosion and sludge. If mineral deposits have already affected your boiler, the heating system must be treated with special descalers and water softeners depending on the type of boiler and sediment.

Homeowners should not be alarmed by kettling sounds coming from their boiler, in the sense that sometimes the noises can get particularly loud and sound as if the appliance might explode. However, kettling should not be ignored and it is better to prevent it before it occurs. Treatment is often more expensive than prevention and if delayed for too long, it might even decrease the service life of your unit.