How to prevent limescale in boilers

In order to get rid of limescale, you need to understand what causes it. Limescale is a white substance that can build up around appliances that use water. This means that your taps, washing machine, dishwasher, toilet and shower can all be affected by this chalky element. Limescale is a build up of calcium carbonate that is present in hard water. Limescale will build up faster on hot water appliances. This is because hot water evaporates off a surface much quicker than cold water would.

If you live in a soft water area, you won’t have an issue with limescale, however you may find that your taps start to erode over time. This is because soft water is more acidic. Unlike soft water, hard water contains additional minerals such as calcium and magnesium. When water evaporates off a surface, it leaves these mineral deposits behind and this is what causes limescale. When limescale accumulates in your central heating pipes, it can cause a blockage that will restrict the flow of water.

If you know that you live in a hard water area, you may potentially have a limescale problem in your heating system. But how do you know if you have a limescale issue when you can’t see it?

You might have noticed that your boiler is noisier than usual. This noise can be caused by water that becomes trapped where the limescale has built up. This water overheats and begins to evaporate, creating bubbles and steam. This is known as ‘kettling’. Kettling puts extra strain on the boiler and forces the system to work harder. Blockages caused by limescale will also make your boiler overexert itself. This means that both kettling and blockages can make your boiler less efficient and shorten its lifespan.

British Water has said that limescale could reduce your boiler’s efficiency by up to 12 per cent. This is because the boiler has to work harder to maintain the heat level you’ve set on your thermostat.

Fernox, a manufacturer of water treatment products, claims that just 1/16 of an inch of limescale around a copper pipe could increase your fuel costs by up to 15 per cent. Limescale isn’t just bad for your system, but for your purse strings too. 

A power flush is a mix of chemicals and water that is put through your heating system at high pressure. A pump will be connected to your central heating system and will push the chemicals through the pipes, boiler and radiators. As the solution moves through the pipes, any limescale deposits will break away and get flushed out. A power flush doesn’t just remove limescale; it will also expel any rust or debris in the system, which could also make your boiler more efficient. 

You may need to have your system flushed if your home experiences any of the following:

• Cold spots in your radiators
• Cloudy tap water
• Leaking or noisy radiators
• Excessive noise coming from the boiler
• Discoloured water that appears when you bleed a radiator
• Radiators taking a long time to warm up

A power flush will take around half a day to complete, but it may take longer if you have an open vent heating system.

Once you’ve removed limescale using the power flush method, you will want to put some preventative measures in place to stop it from coming back. You might consider the following options:

• Water softeners
• Scale reducers

A water softener removes minerals from the water that cause limescale. As the water comes into your home via the mains supply, it can be directed through a tank where a process known as ‘ion exchange’ takes place. Calcium, magnesium, iron and sodium are all positively charged and are the main elements that cause limescale. When the water goes through the softener tank, these minerals pass through negatively charged resin beads. The beads work like a magnet and hold on to the positively charged elements. The newly created soft water is then supplied to the taps and pipes in your home.

There are two types of scale reducer that you can purchase. A magnetic scale reducer works like a water softener and collects the minerals that cause limescale before they enter your system. Electrolytic scale reducers work by altering the structure of the limescale so that it cannot stick to the inside of your pipes. Both of these scale reducers can be added to your boiler by a suitably qualified engineer.

As we’ve previously mentioned, soft water is more acidic. In contrast, hard water is more alkaline, and with hard water comes problems with limescale. Therefore, you may want to try and reduce the alkalinity of your boiler water, making it slightly softer and reducing your limescale issues. Scale reducers are one way to do this, as described above, but water softeners are the best option.

A water softener reduces the hardness of water by removing the minerals from the water that cause limescale, including magnesium and calcium. As the water comes into your home via the mains supply, it can be directed through a tank where a process known as ‘ion exchange’ takes place. Calcium, magnesium, iron and sodium are all positively charged and are the main elements that cause limescale. When the water goes through the softener tank, these minerals pass through negatively charged resin beads. The beads work like a magnet and hold on to the positively charged elements. The newly created soft water is then supplied to the taps and pipes in your home.

Without the added minerals, the alkalinity of the water should reduce enough to keep your central heating system free of blockages and debris. 

While limescale can be annoying when it clogs up your heating system and makes it less efficient, it isn’t bad for you, so don’t worry if your taps and kettle contain the chalky element too. On the contrary, hard water contains minerals that are good for your body, although some people do claim that it can make your skin dry. If the thought of drinking it bothers you, you can always switch to bottled water, but limescale doesn’t have a negative impact on your health. Your boiler, dishwasher and showerhead might say otherwise.