• 1. Our advice is clear:
    • The first and best thing you can do to minimise the risk that your gas appliances produce CO is to ensure that they are safety checked annually by a suitably competent and qualified Gas Safe registered engineer. If your boiler plan covers an annual service and you haven’t had one yet in this plan year you can find the contact number to arrange this in 'myaccount'
    • An audible CO alarm will activate in the presence of CO. It’s a good second line of defence, but can only tell you when something has already gone wrong
    • Make sure any alarm you buy is marked to EN 50291 and has the British Standards Kitemark
  • 2. Carbon monoxide alarm — A good second line of defence

    Modern CO alarms are similar in design to smoke alarms (which do not detect CO) and can be purchased from around £15 at many major retail outlets including DIY stores and supermarkets. We do not recommend the use of 'black spot detector' warning strips — they are too easy to miss and won't alert you if you have a CO leak when you're asleep.

    It’s advisable to fit an alarm in every room with a gas appliance, and when installing and siting the alarm make sure you refer to the manufacturer’s instructions. Typically, audible CO alarms have a battery life of up to 5 years. If you’re unsure which alarm to get, you can ask a Gas Safe registered engineer for advice.
  • 3. 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.