Best Calcium Water Filter

Updated on:
April 18, 2024

While you definitely want to eat foods high in calcium, you might be less likely to want it in your water, hence why you’ve clicked on a post about the best calcium water filter. 

Calcium is one of two minerals that cause hard water. Along with magnesium, calcium can cause a slew of issues around the home. To effectively combat hard water, the right water treatment system or water filter is crucial. 

Two systems capable of removing calcium from water include reverse osmosis filters and ion exchange water softeners. So, let’s explore the differences between reverse osmosis and water softeners, so you can decide which water filter best suits your needs for removing calcium.

Key Takeaways

  • Calcium in water contributes to water hardness, which can damage appliances, cause scale buildup, irritate skin, and make cleaning harder.
  • Water treatment systems can remove calcium from water, but some do so better than others.
  • Ion exchange water softeners are the most-effective solution to excess calcium minerals, but reverse osmosis also removes minerals, including ones that don’t cause problems.
  • Which system you choose to tackle your calcium problem will depend on your level of water hardness, your home’s size, and other concerns specific to your needs.

What’s Wrong With Calcium in Your Water?

As our resident water specialist, James Layton, always says, “Calcium buildup isn’t just about spots on your dishes; it’s the hidden damage to your pipes and appliances that poses the real threat.”

In water, calcium exists in the form of dissolved calcium carbonate. This dissolved calcium, as well as magnesium, creates what’s known as “hard water.” When hard water flows through plumbing fixtures and appliances, it leaves behind mineral deposits, commonly known as limescale or scale buildup. 

Over time, these deposits can accumulate within pipes, faucets, showerheads, and even within the internal components of appliances like dishwashers, washing machines, and water heaters. The result is less-efficient functioning of your appliances and, eventually, malfunction.

Hard water has implications beyond pipes, fixtures, and appliances though.

Water that’s high in hardness minerals doesn’t lather soap and detergent well enough, meaning it requires more of these products to get dishes, laundry, and even bodies clean. Your dishes may come out of your dishwasher bearing a chalky film, and your laundry may not feel and smell as fresh as you’d prefer.

Additionally, hard water minerals can actually strip natural oils from your skin and prevent them doing their job — protecting your skin. These same minerals can build up in your hair, preventing proper rinsing of shampoo and conditioner and also making your hair dry, dull, and brittle.

With all that, it’s no wonder people have invented ways to remove these minerals from water.

Where Does the Calcium in Our Water Supply Come From?

As groundwater travels through calcium-rich limestone and gypsum, it picks up and dissolves this calcium. Calcium and other dissolved minerals the water has picked up then become part of the water supply. 

Human activities can also introduce calcium into water sources. For instance, agricultural practices, such as the application of lime to soil for pH adjustment, can increase levels of calcium in surface runoff, which eventually finds its way into aquifers, then wells. 

However, natural sources remain the primary contributors to calcium content in most water supplies.

How Do You Purify Calcium Water?

There are two main methods for purifying calcium water: reverse osmosis and ion exchange.

Reverse osmosis (RO) uses physical filtration to remove calcium. It forces water through a semipermeable membrane that removes calcium along with a wide range of other contaminants.

Rather than physical removal, ion exchange technology uses a chemical reaction by replacing calcium (and magnesium, the other hardness mineral) ions with sodium ions (or sometimes potassium). To achieve this, water passes through a negatively charged resin bed that attracts the positively charged calcium ions, pulling them from the water. Then, sodium ions flush the resin bed, replacing the calcium ions, which get washed away as wastewater.

Types of Water Filters for Calcium Removal

According to James, “Not all water filters remove calcium; make sure the one you choose is up to the task.” Before you choose either an RO system or a water softener, it’s important that you understand the capabilities and limitations of each system.

Reverse osmosis system

Reverse osmosis comes mainly in one of two forms: under-sink systems and whole-house systems. When it comes to protecting your whole home from the effects of calcium, you’ll need a whole-house system. An under-sink system, though cheaper, will do nothing to protect your appliances, fixtures, laundry, skin, or hair.

