Can I Use Deionised Water in my Steam Iron?

by Lucy Bell-Young

You might think that using deionised water, or indeed any form of purified water in your steam iron would do nothing but good. However, purer does not always mean better, and steam iron manufacturers often caution consumers against using deionised water in this appliance.

The Household Myth

The reason most people believe that deionised water is the way to go when it comes to steam irons is because of two main factors:

  1. Lime-scale build-up caused by mineral deposits
  2. The lack of minerals present in purified water

Since deionised water has undergone deionisation, it doesn’t contain mineral salts like calcium, which can cause lime-scale in a variety of appliances like steam irons, kettles and even shower heads. When lime-scale accumulates, it can dramatically affect the efficiency and longevity of the appliance.

The type of water that is most likely to cause this build-up of minerals also happens to be the most readily available water in the UK – tap water. This forms the basis of the myth that only deionised water should be used in steam irons.

A white steam iron on an ironing board


Hard Water

In general, there are 2 types of tap water in the UK:

  • Soft Water contains a very low concentration of minerals, especially calcium and magnesium. This is because it is naturally found near impervious, calcium-deficient rocks
  • Hard Water contains a very high concentration of minerals because it is formed when water filters through deposits of limestone and chalk. These contain very high amounts of calcium and magnesium carbonates and infuses the water with them

While different regions of the UK have varying degrees of these water categories, approximately 60% of the country has hard water. It is no wonder, then, why using tap water in steam irons has got such a bad reputation. Because of its high mineral content, hard water deposits calcium carbonate onto a given surface once it has evaporated. These deposits quickly accumulate to form lime-scale.

The logical solution to this problem is using water that not only a lower concentration of minerals but actually has no mineral content at all. Deionised water fits this profile, but is it doing more harm than good?

Using Deionised Water in Your Steam Iron

Deionisation is a purification method that involves passing raw water through ion exchange beds. During this process, all of the charged ions present in the water are replaced with hydrogen and hydroxide ions. These then combine to form pure H2O that contains no charged ions.

The success of this method can be checked by running an electric current through the water. If the solution is not conductive, then deionisation has been successful.

With no minerals, deionised water is very unlikely to cause any mineral build-up. In fact, this is why it is used to clean laboratory instruments, mechanical parts and even electric circuit boards. But this is not the reason why it isn’t recommended for steam irons.

Deionisation anion regeneration tank

The Problem of Using Deionised Water in a Steam Iron

The first issue with using deionised water or any form of purified water in your steam iron is that they can often cause it to spit and leak. Spitting happens when the steam vents in your iron are partially clogged with mineral build-up, causing the steam to shoot out in unpredictable spurts. However, it isn’t only the accumulation of minerals that can cause blockages to your steam vents.

When any form of purified water comes into contact with air, it quickly absorbs and dissolves carbon dioxide. When this happens, a weakly acidic solution of carbonic acid is formed. This has the capability of corroding metal over time and is only one of the reasons why demineralised water can actually eat through steel.

If the deionised water you use in your steam iron contains dissolved carbon dioxide, it will slowly corrode the metal parts of the iron and this could not only affect its longevity, it could also cause build-up in the steam vents. Therefore, whether you only use tap water or only use deionised water, you may still be faced with the same problem.

So what is the solution?

The Best Water for Steam Irons

First and foremost, it is always important to check the manufacturer’s guide on your steam iron because different models may require different types of water. For example, a steam iron that includes a calcium-cleaning system will perform perfectly well with hard tap water.

If you don’t have access to your manufacturer’s guide, the general rule of thumb is to use a 50/50 split between regular tap water and some form of filtered, or purified water. This way, you get the best of both worlds and minimise any risk of lime-scale or overall build-up.

Even if you don’t have access to filtered or purified water, tap water is completely fine to use as long as you take care of your steam iron and clean it properly. But using deionised water on its own could cause more problems than using tap water on its own, so always do your research first.

A green steam iron flat-side down on creased white fabric

For comprehensive information about deionised water, check out our Complete Guide to Deionised Water resource.

ReAgent sells high-purity deionised water in its online shop. This product is not only back by a 100% quality guarantee, but it is also available in a huge range of pack sizes in order to meet your specific business needs. Order online today or contact one of our friendly experts for more information.


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