What Does The Water Softener Hardness Number Mean?

The water softener’s hardness number is a measure of the hardness of the water entering the water softener.

The higher the number, the harder the water.

There are many factors affecting the water hardness number and what level best suits each household’s needs for daily water use.

But first, we must define the term “hardness” as it applies to water quality. Hardness is a measure of calcium carbonate (CaCO₃) concentration in your water supply.

Other materials, such as magnesium and iron salts can also contribute hardness of your water, but not as much as CaCO₃.

Two Types of Water Hardness:

Temporary hardness.

It refers to dissolved bicarbonates that convert into carbonates when heated (i.e., boiled).

Permanent hardness.

This occurs when minerals in your water have crystallized, or precipitated out, and become solid particles suspended in the water.

The water hardness of your water supply is important because it affects the performance of soaps and detergents. Soap scum forms when soap reacts with hard water minerals to create a sticky, insoluble film.

This can leave fabrics feeling stiff and rough, make glasses cloudy and difficult to clean, and form scale on fixtures and inside pipes over time.

Water hardness scale is a build-up of solid material that can clog plumbing systems, reduce flow rates, and increase energy costs due to increased heating requirements.

It is therefore important to choose an ideal water hardness level for your needs in order to minimize these problems.

A good rule of thumb is that if your area has a hardness level greater than 120 mg/L as calcium carbonate (CaCO₃), you should consider installing a water softener.

You can find out the hardness level of your water area by contacting your local water utility company.

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Factors Affecting Water Hardness


The temperature of your water affects how much temporary hardness it contains.

Warm water usage from hot water heaters dissolves more bicarbonates (a type of temporary hardness) than cold water. This is why hot showers can leave your dry skin itchy.

The high temperature of the water causes more bicarbonates to dissolve, leaving you with less soap scum-fighting power!


The pH of your water also affects hardness. Water that is more acidic (has a lower pH value), will have more temporary hardness than alkaline (higher pH) water.

This is because carbonates are less soluble in acids than in alkaline.

So if you have very hard water and you’re looking for ways to reduce the amount of scale build-up, try lowering the pH of your water,  using an acidifier like phosphoric or nitric acid.

Mineral content

The mineral content of your water will affect its temporary and permanent hardness.

For example, if there are more bicarbonates dissolved in the water than carbonates (as is often seen with groundwater sources), then this indicates a higher level of temporary hardness.


Water treatment plants use chemicals like calcium hydroxide to add additional minerals into the supply, which increases TDS levels.

It also decreases in acidity; however, they do not remove hardness.

If you have a basic water softener, it will remove some of the hard minerals from your water supply.

However, if it is not properly maintained, it can actually add more hardness minerals back into your water!

Now that we’ve looked at some of the factors affecting hardness, let’s take a look at what levels might be best for different types of households.

Hardness Levels  For Different Types of Households:

120-159 mg/L as calcium carbonate (CaCO₃)

This range is generally considered to be moderate hardness and is suitable for most households.

It can cause problems like soap scum and scale build-up, if not treated, but is manageable with regular maintenance.

160-199 mg/L as CaCO₃

This is considered to be hard water and may cause more problems like scale build-up, corrosion, and staining.

It is generally recommended that a water softener be installed if the hardness level is above 160 mg/L.

200 mg/L or greater as CaCO₃

This is very hard water and can cause significant problems like extensive scale build-up, metal corrosion, and staining.


What level should I choose for my home?

The amount of hardness level that’s best suited for your household will depend on a number of factors.

This includes how much water you use daily, what type of appliances or fixtures are being used, and whether any members of your household have skin allergies or other sensitivities to hot water.

You might need to do some experimentation in order to find what setting works best for you.

However, as a general rule-of-thumb, softening between 15-20 grain capacity per gallon of water (GPG) should suffice most people’s needs.

How does softening water affect the environment?

Softened water has less calcium carbonate in it than hard water, which means that fewer minerals are being deposited onto surfaces where they could form scale buildup or get into waterways.

This could potentially harm aquatic life over time when dissolved oxygen levels drop too low due to excessive scaling up of pipes.

What factors affect the hardness setting on your water softener?

A:  Your water softener’s hardness setting is determined by three factors: the ppm of iron, the grains of hardness, and age.


A water softener should definitely be considered if the hardness level is this high.

If you have a high-efficiency (high-end) water softener, you may need to find the location of your “master” control valve to ensure it is set correctly.

This will help to avoid overcharging the water softener tank and power outage. The water softener hardness setting number is used to measure the hardness of the water.

The higher the hardness level, the more hard mineral build-up is present in the water.

It is important to remember that the water softener only removes excess hard minerals.

The softening process does not remove completely dissolved minerals like calcium and magnesium from the water supply.

The level of hardness in your home depends on where you live, the number of people in the household, and the amount of water, or maybe you have an older water softener installed.

So if you’re worried about what level of hardness might be best for your home, try using an inexpensive test strip kit and wait for the test result.

Test first before making any major changes just so there aren’t any surprises along the way.

Most people have water softeners installed with a brine tank that holds much salt and iron content.

Mineral tanks are the heart of a water softener. They are filled with small resin beads, placed on the resin beds.

To enjoy the full benefits of a soft water system without absorbing these costs, convert your softener to use potassium chloride to help on your water conditioner.

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D. Hahn

DIY guru, dad, husband, blogger. When I'm not creating life hacks I'm teaching my kids how to fix stuff after their dad breaks it.

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