Why is Hard Water Problematic for Humidifiers?

You might have heard people complaining about the impact that hard water has on things around their home and wondered why is hard water problematic for humidifiers and usage around the house.

Hard water contains minerals that can affect the quality of the water and often leave insoluble deposits in laundry equipment, boilers, or cookware.

Hard water is problematic because of the calcium and magnesium minerals it contains, which form residues in humidifiers. The minerals affect the heating element in humidifiers and can damage your humidifier.

If you use hard water in your humidifier, you might notice a white cast at the bottom of the humidifier over time. The white cast is usually comprised of minerals like calcium and magnesium that are found in hard water.

Since water is usually crystal clear, differentiating between hard and soft water can be difficult unless you assess the water quality in a laboratory or use other techniques of differentiating between hard and soft water.

Before using the water in your humidifier or cookware, you will not be able to see the minerals with your naked eyes unless you perform tests that isolate the minerals.

This article will help you understand why hard water is problematic for humidifiers, how to tell if the water in your home is hard water or how to test for water hardness at home, and approaches that you can use to prevent hard water damage in your home.

In this post, we will cover:

What is Hard Water?

The different types of water that exist vary based on the contents or the processing that the water has undergone.

Hard water basically means water that contains high levels of mineral ions (metallic ions) like calcium and magnesium minerals.

Other metals that can be found in hard water in small amounts include iron, zinc, manganese, and strontium. Calcium and magnesium are usually the main minerals found in high concentrations in hard water. These minerals affect the texture and chemical composition of the water.

Types of Hard Water

Generally, there are two types of hard water, temporary and permanent. Hard water can also be classified based on the level of minerals in the water.

If the levels of minerals are more than 7.0 g grains per gallon (gpg) then the water is considered hard water. If the gpg levels of mineral deposits are between 3.5 and 7 then the water is considered moderately hard and if the levels of mineral deposits are between 1.0 and 3.5 gpg then the water is considered slightly or mildly hard.

Temporary Water Hardness

Temporary hardness can be removed by boiling the water. This is why you will notice that a cooking pot, kettle, or boiler used for boiling water regularly will have mineral deposits on the side.

Temporary water hardness entails the presence of soluble bicarbonates of calcium and magnesium. As such, the deposits that will form in your humidifier or other equipment in your home if you are using hard water that is classified under temporary water hardness will comprise calcium carbonate and magnesium carbonate.

When the water is heated the soluble salts of magnesium carbonate are converted into magnesium hydroxide, which is insoluble.

Since magnesium hydroxide is insoluble, it will get precipitated and can be removed by sieving the water. After filtering the water and removing the precipitate, the water will be converted to soft water.

If you do not filter the water as in the case of using a humidifier. The water will evaporate during heating and the insoluble minerals will appear like a white cast inside the humidifier.

Permanent Water Hardness

Permanent water hardness entails the presence of soluble chlorides and sulfides of calcium and magnesium. As such, the soluble salts in the water will be in the form of magnesium chloride or magnesium sulfide and calcium chloride or calcium sulfide.

Permanent water hardness is differentiated from temporary through a boiling test. Boiling the water will not remove the sulfide and chloride salts present.

Permanent water hardness can be removed by alternative water treatment approaches such as the use of washing soda. The washing soda will react with the water to form insoluble carbonates, which can then be removed through filtration.

How to Tell If the Water in Your Home is Hard Water

You can easily test for the water hardness in your home. To check if the water in your home is hard consider the following tests:

Chalky White Residue or Mineral Deposits

Hard water usually forms mineral or insoluble deposits on boilers, aluminum-based cooking pots, or humidifiers. The formation of these insoluble deposits occurs during the water heating process.

As the heated water evaporates, the insoluble calcium and magnesium minerals found in hard water usually remain on the lower part of the boiler or humidifier.

The mineral deposits can solidify on the inner parts of the container if the boiler or cooing pot is not cleaned with a scouring pad regularly.

Soap Scum

The mineral deposits in hard water react with soap to form soap scum. Soap scum is the greyish-white insoluble substance (precipitate) that appears on the side of laundry equipment when cleaning something using hard water.

When using soap with hard water, the water will not lather but will form a greyish-white precipitate. If you wish to test for the water hardness in your home, simply lather some soap in the water and allow the water to settle for a few seconds. If you notice a greyish-white precipitate then the water is hard.

