The heating makes noises – examples, causes and measures

In case of these or similar water noises, there is probably air in the heating system. The radiator should be bled. You can easily do this yourself, even without a heating engineer. All you need for this is a vessel to catch water, a rag or cloth, and a bleed key, which can be bought at a DIY shop or a specialist shop. Once you have gathered everything, simply follow the step-by-step instructions below to bleed your radiators.

Step by step: bleeding the heating system correctly

1.  Switch off the heating circuit pump
2.  Open all thermostats
3.  Place a cloth underneath or wrap it around
4.  Position the bleed key on the air vent valve (usually on the side opposite the thermostat) and hold the vessel under it
5.  Turn slowly and let the air escape
6.  As soon as water escapes, close the bleed valve
7.  Restart the heating circuit pump
8.  Ensure that the water pressure is sufficient: if necessary, contact a heating contractor who will top up the system in accordance with VDI 2035, depending on the regional water quality

If there is noticeable gushing noise from the heating system, the circulation pump is most likely set too high. This means that a lot of water is flowing through the system. The gushing noise in the pipes is correspondingly louder. The appropriate setting differs depending on the demand of the heating system. Therefore, a contractor should always be contacted.

Have you carried out renovation work? If the heat demand of your house has changed as a result, the heating contractor will usually carry out hydronic balancing. During hydronic balancing, the heating engineer checks the entire heating system to ensure that the heat distribution in the house is correct. This can also eliminate annoying gushing noise.

A knocking or cracking noise in the radiators or in the wall initially has a disconcerting effect on many people. In fact, the cause can often be traced back to the brackets for the hot water pipes. Hot water causes pipes to expand. If they do not have enough space for this in their wall brackets, this can cause eerie noises. In this case, a heating contractor should replace the brackets and/or re-insulate the water pipes.

The heating system may also make cracking noises if the pipes are not installed free of tension. The often difficult task of identifying the relevant location should be undertaken by a heating contractor. Ideally, they will also know the sustainable and effective solution to the "crackly" problem.

If the heating system makes knocking noises, a missing or improperly adjusted overflow valve may also be the cause. In older systems, it may be responsible for excessive pressure in the heating system. Call in a heating contractor. They will take a closer look at the valve, which is located above the circulation pump, and readjust it if necessary.

A humming noise from the heating system often occurs directly at the thermostatic radiator valve. In this case, the heating circuit pump is probably set too high and produces the humming noises after the thermostat is turned up. If the heating system is well adjusted by hydronic balancing but still hums, this may be due to an old heating circuit pump. A heating contractor will determine the exact cause and replace or clean outdated or contaminated components.