Maintaining proper water balance is essential for ensuring a safe, comfortable, and enjoyable swimming experience in your pool. One crucial aspect of water balance is calcium hardness, which refers to the amount of dissolved calcium and magnesium minerals in your pool water. When calcium hardness levels become too high, it can lead to various problems, such as scaling, cloudy water, and reduced circulation efficiency.

This is where calcium hardness reducers come into play. In this comprehensive guide, we’ll explore what calcium hardness reducers are and how they work, and introduce you to the top products available in the market.

Calcium Hardness Reducer

What is Calcium Hardness?

Before delving into calcium hardness reducers, let’s first understand what calcium hardness is and why it matters in pool water balance. Calcium hardness measures the total dissolved calcium and magnesium in your pool water. These minerals can come from various sources, such as the fill water, pool chemicals, and the environment (e.g., rain, dust).

The ideal range for calcium hardness in pool water is between 200 and 400 parts per million (ppm). When calcium hardness levels fall below 200 ppm, the water becomes “soft” and can cause corrosion of pool surfaces and equipment. On the other hand, when calcium hardness levels exceed 400 ppm, the water becomes “hard” and can lead to scaling, cloudy water, and reduced circulation efficiency.

What is a Calcium Hardness Reducer?

A calcium hardness reducer is a chemical solution designed to lower the calcium hardness levels in your pool water. These products work by sequestering or chelating the excess calcium and magnesium ions, keeping them suspended in the water and preventing them from forming scale deposits on pool surfaces and equipment.

Calcium hardness reducers typically contain active ingredients such as:

  • Phosphates
  • Polycarboxylates
  • HEDP (Hydroxyethylidene Diphosphonic Acid)
  • EDTA (Ethylenediaminetetraacetic Acid)

These compounds effectively bind to the calcium and magnesium ions, making them less likely to precipitate out of the water and form scale.

When to Use a Calcium Hardness Reducer

You should consider using a calcium hardness reducer when:

  1. Your pool water tests reveal calcium hardness levels consistently above 400 ppm.
  2. You notice signs of scaling on pool surfaces, such as rough, white, or grayish deposits on tile, walls, or equipment.
  3. Your pool water appears cloudy or hazy due to high calcium hardness levels.
  4. Due to scale buildup, You experience reduced circulation efficiency or pressure in your pool system.

It’s important to note that while calcium hardness reducers can help manage high calcium levels, they should be used with regular water testing and balancing. Addressing the root cause of high calcium hardness, such as using a water source with lower mineral content or adjusting other water chemistry parameters, is crucial for long-term pool health.

Top Calcium Hardness Reducer Products

Top Calcium Hardness Reducer Products

When choosing a calcium hardness reducer for your pool, look for products from reputable brands formulated to effectively lower calcium levels without negatively impacting other water chemistry parameters. Here are some of the top calcium hardness reducer products available in the market:

  1. Clorox Pool & Spa Super Water Softener: This powerful calcium hardness reducer is designed to quickly and effectively lower calcium levels in your pool water. It is compatible with all pool types and sanitizers, making it a versatile choice for pool owners.
  2. Leslie’s Hardness Plus: Leslie’s Hardness Plus is a fast-acting calcium hardness reducer that helps prevent scale formation and protects your pool surfaces and equipment from the damaging effects of high calcium levels. It is easy to use and suitable for both inground and above-ground pools.
  3. Orenda PR-10,000 Phosphate Remover: While primarily marketed as a phosphate remover, Orenda PR-10,000 also acts as an effective calcium hardness reducer. This product uses a unique blend of rare earth minerals to sequester calcium, magnesium, and other metals, preventing scale formation and maintaining water clarity.
  4. Stain and Scale Control by Orenda Technologies: This comprehensive water treatment solution reduces calcium hardness and helps prevent stains and scale formation caused by high mineral content. It is compatible with all pool types and sanitizers, making it a convenient choice for pool owners.
  5. Doheny’s All-Natural Stain Away: Doheny’s All-Natural Stain Away is an eco-friendly calcium hardness reducer that uses natural chelating agents to lower calcium levels without harsh chemicals. It is safe for all pool types and helps maintain balanced water chemistry.

How to Use Calcium Hardness Reducers

Using calcium hardness reducers is relatively straightforward, but following the manufacturer’s instructions carefully is essential to ensure the best results. Generally, the process involves the following steps:

  1. Test your pool water to determine the calcium hardness level and the reducer needed.
  2. With the pool pump running, add the recommended dosage of calcium hardness reducer to the pool water, distributing it evenly around the perimeter.
  3. Allow the pool pump to run for at least 24 hours to ensure thorough distribution and give the reducer time to work.
  4. Retest the calcium hardness level after 24-48 hours and repeat the treatment if necessary, following the manufacturer’s maximum dosage and frequency guidelines.

When using calcium hardness reducers, it’s crucial to maintain proper water balance and monitor other chemistry parameters, such as pH and total alkalinity. Regular water testing and adjustments will help ensure the best results and prevent potential issues related to imbalanced water chemistry.

Frequently Asked Questions (FAQs)

Can I use a calcium hardness reducer in a saltwater pool?

Yes, most calcium hardness reducers are compatible with saltwater pool systems. However, always check the product label or consult with the manufacturer to ensure the specific reducer you choose is suitable for saltwater pools.

How often should I use a calcium hardness reducer?

The frequency of using a calcium hardness reducer depends on factors such as your pool’s calcium hardness level, water source, and environmental conditions. As a general guideline, monitoring calcium hardness levels monthly and using a reducer as needed to maintain levels within the ideal range of 200-400 ppm is recommended.

Will a calcium hardness reducer affect my pool’s pH or alkalinity?

Some calcium hardness reducers may slightly impact pH or alkalinity levels, depending on their formulation. However, most high-quality reducers are designed to minimize these effects. It’s essential to regularly test and adjust your pool’s pH and alkalinity to maintain proper water balance.

Can I preventively use a calcium hardness reducer, even if my calcium levels are not high?

While it’s generally unnecessary to preventively use a calcium hardness reducer, some pool owners choose to do so in areas with hard water or high mineral content. However, not overusing these products is crucial, as excessively low calcium hardness can lead to corrosion and other water balance issues.

Is it safe to swim in the pool after using a calcium hardness reducer?

In most cases, swimming in the pool after using a calcium hardness reducer is safe, provided you have followed the manufacturer’s instructions and allowed sufficient time for the product to circulate. However, it’s always best to refer to the specific product guidelines and test your water chemistry before swimming to ensure optimal water quality and safety.


Proper calcium hardness ensures a well-balanced, safe, and enjoyable pool environment. Understanding the role of calcium hardness in water chemistry and using high-quality calcium hardness reducers when needed can prevent issues such as scaling, cloudy water, and reduced circulation efficiency.

Regularly test your pool water, follow the manufacturer’s instructions when using calcium hardness reducers, and maintain overall water balance for the best results. If you have any doubts or concerns about your pool’s water chemistry, don’t hesitate to consult with a professional pool service provider for guidance and support.

With the right knowledge, tools, and products, you can effectively manage calcium hardness and enjoy a sparkling, clean, well-maintained pool all season long.