Neutralizing Rainwater with a Calcite Blend Neutralizer

While most of our letters come from users of well and city water, some are from customers who rely on rainwater at home.

Rainwater often has a low pH when first collected, which can lead to copper leaching in cistern systems due to its acidity. One rainwater user recently contacted us with this issue, so we’re sharing our response for others with similar concerns.

Introduction to Neutralizing Filters

Neutralizing filters are essential water treatment systems that raise the pH of acidic water. They are commonly used in homes with low-pH water, especially from rainwater collection or shallow wells. These systems use calcite, a natural form of calcium carbonate, to safely correct pH levels and protect plumbing and appliances from corrosion.

How Neutralizing Filters Work

As acidic water passes through a calcite media bed, the calcite dissolves slowly and increases the water’s pH. This process helps maintain safe and balanced water chemistry throughout the home. However, using calcite can also increase water hardness, so pairing the system with a water softener may be recommended.

Key System Components and Considerations

• Calcite media should be NSF-certified for safe use in drinking water systems.
• Upflow neutralizers often use screened white marble, which minimizes metal leaching and improves water clarity.
• Service flow rate affects the filter's efficiency. A correctly sized system ensures optimal performance.
• Backwash filters need periodic maintenance. Replenishing calcite and allowing for proper bed expansion will keep the system running effectively.
• In some cases, Corosex (magnesium oxide) may be blended with calcite. However, Corosex alone can overcorrect pH, so careful blending is essential.

Rainwater is Acidic

If you are experiencing acidic rainwater—or worse, copper leaching due to acidic rainwater—consider installing a calcite blend neutralizer. We have helped many customers with rainwater problems, and this solution always resolves the issue.

For users in remote areas, we recommend using a manual backwash or an upflow type calcite blend neutralizer, which allows you to avoid unnecessary backwash cycles and save energy, water, and money.

Our neutralizer systems, equipped with calcite media, are well-suited for treating acidic rainwater.   The natural white eliminates acidic water by slowly dissolving Calcite (calcium carbonate) into the water as it flows through the filter.

How Calcite Works

Calcite dissolves slowly in acidic water, releasing calcium and magnesium ions that raise the pH. It’s typically placed in a backwashing filter to maximize contact with water, ensuring efficient neutralization.

As water flows through the media, the calcium carbonate dissolves, correcting the pH and producing non-corrosive water safe for plumbing. One major benefit of calcite is its self-limiting action—it raises the pH just enough to reach a safe, non-corrosive level without over-correcting. It’s most effective for water with a pH between 6.0 and 6.9.

For very acidic water, calcite can be blended with Corosex (magnesium oxide) for stronger pH correction. Since calcite is a natural mineral, it’s a non-toxic, eco-friendly option.

It’s also cost-effective, long-lasting, reusable, and compatible with other water treatment systems like acid neutralizers. Using calcite helps protect plumbing and appliances while improving overall water quality.

Calcite's Calcium Carbonate Neutralizes Acidic Water

For users in remote areas, we recommend a manual backwash or an upflow type calcite blend neutralizer, which allows you to avoid unnecessary backwash cycles and save energy, water, and money. It is important to monitor service flow rates for optimal performance. Additionally, you will need to add calcite periodically to maintain the system's effectiveness. Be aware of the potential for backwash bed expansion in upflow neutralizers. The inclusion of a bypass valve in the installation ensures easy connections to water lines.

Our neutralizer systems, equipped with calcite media, are well-suited for treating acidic rainwater. The natural white eliminates acidic water by slowly dissolving Calcite (calcium carbonate) into the water as it flows through the filter.

Bacteria and Parasites

When water runs over the roof, it can pick up bacteria and parasites from animal and bird droppings.  To make the water safe for drinking, we recommend as a final stage the Nano-Ceram Bacteria Filter. 

This uses a unique and patented electro-positive filtration technology.  The NanoCeram  purifier systems are certified for NSF P231, NSF 42, and NSF 53.

Developed with NASA technology, our Nano-Ceram nano-fiber filters remove bacteria, viruses, and turbidity.   7.5 log removal of E. coli, 99.5% endotoxin removal, and 6 log removal of viruses.   Removes cysts and parasites.

You might also consider installing a UV sterilizer to treat your rainwater. UV sterilizers are very popular treatment systems for rainwater users on cisterns, as they will kill any bacteria that might come from your catchment device (presumably your roof).

Our  sterilizers are great for users in remote areas, too, as they come with an external power supply and lamps rated for 9000 hours of life.

If you decide to use a UV sterilizer system, it should be installed before the neutralizer to prevent calcium minerals from the neutralizer from collecting on the UV quartz sle

eve. We also recommend installing the Nano-Ceram bacteria filter to remove any cysts and dead bacteria after the UV sterilizer.

If you're experiencing acidic rainwater and copper leaching, we're confident that these systems will resolve your issue.

For any further questions or comments regarding rain or well water treatment methods, please email us at support@cleanwaterstore.com, use our online contact form.

Thanks for reading!