Scale Build-Up on Faucets

Calcium and magnesium mineral deposits can build up on your faucets over time if you are using hard water in your home.

If you notice some scale build-up on your faucets that appears chalky white and are difficult to remove, then the water around your area is hard water.

Low Water Pressure from Showers

The mineral deposits linked to hard water can lower the water pressure of your shower head. The minerals in hard water can accumulate inside the plumbing system in your home and the showerhead.

Over time, the mineral deposits that have accumulated in the plumbing system will clog the water pipes and the spray nozzles of your shower head and lower the water pressure.

Why is Hard Water Problematic for Humidifiers?

Mineral Scale Deposition

Hard water causes the deposition of minerals in equipment, which can affect the performance of water distribution channels, boilers, irrigation systems, humidifiers, and other equipment used to distribute or store water.

If you are using a portable warm mist humidifier, you might notice some chalky white residue in your humidifier over time. While the mineral deposits will not affect the performance of your portable humidifier, the inner parts of the humidifier will be discolored.

On the other hand, if you are using a whole-house humidifier, then the mineral deposits will affect your humidifier’s performance significantly. Whole-house humidifiers rely on water distribution channels that are usually put in place during the installation process.

If you are using a warm mist whole-house humidifier, the mineral deposits in the water will accumulate in the water pipes over time and affect the water pressure. Some of the water distribution channels can be blocked if you do not conduct routine maintenance.

Reduces Heating Efficacy

Hard water can reduce the heating efficacy of equipment and increase your energy expenditure. The minerals in the hard water can build up in the humidifier near the heating element and increase the heating cycle duration. As such, the water might take longer to heat because of the build-up.


Hard water is problematic for humidifiers because it can cause corrosion. This can be a serious problem, especially for whole-house humidifiers. Aside from calcium and magnesium, hard water can also contain iron and other minerals.

The continued deposition of these minerals in water distribution channels that supply water to a whole-house humidifier can cause progressive corrosion of water pipes. The longer the minerals build up in the water pipes the worse the damage to the humidifier system.

Dispersion of Minerals into the Air

If you are using a cool-mist humidifier, the minerals in the hard water will be dispersed in the air unless the humidifier has a filter. A cool-mist humidifier does not heat the water before releasing the mist into the air. As such, the minerals in the water will be released into the air along with the water.

With time, the minerals released into the air when using a cool-mist settle on surfaces and form “white dust.” The white dust can affect the performance of your electronics if it gets inside the electronics and accumulate there over time.

Solutions that You Can Consider

Routine Maintenance

Conducting routine maintenance can help you prevent hard water damage. Calcium and magnesium deposits build up over time. This means that if you are constantly removing any calcium and magnesium deposits in your humidifier, you will not have to worry about water hardness problems.

You could call a professional plumber to help you with the routine maintenance of a whole-house humidifier and the entire plumbing system in your home.

This will ensure that the humidifier and the entire plumbing system are protected from hard water damage, which could be costly if it leads to corrosion and leakage of pipes.


If you are using a cool-mist humidifier in your home then you are not likely to notice any mineral deposits in your humidifier as the minerals will be dispersed into the air. The best approach for dealing with hard water would be to buy a humidifier with a filter.

Most humidifiers have these filters. If the filter in your humidifier is clogged due to the accumulation of mineral deposits on the filter, you should consider changing the filter to improve the performance of your humidifier.

Reverse Osmosis

Investing in a reverse osmosis system will eliminate the need to clean your humidifier frequently or the need to replace your filter after every few months. Reverse osmosis is a water purification method that separates the ions in water using a semi-permeable membrane.

In reverse osmosis, the water is pushed using a lot of pressure through the semi-permeable membrane, which in turn removes a high percentage of the contaminants in the water.

The benefit of using reverse osmosis is that it will remove the mineral deposits along with other contaminants, which might be present in the water.

You should note that installing reverse osmosis in your home can be quite pricey, especially if you plan to install it in your entire home. It will also increase your electricity consumption and increase your utility bills.

Understanding the electricity consumption of your humidifier and the potential changes that you will experience when you install reserve osmosis is essential in making an informed decision regarding whether or not you should install reverse osmosis.

Related: Electricity Use in Humidifiers

Boiling Water

You could consider alternative water treatment solutions like boiling. Boiling is a cheap and affordable way of removing mineral deposits in your water, especially when the water has temporary hardness.