RO systems include multiple stages of filtration to ensure the water you consume is safe and free from over 1,000 contaminants, including calcium. Before water reaches the RO membrane, it passes through pre-filters, usually activated carbon and sediment filters, designed to remove particles that could damage the RO membrane, as well as chlorine, chloramines, and foul tastes and odors.

The pre-filtered water is then forced through the semipermeable RO membrane under pressure. This membrane has tiny pores as small as 0.0001 microns, which can block most dissolved solids, including calcium and magnesium ions. As water molecules pass through the membrane, these ions are left behind, effectively reducing the concentration of calcium in the water.

The rejected contaminants and dissolved solids are flushed away as wastewater, or “concentrate,” through a drain line. This process prevents the buildup of impurities on the membrane surface, ensuring its longevity and continued effectiveness.

After passing through the RO membrane, the purified water undergoes post-filtration using a second carbon filter to remove any remaining tastes, odors, or residual contaminants. Some manufacturers also include a UV purifier that removes bacteria and viruses to further enhance the quality of the water before it is delivered to your faucet.

The treated water is stored in a dedicated storage tank, which maintains a sufficient supply of purified water for on-demand use. When you open a faucet or appliance connected to the RO system, the purified water is distributed for consumption.

Reverse osmosis systems offer a powerful way to remove contaminants and minerals from your water supply. However, like any filtration system, they come with both advantages and disadvantages:


  1. Exceptional contaminant removal: RO systems are highly effective at removing a wide range of contaminants. This includes calcium and magnesium, responsible for hard water, as well as other minerals, such as iron, manganese, and fluoride. They also remove heavy metals, including arsenic, lead, and mercury. While not specifically designed for this purpose, RO membranes can also filter out some microbial contaminants, but RO is not a reliable method for solving serious microbial contamination.
  2. Improved taste and odor: By removing chlorine and organic compounds in the pre- and post-filtration stages, RO systems can significantly improve the taste and odor of your water.
  3. Reduced scale buildup: Since RO removes calcium and magnesium, the leading culprits behind scale buildup, it can help prevent scale formation in pipes, appliances, and fixtures like kettles and coffee makers.
  4. Low energy consumption: RO systems typically operate using household water pressure, requiring minimal energy consumption compared to other water treatment methods.


  1. Extremely expensive: In order to achieve your objective of controlling calcium’s effect on your appliances and fixtures using RO, you would need a whole-house reverse osmosis system. These run from $5,000 to $15,000 on average. You’ll also have to regularly replace the filter elements, including the activated carbon, sediment filters, and, less often, the RO membrane itself.
  2. Limited calcium removal: Unlike water softeners, whose primary role is to remove low and high levels of calcium and magnesium minerals from a variety of water sources, RO systems can only filter out low and moderate levels of these minerals. If the water contains an excessive amount of calcium and magnesium, the membrane can become clogged or fouled over time. This scaling on the membrane surface reduces water flow and efficiency and can also lead to membrane damage, affecting the system’s overall performance.
  3. Slower filtration process: The multistage filtration process in RO systems can be slower compared to other filtration methods, resulting in a limited flow rate and potentially longer wait times for purified water.
  4. Wastewater production: RO systems produce a significant amount of wastewater during the filtration process, typically generating several gallons of wastewater for every gallon of purified water produced.
  5. Reduced water pressure: The filtration process in RO systems can cause a slight decrease in water pressure, which may be noticeable in some households, particularly those with already low water pressure.
  6. Maintenance needs: RO systems require regular maintenance, including filter replacements and membrane cleaning. Be sure you’re comfortable with the upkeep before purchasing a system.
  7. Vulnerable to damage: The reason reverse osmosis can remove calcium from water is that the calcium carbonates are trapped by the reverse osmosis membrane. Unfortunately, they’re not always washed away by the backwash. Rather, they build up and reduce the efficiency and longevity of the membrane, which will require more-frequent replacement. In fact, some RO systems actually advise you to not use them with hard water.

Who are RO systems best for?

