• Many central heating systems generate a small amount of noise, with most of the components that make up the pipework and associated infrastructure being made of metal, there will always be a certain amount of noise as the metal expands and contracts as it heats up or cools.Louder and more persistent noises may need to be investigated by a qualified plumber.

    The following are some typical noises that your central heating may be making.
  • 1. Noisy central heating system
    If your central heating system is making unusual noises, there are several things that may be causing them. The system may be low on water. If you have an open system, you can check on the feed and expansion tank usually located in the loft space. The water level is controlled by a ball valve similar to the cistern in the toilet, so if the water level seems a little low you can gently press down the ball until enough water has raised the level.If you have a sealed system, you may need to increase the boiler pressure. Most heating systems run at a pressure of between 1 and 1.5 bar (check your boiler handbook for specific pressure).

    A build up of sludge (a mixture of rust and limescale) can build up in your system over time, this can cause gurgling. Badly fitted pipes can cause banging as the pipes expand when they get hotter. Have a look at the symptoms below and see if they help, if they don't, contact us to arrange for an engineer visit.
  • 2. Pipes banging and knocking
    The problem may be with the thermostat. Turn the heating off, adjust the thermostat down and wait for the system to cool. When the system has cooled down, turn the system back on again and turn the thermostat up to the maximum. If you don't hear the thermostat 'click' then you will need to contact us and we will arrange for an engineer to visit.

    Alternatively if you hear banging from your pipes when you run the hot water tap, it may mean the pipes haven't been secured correctly. To eliminate the noise, wrap some felt around the pipes where they come into contact with the supporting beams and woodwork. You may have to enlarge the gaps between the pipes and the woodwork.
  • 3. Heating system 'gurgling' — bleed radiators
    Gurgling sounds coming from your heating system could be caused by trapped air. This prevents the hot water reaching all parts of the radiators as well as the annoying noises. The air can be released easily using a radiator bleed key (for more information see the Cold spots on radiators: how to bleed your radiators topic).
    • Locate the bleed key into the bleed valve (located at the top of the radiator either left or right)
    • Give the key a half turn anti-clockwise
    • Any trapped air will escape
    • When water starts to dribble from the valve
    • Turn the key a half turn clockwise
    • Your system may need to be repressurised, if your boiler has a pressure guage ensure it's running between 1 and 1.5 bar
    If the heating system still 'gurgles', there may be air trapped elsewhere, try bleeding the other radiators in the house.
  • 4. Heating system 'gurgling' — blocked condensate pipe
    Another cause of 'gurgle' noises in your heating system may be that the condensate pipe is blocked (for more information see the Preventing a frozen condensate pipe topic). If your boiler has shut down and is showing error code F28 or F29, then your condensate pipe may be frozen. If the weather outside is cold and the condensate pipe hasn't been lagged, the condensate pipe may be frozen.
    • Run your hand along the condensate pipe and see if you can feel any cold spots
    • Pour warm (not boiling hot — this could split the pipe) along the cold area. Alternatively put a heating pad or hot water bottle against the pipe to thaw it out.
    If this doesn't cure the problem please contact us.
  • 5. Heating system tapping
    If your heating system is tapping and/or gurgling, it may be caused by a build up of sludge made up of limescale and iron oxide (rust). Clearing the system of this sludge will require the system to be flushed with a system cleaner and a volume of water sufficient to wash away as much of the sludge as possible.

    This is best done by a professional, contact us for advice.
  • 6. If you have misplaced or lost your user manual, you can locate a replacement manual from this list of Vaillant boilers (please have your model number to hand).
  • We update the maintenance tips and troubleshooting guidance from time to time and aim to make it as helpful as possible. The purpose of the maintenance and troubleshooting section of this website is to provide you with general guidance. Please ensure you read and follow our instructions carefully and do not undertake the maintenance or troubleshooting unless you are aged 18 or over, are competent to do so and are confident that you can complete the maintenance. If in doubt do not attempt any actions and where an appliance is gas fuelled refer to a Gas Safe engineer for assistance.

    This website is not intended to be a substitute for professional advice and does not:
    - cover every reason that your product could fail;
    - cover all of the maintenance that can be undertaken for your product;
    - supersede any advice in your instruction manual or from your product manufacturer.

    Do not carry out any maintenance or use the troubleshooting guide if it puts you or anyone else in danger or if you believe it may cause damage to your, or another person’s property.