How to descale a boiler like a professional (UK Guide)

When we think of limescale, we automatically think of kettles, showers, and bathtubs; however, this mineral deposit is also the silent slayer of boilers.

You probably think this is a rather dramatic statement; however, limescale significantly affects boilers in two ways.

First, it shortens the boiler’s lifespan, and second, it affects the boiler’s energy efficiency resulting in higher energy bills and less heat!

Thankfully there are ways we can get rid of and limit this pesky mineral build-up in our central heating systems. Firstly, by descaling regularly and secondly by ensuring a proper maintenance plan is followed.

First, we will look at how limescale builds up in your heating system and the damage it causes.

Then we will move on to descaling your boiler and how you can eliminate this irritating mineral deposit and thus save your boiler from an early demise!

Limescale vs. boilers

If you live in an area that is prone to hard water, chances are your boiler is busy accumulating limescale as we speak!

Unfortunately, every time the boiler heats the water, minerals such as magnesium and calcium, naturally found in hard water, form deposits.

These deposits become thicker over time and usually form in the central heating system, pipes, and radiator system. Because of limescale’s sticky tendencies, it literally sticks to everything.

As a result, it causes deposit build-up on the inner parts of your heating system. This puts pressure on the boiler as it struggles to push the water around the clogged pipes and radiator system.

As a result, the more pressure the boiler is under, the higher the energy and heating bills become.

Signs limescale is taking over

  • Reduced water flow.
  • Cold radiators.
  • Noisy boiler.
  • Boiler breakdown.
  • Clogged pipes.
  • Insufficient heat.
  • Cold spots on radiators (radiator sludge).

If any of these signs describe your central heating system, it’s probably an indication of limescale build-up.

While easy to ignore in its initial stages, if left, it can cause the eventual breakdown of your boiler and, subsequently, costly repairs.

When should you descale your boiler?

Descaling your boiler should not only occur when the obvious signs of limescale make their presence known.

In fact, descaling should be part of your regular maintenance routine to prevent limescale rather than treat it.

This is especially true for sealed systems such as the combi boiler. These systems are particularly vulnerable to limescale build-up.

This is because hot water creates more limescale than cold water due to its high evaporation rate.

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How to descale your boiler

Firstly, if you are unsure of how to descale your boiler and feel it’s a job best left to the professionals, check your warranty and see if descaling is included in your boiler package.

However, for those with some DIY knowledge, it’s possible to descale your boiler using limescale remover specially made for central heating systems.

Descale your boiler using these easy steps

Follow the steps below to descale your boiler and protect it from unnecessary repairs:

  1. Turn off the boiler.
  2.  Allow the central heating system to cool.
  3.  Switch off the water to the property using the outside shut-off valve.
  4.  Open the inside taps and drain all the water from the system.

Now that the system is drained, we can start the descaling process, which is slightly different depending on whether your system has a water tank or not.

Water tank

  • Check the label on the limescale removing product you are using and add the recommended amount to the cold-water tank.
  • Fill the tank with cold water until the feed connection is covered
  • Turn the water back on using the outside shut-off valve
  • Next, turn on the boiler
  • Allow the system to heat up over the next four hours while the descaling process completes.
  • Turn on the hot taps every twenty minutes, flushing hot water through the system during the four hours.
  • Lastly, flush the system using cold water, draining it 3-5 times. This will complete the cleaning process and reset the system.

Combi boilers

This type of boiler does not have a water tank and will require the descaling of the heat exchanger instead.

Unfortunately, removing the heat exchanger to descale it properly can be pretty tricky, and you may need the assistance of a heating engineer.

If you are unsure how to remove the heat exchanger rather seek professional advice as unnecessary repairs are both frustrating and costly!

How to protect your boiler from limescale

While descaling your boiler regularly is an excellent maintenance plan, prevention of limescale is better.

Living in a hard water area means your boiler is exposed to a lot of limescale build-up.

However, you can take steps to ensure limescale deposits are kept at a manageable level between each descaling.

  • Power-flush

A power flush should only be done by a professional heating engineer and can be incorporated into your boiler’s annual service.

This process uses chemicals and water mixed to form a sludge-dissolving mixture. The mixture is then pushed through the heating system at high pressure, forcing the limescale and dirt out of the system.

  • Water softener

This handy device can be installed into the central heating system to prevent limescale from developing.

How does it work? Using ions and science-based technology changes the water’s composition. i.e., softens the water by positively charging the main elements found in limescale.

  • Scale reducer

This magnetic device can be used in conjunction with a water softener to prevent the build-up of limescale.

It actively attracts the minerals found in hard water that cause the development of limescale.

In addition, it prevents limescale from sticking to the inside of radiator pipes and inhibits the production of sludge build-up.

Related reading: 

Final word

By limiting the build-up of limescale within the central heating system, you can prolong the lifespan of your boiler. In addition, an efficiently functioning boiler will ensure your energy bills remain within budget.

And while descaling, power-flushing, and additional softeners or reducers may seem tedious to maintain, it will save on costly repairs in the long run.

So, the next time you turn on the heating, take a moment to consider when last your boiler had a decent descaling!

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