Whole-house RO systems are ideal for homeowners who want really pure water from every tap in the house, even the toilets, bathroom sinks, and showers. These systems remove 99% of contaminants, including calcium, nitrates, heavy metals, chemicals, and microorganisms.

While RO can remove calcium carbonates from both city water and well water, it’s really best for removing a wider range of contaminants, and it’s not the best treatment system for removing calcium because it has a limited capacity to do so and may be damaged by the calcium itself.

Water Softeners

Water softeners apply an ion exchange process to remove calcium and magnesium ions that cause hardness in water. The key components are the ion exchange resin — tiny plastic beads — and the brine solution consisting of dissolved sodium.

As the hard water enters the softener tank, it passes through the resin bed. The negatively charged resin beads attract and trap the positively charged calcium and magnesium ions. Softened water then flows through to the house.

When the beads become full of calcium and magnesium ions, a salty solution drawn from the separate brine tank swaps the stronger sodium ions for the mineral ions in a process called regeneration. This removes the hardness-causing minerals and replaces them with dissolved sodium ions, and the mineral-rich water is drained away as wastewater.

Most softeners automatically regenerate on a scheduled basis (typically between three and eight days, but modern, eco-friendly models can go even longer) to purge the built-up hardness minerals from the resin tank. By continuously cycling sodium for calcium and magnesium, the ion exchange resin allows the softener to effectively remove nearly all hardness from the water supply.

Here is a detailed list of the pros and cons of water softeners:


  1. Prevents scale buildup: Water softeners effectively remove calcium and magnesium ions from water, preventing the formation of scale buildup on plumbing fixtures, appliances, and surfaces. This helps keep faucets running smoothly and extends the lifespan of water heaters and other household appliances, reducing the need for repairs and replacements.
  2. Improved cleaning efficiency: Softened water lathers more easily with soap and detergent. This helps produce softer laundry, cleaner dishes, and reduces soap scum and residue on surfaces, resulting in cleaner and shinier fixtures and surfaces. And since you need less soap and detergent to do the job, it also saves you money.
  3. Protects skin and hair: Softened water is gentler on the skin and hair. This can help alleviate dryness, irritation, and itchiness commonly associated with hard water, leading to softer skin and healthier-looking hair.
  4. Energy efficiency: By preventing scale buildup in water heaters and appliances, water softeners can improve energy efficiency and reduce utility costs. Appliances operate more efficiently when free from mineral deposits, requiring less energy to heat water or run cycles.
  5. Improved taste (for some): While some people prefer the taste of hard water, others find it metallic or unpleasant. Softening can remove these minerals, potentially leading to a more palatable taste for some.
  6. Wastes less water than reverse osmosis: Reverse osmosis wastes water for every gallon of filtered water it produces, all day long, every day. If you’re using it throughout the home, that’s a great deal of water. Ion exchange, on the other hand, only wastes water when it regenerates the resin beads, which, for some homes, could be as infrequent as once a month.


  1. Maintenance requirements: Water softeners require regular maintenance, including refilling the salt reservoir, monitoring salt levels, and periodic regeneration cycles. Failure to maintain the system properly can lead to decreased efficiency and performance issues.
  2. Wastewater generation: The regeneration process of water softeners generates wastewater containing dissolved minerals and salts, which must be discharged properly. This can contribute to water wastage and may pose environmental concerns if not managed responsibly.
  3. Initial cost: Water softeners can have a significant up-front cost for purchase and installation, though not nearly as expensive as whole-house reverse osmosis systems. Additionally, ongoing expenses for salt refills and maintenance should be considered when evaluating the overall cost of ownership.
  4. Not a universal solution: Water softeners don’t address all water quality issues. They primarily target calcium and magnesium and won’t remove contaminants like chlorine, heavy metals, or bacteria. Depending on your needs and concerns, alternative water treatment options like point-of-use reverse osmosis systems or other drinking water filters might be suitable additions.
  5. Sodium content: Water softeners replace calcium and magnesium ions with sodium ions, increasing the sodium content in softened water. While the amount of sodium added is infinitesimal, it may be a concern for people on sodium-restricted diets. In such cases, a salt-free water softener/conditioner is a better option. This system neutralizes the calcium and magnesium ions without the need for salt, but it isn’t nearly as effective. 

