How to Prevent Limescale in Boilers

Limescale build up on heating element

You’ve seen limescale in your kettle and probably scraped some of it off your bathroom taps, but most of us don’t consider the formation of limescale in our boilers and central heating system. As with any appliance that sees lots of water flow through it, limescale can build up quickly in boilers and can inhibit its performance. It’s likely that your boiler is imperative to the function of your home, however, and so preventing limescale build-up is very important.

Limescale is a white/grey chalk-like substance that is a build-up of calcium carbonate. Hard water contains more minerals than soft, and so limescale is more prevalent in hard water areas than soft. When water evaporates off of a surface, the mineral build-up is left behind – and this is limescale. When limescale accumulates in central heating pipes, it blocks the hot water circulating as it should, and so limits the performance of radiators or other heaters linked to them. It’s estimated that a 1mm build-up of limescale can affect radiator performance by up to 7%.

If your boiler is more noisy than usual, or your overall heating performance seems to have decreased, then it may be due to limescale in the system. However, unlike your kettle, you probably don’t have much access to the inside of your boiler, and so the cleaning and prevention methods that are mainstream for limescale won’t work in the same way. Read on for information on how to prevent limescale in boilers as part of routine radiator boiler maintenance – without the need for professional intervention.

If your boiler already has limescale build-up and it needs removing, seek professional advice. Taking steps to prevent limescale in your boiler can be done thereafter.

Step-by-step guide

If you live in a new-build home in a hard water area, UK Building Regulations state that you must have some form of limescale inhibitor installed – so you shouldn’t need to take any further action. If you’re unsure as to whether that’s the case, contact your estate agent or construction firm for further info.

  • If you live in a hard water area, speak to your local heating engineer and/or the manufacturer of your boiler. Ask them for their recommended type of limescale prevention system for your appliance
  • If purchasing a water conditioner, follow the instructions on the packet to introduce this into your water system. A water conditioner will change the composition of the water and prevent mineral deposits from building up and sticking
  • If purchasing an electronic conditioner, contact a professional boiler engineer and have them install it. Electronic conditioners are powered by your mains supply and will soften the water in your pipes gradually
  • If purchasing a limescale filter for a combi boiler, you’ll likely be buying a magnetic filter that collects rusted debris from the inside of pipes and tanks. These must be installed by a professional only
  • If you have been advised by a specialist that you’re able to treat your boiler water yourself, purchase purpose-specific phosphate crystals and hang these in a well secured bag in the water tank. Follow manufacturer’s direct instructions for this and ensure the bag is not at risk of coming loose. Phosphate crystals in water prevent the formation of limescale, but may need replacing regularly.

How often should you service your boiler?

It’s all too easy to forget about your boiler until something goes wrong with it; but by then, it may be too late! So how often should you service your boiler? Well, in truth, you shouldn’t – unless you’re a qualified and registered boiler engineer. You should have a specialist visit your home to service your boiler once every 12 months; and if you’re a landlord or managing a commercial property, this will be a legal requirement.

A boiler service can take just 10 minutes and is usually fairly inexpensive, but can extend the lifespan of your boiler by a vast period (we’re talking years!) and prevent any limescale build-up or other issues from happening at all. Most boilers come with a five-year warranty, and some, a ten, but however long the warranty is, it must be regularly serviced for this to stay valid. At the end of each service, the engineer will supply you with a paper maintenance certificate. Keep this somewhere safe – it’s your proof of ongoing routine boiler maintenance.

If you have any questions about central heating systems or need advice on radiators and pipework no matter how hard the water in your area is, get in touch. Here at Great Rads we love to chat all things heating and radiators.


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