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Noisy Boiler
Hissing or banging noises from your boiler or heating pipes are caused by the following:
Scale in the Heating System
The build up of scale can be treated with a chemical descaler, found at most DIY stores. This involves shutting down the system, adding the product and leaving it to work for a few days. The system then needs to be drained, flushed through and refilled.
This can cause 'hot spots' which produce loud bangs from steam bubbles. This can be treated by adding a chemical descaler to the Feed and Expansion Tank, found at most DIY stores. The system then needs to be drained, flushed through and refilled. See Bleeding Radiators for help with this.
Boiler Thermostat is Set Too High or is Faulty
See Faulty Boiler Controls.
Lack of Water or Pressure in the Central Heating System
You will need to double check that the mains water is on. If it is, first turn off your boiler and check your Feed and Expansion Tank - move its metal arm to release the Float valve if it's stuck. Check that the Open Safety-Vent Pipe is correctly installed. Another cause could be that you have Burst of Frozen Pipes.
If the problem is a lack of water pressure, the pressure indicator on your central heating boiler will usually indicate it needs to be increased.