While boiling is a cheap and easy method to use, it can be tiring boiling water every time you need to use your humidifier. This can be more draining when you have a cool-mist humidifier because you will need to give the water some time to cool before using it in the humidifier.

Water Softener Tablets/ Demineralization Tablets

It is clear that hard water is problematic for humidifiers. Water softening tables offer you an immediate solution to your hard water problem by demineralizing the hard water.

These tablets are compact, versatile, and easy to use. Aside from using them in the water to plan to use for your humidifier, you can also use them for other purposes around your home.

The water softener tablets work through an ion-exchange mechanism. Water softens when the carbonate, sulfide, or chloride ions in hard water switch place with sodium ions.

Water softening tablets contain sodium or potassium ions. Since potassium and sodium are highly reactive when compared with calcium, magnesium, zinc, and iron, the sodium or potassium ions in the tablets will easily replace the calcium and magnesium ions.

There are water-softening tablets designed for humidifiers that ensure that no residue will remain at the bottom of your humidifier. Using water-softening tablets is the easiest way of dealing with hard water around your home.


Hard water is problematic for humidifiers because of the mineral deposits that can accumulate in the humidifier over time or the minerals that might be dispersed into the air along with the misted water.

The impact of hard water in humidifiers is more pronounced in whole-house humidifiers than in portable humidifiers because of the risk of corrosion of pipes over time, reduced water flow, and leaks that might be caused by corrosion.

Using water softening tablets, installing reverse osmosis, and boiling the water before use are some of the solutions that you can adopt in your home to soften your water.


Difference between Hard and Soft Water

The difference between hard and soft water is based on their mineral composition. Hard water contains a higher percentage of calcium and magnesium minerals while soft water contains a high level of sodium.

Soft water can also be defined as water that has been processed to rid it of dissolved elements such as metals like magnesium. Hard water forms insoluble deposits on boilers or laundry equipment because of the mineral deposits.

What Can I Put in My Humidifier to Help with Hard Water?

You can use water-softening tablets to convert the hard water to soft water. Water softening tablets or demineralization tablets are effective for converting hard water to soft water. There are water-softening tablets that have been designed for humidifiers.

How do I Keep Hard Water from Ruining My Humidifier?

The easiest way of avoiding hard water damage is using water softener tablets.

Aside from using water-softening tablets, you could also ensure that you empty the water reservoir of your humidifier after every use. This will ensure that the remaining water does not sit in the reservoir for long, as that can allow the progressive buildup of mineral deposits.

You should also keep your humidifier clean at all times and use undiluted white vinegar. When using undiluted white vinegar, allow the white vinegar to soak in the water reservoir where the mineral deposits have accumulated for a few minutes and then clean the water reservoir with mild soap and clean water.

What Happens if You Don’t Use Distilled Water in a Humidifier?

You do not necessarily have to use distilled water in your humidifier as this might be an additional cost to you and your household. If you do not want to use distilled water in your humidifier, you could use water-softening tablets to soften your tap water. This can be particularly beneficial if you live in an area with hard water.

Does it Matter What Kind of Water You Put in a Humidifier?

In most cases, it does not matter what type of water you use in your humidifier especially if you are using a cool-mist humidifier. The cool-mist humidifier will dispense the water placed in the humidifier regardless of the type of water your use.

However, it is important to ensure that the water placed in your humidifier is clean. Using dirty water in your humidifier can be a potential health hazard because of the increased risk of respiratory diseases.

Some humidifiers have been designed to filter out mineral deposits found in hard water along with bacteria and dirt particles found in tap water.

Understanding the type of humidifier that you have is important as it will help you determine whether you need to invest in additional water purification methods.

Why Should You Not Use Tap Water in a Humidifier?

Tap water can contain high levels of contaminants and minerals like calcium and magnesium, which contribute to water hardness. The mineral deposits can accumulate in your humidifier over time and affect the performance of your humidifier.

Aside from that, these mineral deposits also promote microbial growth, which means that you might start noticing the growth of mold in your humidifier if you do not empty your humidifier regularly.

If you clean your humidifier regularly and it has a filter to remove the mineral deposits, you could still use tap water. Note that the minerals in hard water can clog your humidifier’s filter with time, which will require you to replace the filter.

Is It Okay to Use Hard Water in a Humidifier?

Hard water affects the heating elements of warm mist humidifiers. The minerals in hard water will accumulate near the heating elements and create a chalky white deposit. The mineral deposit can also affect your humidifier’s ability to heat water properly and convert it to warm mist over time.