How to Descale a Kettle

Why do kettles become ‘scaly’?

If you only ever fill your kettle with water from the tap, then you may be wondering why your kettle has suddenly developed a build up of limescale at the bottom…

The answer lies in the water itself. 

Limescale is a natural substance that is made up of various compounds, but primarily calcium bicarbonate and magnesium bicarbonate. 

These compounds make their way into the water when rainwater filters through ground rocks before reaching the water table underground. The water effectively ‘leeches’ these compounds from the rocks. This results in water rich in compounds that can result in the build up of limescale. This compound rich water is known as hard water.

Because of the role that geology plays in creating mineral-rich water, you’ll typically find that limescale only occurs in kettles in certain parts of the UK. 

Therefore, if you live in an area where rainwater filters through chalk and/or limestone rock formations, you’ll end up with hard water coming out of your taps. Parts of the UK that are particularly prone to hard water include: 

• The South East - areas that draw their tap water from aquifers near formations like the Lewes Nodular Chalk Formation (much of the South East outside of London), or Seaford Chalk Formation (Salisbury and the surrounding area) are prone to hard water. 
• Yorkshire - areas that draw their water from aquifers near formations like the Monsal Dale Limestone Formation are prone to hard water. 

Note - it’s important to note that even if you live in an area that is traditionally known for hard water, you may not always get this from your taps. In some cases, the water source will change during different times of year, coming variously from local aquifers or distant reservoirs. A relevant example is Birmingham, which actually draws the majority of its water from Wales (which is a soft-to-medium water area). 

So, if you live in an area that does have hard water, you can expect your kettle to experience a build up of limescale from time-to-time. 

But, if you’re of a particularly curious bent (like ourselves here at Morphy Richards), you may want to know exactly how limescale forms inside your kettle. 

Well, let’s take a look…

The underlying cause for limescale build up in kettles is the way in which the water, the minerals dissolved within the water, and the repeating heating cycles all interact. 

The process of limescale build up, goes a little something like this: 

• You add water from the tap to your kettle. 
• You hit the switch on your kettle to begin the boiling cycle.
• As the heating element does its work, the water in your kettle boils. 
• Water (at sea level), has a boiling point of 100ºC.
• However, minerals such as calcium bicarbonate and magnesium bicarbonate have much higher boiling points (around 333.6ºC). 
• As a result, over repeated boiling cycles, calcium bicarbonate and magnesium bicarbonate will be ‘left behind’ by the boiling water, accumulating and forming limescale. 

And, that is how limescale forms in your kettle! It’s all down to a bit of science…

A note on temporary and permanent water hardness

Did you know that there are actually such things as temporary hard water and permanent hard water? 

The former (temporary hard water), is water which contains bicarbonate minerals (e.g. calcium bicarbonate and magnesium bicarbonate). These compounds are easily removed from water through the act of boiling - but, that does result in build-ups of that pesky limescale. 

On the other hand, there is such a thing as permanently hard water. This is water that contains the sulphate forms of magnesium and calcium. These compounds can only be removed from the water using an ion exchange process. 

For the purpose of your kettle, this doesn’t really matter - but, it’s nice to know!

How ‘hard’ is hard water?

So, hard water contains calcium bicarbonate and magnesium bicarbonate. That’s all very well, but how much of these compounds does water have to contain before it’s classed as ‘hard’?

Handily, the Drinking Water Inspectorate (yes, there is such an organisation!), has set out the levels at which water becomes ‘hard’ - based on calcium carbonate. 

These levels are as follows: 

Tip - the Drinking Water Inspectorate has published a handy map of the UK, which sets out hard water concentration by area.

How can you tell if you have hard water at home?

With all this talk of limescale build up - and the prospect of your lovely kettle becoming ‘scaly’, you might be keen to find out if you have hard water coming out of your taps at home.

Luckily, it’s fairly easy to find out. 

Signs that you have hard water

There are a number of incidental signs that you can look for which indicate you have hard water at home. These signs to look for include: 

• The bottom of your shower or the rim of your bath regularly becomes scummy.
• A build up of white crusts (or deposits) around taps, shower heads and drains. 
• Washing up involves plenty of filmy, hard to clean dishes. 
• And - of course - a build-up of limescale in your kettle!

If you regularly spot these things around your home, then it’s likely you have hard water coming out of your taps. 

However, if you want more certainty regarding your water condition, then there are some simple tests you can do. 

How to test for hard water

Got an empty bottle spare? Do you have some liquid soap to hand? Then you’ve got everything you need to test for hard water. 

Start by unscrewing the cap from your empty bottle and filling it about one-third full with cold water from the tap. Next, add a few drops of liquid soap to the bottle. Screw the cap back on the bottle, and then give the whole thing a few vigorous shakes. 

If, once the water has settled, there is a distinct lack of fluffy bubbles (a.k.a. ‘suds’) atop the water - and the water appears milky or cloudy - then you’ve almost certainly got hard water. 

