At What Hardness Is a Water Softener Needed?

Updated on:
January 5, 2024

If you’ve noticed soap scum spots on your dishes, shower tiles, and glass surfaces, or your hair has felt drab and your clothes not quite clean, your water is probably full of hard minerals like calcium and magnesium. 

But fear not — that’s where a water softener comes to the rescue. It’s like a superhero for your home’s water quality, swooping in to swap out those pesky minerals for something gentler, making your water kinder to your skin, appliances, and sanity. 

Of course, if your water is only a bit hard and not very hard, a water softener might not be the answer. In this article, I’ll talk about how hard your water needs to be before you invest in a water softener.

At What Hardness Level Do You Need a Water Softener?

Here’s a water hardness chart that provides the classification of water hardness based on grains per gallon (GPG), parts per million (PPM or mg/L), and the corresponding hardness level from soft to extremely hard, with approximate values:

GPG (grains per gallon)PPM (parts per million or mg/L)Hardness classification
1–317–51Slightly hard
3–751–120Moderately hard
10+180+Very hard
10–20180–340Extremely hard

The need for a water softener in a household typically arises when the water hardness level exceeds a certain threshold that negatively impacts daily activities and appliances. 

At a “very hard” level, the effects of hard water become even more noticeable in a variety of ways:

  • Soap and detergent effectiveness decreases, resulting in difficulty lathering and increased soap consumption. 
  • Scale buildup becomes a concern in appliances like hot water heaters, dishwashers, and washing machines, reducing their efficiency, lifespan, and potentially leading to higher energy bills. 
  • Plumbing systems may suffer from mineral deposits, causing reduced water flow and potential clogs. 
  • The aesthetic experience of using hard water can be less pleasant, as it may leave soap scum, spots, and residue on dishes, fixtures, and glass surfaces.
  • Clothing washed in the hard water seems to never get fully clean as a result of poor detergent performance.
  • Skin condition can deteriorate, especially among those with eczema or acne problems.
  • Hair may show visible signs of weakness, dullness, or stunted growth.
  • Odd, metallic, or chemical taste in drinking water. 

To alleviate these issues, homeowners often opt for a water softener. This device exchanges calcium and magnesium ions responsible for water hardness with sodium ions through a process called ion exchange.

By doing so, the water softener effectively reduces the hardness of the water, leading to improved cleaning, extended appliance lifespans, and enhanced overall water quality, providing a more comfortable and efficient home environment.

However, the specific hardness level at which you may need a water softener can vary based on a variety of factors:

  • Household preferences: Some people may notice the effects of hard water (such as soap scum, scale buildup, and difficulty lathering) at lower levels of hardness, while others may tolerate it to a higher degree.
  • Appliance longevity: The hardness level at which you might want to consider a water softener could be influenced by the appliances you have and their maintenance requirements.
  • Cleaning efficiency: Hard water can make cleaning tasks more difficult and less effective. If you find that cleaning is a challenge even with regular cleaning products, you might consider a water softener.
  • Personal comfort: Some people prefer the feel of softened water on their skin and hair, which can be more noticeable at higher hardness levels.
  • Plumbing concerns: If you’re concerned about the impact of hard water on your plumbing system, you might consider a water softener.

What Does the Water Softener Hardness Number Mean?

By now, you might be asking yourself, what’s the deal with GPG numbers, and how do they help me sort out my water hardness issues? 

The hardness number refers to the capacity of the water softener to remove hardness minerals, primarily calcium and magnesium ions, from the water before the softener needs to regenerate or “recharge” itself. Grains per gallon (GPG) represents the total amount of dissolved minerals that the water softener can effectively remove before it requires regeneration.

Here’s a breakdown of what the hardness number for water softeners means:

Grains per gallon

The hardness number is expressed in grains of hardness minerals that a water softener can remove from one gallon of water. One grain is equivalent to about 17.1 milligrams of calcium carbonate (CaCO3). 

So, if a water softener has a hardness capacity of 30,000 grains, it means it can remove a total of 30,000 grains of hardness minerals from the water before it needs to regenerate.

Capacity and regeneration

As water passes through the resin bed inside the water softener tank, the resin beads exchange sodium ions for calcium and magnesium ions, effectively softening the water. 

Over time, the resin becomes saturated with hardness minerals and needs to be regenerated. During regeneration, a brine solution flushes out the accumulated minerals and recharges the resin beads with sodium ions, restoring the softening capacity of the water softener.

Matching household needs

The hardness number of a water softener should ideally match the specific hardness of the water in your area and the water consumption needs of your household. Choose a water softener with an appropriate hardness number to ensure it can effectively soften your water without requiring frequent regenerations or running out of softening capacity.

How to Test Your Water Hardness Level

It’s important to test your water hardness level before investing in a whole house water softener. To test for water hardness at home, you can use a water hardness test kit, typically available at hardware stores or online. Fill a clean container with a water sample, then follow the kit’s instructions to add the provided testing reagents. 

The reagents will cause a color change in the water, which you can compare to the hard water test strip color chart to determine the hardness level in terms of grains per gallon or parts per million of calcium carbonate. 

This simple and quick process will help you assess the hardness of your water and decide if a water softener or other treatment is needed based on your preferences and household needs.

Why You Should Know Your Water Hardness

Instead of adding a water softener just because 80% or more of American homes have hard water, use the above hardness scale to determine if you need one. Knowing your exact hardness level will help you understand and manage the mineral content in your water supply. Here’s what knowing your hardness can help with:

Assessment and awareness

The water hardness scale allows you to quickly assess the hardness of your water based on readily available measurements. This awareness helps homeowners understand the quality of their water and the potential impacts it can have on various aspects of daily life, from cleaning and bathing to appliance maintenance.


Armed with the information from a water hardness chart, people can make informed decisions about water treatment options. They can determine whether a water softener or other treatment methods are necessary to alleviate the negative effects of hard water.

Appliance longevity

Understanding the hardness of water is crucial for maintaining the longevity and efficiency of household appliances. Appliances like water heaters, dishwashers, and washing machines are susceptible to scale buildup from hard water minerals. 

By consulting a water hardness scale, homeowners can identify whether their water is in the range that could potentially damage appliances, prompting them to take preventive measures such as installing a water softener.


The water hardness scale helps homeowners avoid unnecessary expenses. Rather than treating water that is already at an acceptable softness level, individuals can tailor their water treatment approach to match the actual hardness of their water supply. This prevents overspending on water treatment solutions that might not be required.

Health and comfort

By referencing a water hardness chart, individuals can address potential dry skin and hair concerns caused by hard water, ensuring a more pleasant bathing experience.


Now that you’ve got my handy hardness chart, you’re armed with the knowledge to make smart choices for your home. If your water falls into the “hard” or “very hard” categories on the scale, it might be time to consider a water softener. 

It’s like giving your water a spa day — the soft water helps keep your skin happy, your dishes spotless, and your appliances humming along smoothly. So, whether it’s a relaxing shower or a sparkling clean kitchen you’re after, remember, a water softener could be your secret weapon for a more comfortable and efficient home.

If you’ve decided you need a water softener, read my review of the best water softeners to help you find the right one for your home.

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