Can I Use Rock Salt for My Water Softener? (Expert’s Advice)

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Rock salt is widely available and cheap to buy, so you might be wondering whether you can use rock salt instead of other types of softening salt in your water softener’s brine tank.

In this guide, we’ve answered the question, “Can I use rock salt in my softener?” We’ve also discussed the importance of the type of salt you use in your softener, and discussed the differences between water softener salt and rock salt.

📌 Key Takeaways:

  • You can use rock salt in a water softener, but we don’t recommend this salt type because of its lower purity percentage.
  • Rock salt contains up to 10% impurities, which accumulate in the salt keeper, potentially causing blockages and reducing the system’s efficiency.
  • Better alternatives to rock salt are high-purity salts, like evaporated salt and solar salt.

🤔 Why Is Salt Type Important In A Water Softener?

Before we discuss the suitability of rock salt for water softeners, let’s look at why salt type is important in the first place.

The type of salt used in a water softener is more important than you might think. The salt you use in your softener has an impact on the effectiveness and longevity of the water softening process.

As you’ll likely know, water softeners work by replacing calcium and magnesium ions in hard water with sodium ions from the salt. The salt undergoes a process called ion exchange, which regenerates the resin beads softener, removing hardness minerals.

Choosing the right type of salt allows for efficient ion exchange softening and maintains the softening capacity of the resin beads.

Different salt types have different levels of purity – essentially, some have more insoluble impurities than others. Impurities in the salt cause residue and sediment to build up in the water softener, reducing the system’s efficiency and potentially causing maintenance issues.

So, selecting a high-quality salt type that dissolves cleanly and leaves minimal residue is essential to optimize your water softener’s performance and extend its lifespan.

Water softener salt in brine tank ready for use

🚿 Is Rock Salt Okay To Use In A Water Softener?

Yes, rock salt is okay to use in a water softener, but it’s certainly not the best of your options, and we don’t personally recommend it for this purpose.

Rock salt is technically a type of water softener salt because, unlike other salt types (e.g. table salt), you can use it in your water softener and it’ll serve its intended purpose during the ion exchange process.

But while rock salt can be used in a water softener in a technical sense, it’s important to consider its potential drawbacks.

Rock salt is less refined than other salt types (like solar salt or evaporated salt), which means it typically contains higher levels of impurities and insoluble materials.

As we discussed earlier, impurities in salt can accumulate in the brine tank and the resin beads of the water softener, reducing its efficiency and leading to costly maintenance and repairs.

Plus, rock salt tends to be slower to dissolve, which can affect the brine production and regeneration process – further hindering the softener’s efficiency.

If you choose to use rock salt in your water softener, you’ll need to increase your frequency of cleaning and maintenance to prevent clogs, keep the salt brine tank and lines clean, and maintain the system’s effectiveness.

However, for optimal performance and minimal maintenance, we recommend using pure sodium chloride, avoiding additives and impurities in your softener salt as much as possible, enabling the salt to dissolve more readily and support your softener’s performance.

🔎 Is Water Softener Salt The Same As Rock Salt?

Yes, water softener salt is the same as rock salt because rock salt is one of the types of salt that’s marketed for use in a water softening system.

However, some people argue that rock salts, as well as a few other types of water softener salts (including salt blocks), aren’t actually suitable for use in water softeners due to their higher impurity percentage.

Rock salt contains up to 10% of impurities. When the sodium dissolves in water, insoluble matter ends up accumulating in the brine tank. If you want to achieve maximum brine formation in your softener, look at the higher-purity water softener salts, like evaporated salt and solar salt.

Rock salt in a spoon

⚖️ Pros And Cons Of Rock Salt For Water Softeners

Let’s take a look at the main benefits and setbacks of using rock salt in your water softening system:


  • Affordable – Its high impurity percentage makes rock salt cheaper than other softener salts.
  • Widely available – You can find rock salt in most grocery or big-box stores, as well as online marketplaces.


  • Least pure softener salt – Rock salt only contains around 90-97% sodium, so it doesn’t allow for the most efficient softening performance.
  • Increases salt usage – You’ll get through salt at a faster rate because there’s less salt and more impurities per bag.
  • Increases softener maintenance requirements – Impurities will accumulate rapidly in the brine tank, and you’ll need to clean it more often than if you used a pure salt.

💯 Best Alternatives To Rock Salt In Water Softeners

There are two types of salt that we recommend using in your softener:

  1. Evaporated salt pellets – Usually has a purity of up to 99.9%, making it the purest water softener salt you can buy
  2. Solar salt – Usually contains greater than 99.5% sodium chloride

Both evaporated and solar salt are more expensive than rock salts, but they help to maintain the performance and longevity of your water softener system, so a higher investment in salt means you can save money and effort on softener maintenance in the future.

Are salt crystals or pellets best for a softener tank? Salt pellets are more effective than crystals and dissolve better in water. They’re also less likely to contain additives, so we recommend water softener pellets for most people.

If you can’t or don’t want to use sodium chloride in your softener, you can also consider potassium chloride.

Potassium chloride works the same as sodium chloride to soften water (although you’ll need to increase your water hardness by about 20% for the same results). Again, look for a high-purity product – potassium chloride pellets are best.

Adding salt to a water softener brine tank

📑 Final Word

Regardless of whether you use rock salt or any other type of softener salt, you’ll still end up with a softened water supply. The type of salt you use won’t affect your water quality.

However, if you buy softener salt with a higher purity, you’ll protect the softener resin and brine tank, so our advice is to go for pure salt whenever possible.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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