Note - this test isn’t always accurate as many liquid soaps are formulated with detergent and thus will lather up and create suds in both hard and soft water. If you really want to do this test, then use a basic ‘base’ soap. 

Should you want to take a more ‘scientific’ approach, then it’s actually possible to buy water hardness testing kits from hardware and DIY stores. These typically cost only a few pounds. 

How to descale a kettle

So, with all that in mind, it’s time to get to the crux of this article - what’s the best way to descale your kettle? 

The answer to this question depends on whether you’re happy to use an artificial descaling product, or you’d rather use an all-natural formulation. 

To begin with, we’ll take you through the process of descaling a kettle using an artificial descaling product.  

How to use a kettle descaler

Kettle descaler products are widely available, and can typically be picked up in your local supermarket. Whilst each individual product will have specific usage instructions, we’ve outlined some general steps you can follow below: 

Prepare your descaling solution

Most descaling products will require you to prepare a solution before adding it to your kettle. This normally involves mixing a certain volume of the product with a specific amount of water. 

Once prepared, the solution can then be poured into your kettle. 

Boil your kettle

The majority of descaling products will require you to bring the kettle to boil once the solution has been poured in. 

Note - it’s important that you allow the kettle to complete a full boiling cycle. Don’t be tempted to turn it off early like you would when making a cuppa!

Allow the descaling solution to sit

Once the kettle has completed its boiling cycle, allow the (now boiling) descaling solution to sit in the kettle for a minimum of 20 to 30 minutes. This will allow the solution time to really ‘get to work’ and break down the limescale build up. 

Descaler products tend to be formulated using mildly acidic agents - which react with compounds such as calcium bicarbonate and magnesium bicarbonate, breaking them down.

Unplug and rinse thoroughly

Once that minute hand has ticked past the 30-minute mark, it’s time to unplug your kettle, pour the descaling solution down the kitchen sink and give the inside of your kettle a thorough rinse with fresh, cold water. 

Tip - once you’ve given your kettle a rinse, be sure to inspect the inside. If your kettle had a particularly bad build up of limescale, you may need to treat it with the descaling solution a second time.

Boil the kettle (again)

Once you’re satisfied that your kettle is free of limescale, give it another final rinse before filling it with fresh water and bringing it to the boil again. This will ensure that the kettle is completely clean and residue free before you next use it. 

How to descale a kettle with natural ingredients

If, for whatever reason, you decide not to use a descaling product, then it’s entirely possible to remove limescale using all-natural methods. 

There are three widely recognised ways to naturally remove limescale from a kettle; using baking soda, using lemon juice, or using white vinegar. Below, we’ll take you through each one. 

Baking soda

Long a ‘household essential’, baking soda has found myriad uses in the home throughout the years. So, it’s probably no surprise to learn that baking soda is pretty good at descaling kettles. 

Here’s how to use it: 

• Unplug your kettle. 
• Mix a tablespoon of baking soda with a very small amount of water. Mix together until you have a thick, granular paste. 
• Rub and spread this paste over any internals that have a build up of limescale (e.g. the heating element). 
• Use an old toothpaste to rub and agitate the baking soda paste into the limescale. 
• Allow the paste to sit for 5 to 10 minutes.
• Rinse away the baking soda paste with cold, fresh water. 
• Inspect the inside of the kettle to ensure the limescale has been eradicated.
• Allow the kettle to dry before filling it up with fresh water and plugging it back in.

Lemon juice

Another household favourite is lemon juice - which can be used in several home cleaning applications. Here’s how to use lemon juice to descale a kettle: 

• Fill your kettle with water, ensuring it is plugged in. 
• Squeeze the juice of two lemons into a small cup or jug (make sure no pips or flesh end up in the juice!). 
• Pour the lemon juice into the kettle. 
• Boil your kettle. 
• Allow the water/lemon juice to sit in the kettle between 20 and 30 minutes.
• Unplug the kettle and pour the water/lemon solution down the kitchen sink.
• Rinse the inside of the kettle thoroughly with fresh, cold water. 
• Leave to dry before refilling with fresh water and plugging the kettle back in.

White vinegar

Another popular all-natural cleaning option is white vinegar - its mild acidity giving it the power to break down all kinds of unpleasant build-ups - including limescale. Here’s how to use white vinegar to descale a kettle: 

• Fill your kettle with half fresh water, and half white vinegar. 
• Bring your kettle to the boil. 
• Allowing the water/white vinegar solution to sit and rest for between 20 and 30 minutes. This will allow the acidity of the vinegar to work upon the limescale. 
• Unplug the kettle and empty the solution down your kitchen sink. 
• Rinse out the inside of the kettle thoroughly with fresh water. 
• Inspect the inside of the kettle to ensure the limescale has been eliminated. 
• Leave the kettle to dry before refiling with fresh water and plugging back in. 

As you can see, whether you want to go down the artificial or all-natural route, there are plenty of easy, convenient ways to descale your kettle.