Who are water softeners best for?

Water softeners benefit people living in regions with naturally occurring hard water, which is 85% of people in the United States. Homeowners in such areas often experience issues like inefficient soap lathering, damaged or poorly functioning appliances, irritated skin and dull hair, and unsightly mineral deposits on faucets and showerheads.

Families will appreciate the improved performance of detergents and elimination of water spots/scaling with softened water. Additionally, people with sensitive skin, eczema, or other skin conditions may find relief by using softened water, which is gentler and more hydrating. Softened water can also result in smoother, shinier hair and reduce the need for additional conditioning products.

However, an increasing number of state and local governments are banning salt-based water softeners due to the environmental implications of the brine flush. You’ll want to look up your region’s regulations before committing. Likewise, it is essential to consider the potential drawbacks, such as regular maintenance requirements, when deciding if a water softener is the right choice for your household. 

How to Choose the Right Filter for Your Home

Now that you understand how both reverse osmosis and water softeners tackle calcium in hard water, it’s time to decide which system is right for your home. Here are some key factors to consider when selecting the perfect calcium water filter:

1. Water hardness level

The first step is to understand the severity of your hard water problem. Get your water tested by a certified laboratory or use a home testing kit to determine the level of calcium hardness in your water supply. This will help you determine what size water softener you need or if you need a water softener at all.

For low or moderately hard water, or if you have concerns about other contaminants, an RO system might be sufficient. You just need to keep in mind that calcium and other hardness minerals will clog your RO membrane sooner and it will need to be replaced more often, adding to the cost of an already expensive system. 

For very hard water, a water softener will always be the better choice than RO due to its superior calcium removal capabilities, more reasonable up-front cost, and lower water waste.

2. Household size and water consumption

The number of people in your household directly impacts the daily water demand. Larger households require more treated water for drinking, cooking, and other purposes. A smaller household may find a smaller system is sufficient, while larger families will need a higher-capacity system. Consider the space available for installation. Some systems, especially water softeners, are bulkier and may not fit well in tight spaces.

These tables will help you determine what water softener grain capacity or reverse osmosis flow rate you need, based on the results of your water hardness test and the number of people or bathrooms in your home.

Water Softener Sizing Chart
Hardness in grains per gallon1–2 people3–4 people5–6 people7–8 people
5–10 gpg32,000 grains32,000 grains40,000 grains48,000 grains
11–20 gpg32,000 grains40,000 grains48,000 grains64,000 grains
21–30 gpg32,000 grains48,000 grains64,000 grains80,000 grains
31–40 gpg48,000 grains64,000 grains64,000 grains96,000 grains
41–50 gpg64,000 grains80,000 grains96,000 grains110,000 grains
51–75 gpg64,000 grains80,000 grains96,000 grains110,000 grains
76–100 gpg80,000 grains96,000 grains96,000 grains110,000 grains
Use this table to match your water test to your household size.

Reverse Osmosis Sizing Chart
1–2 bathrooms4–5 bathrooms5+ bathrooms
Flow rate200–300 gpd500–2,500 gpd4,000–7,000 gpd
Use this table to determine what flow rate you need from your RO system.

3. Budget and maintenance

The up-front cost differential between the two systems can be significant. 

A full-sized ion-exchange water softener is usually $1,000 to $3,000 on average for purchase and professional installation.

A whole-house reverse osmosis system, however (remember, we’re not talking just under the kitchen sink with one tap for RO water), can cost between $2,200 and $8,000 or as much as $18,000, and that’s not even factoring in all the wasted water you’ll pay for.

The long-term operating costs also vary. RO membranes need replacing every one to two years at $50–$100 each time, plus periodic filter changes, and the sediment and carbon filters need replacing more frequently than that. Water softeners have regular costs for replenishing salt/potassium pellets, but resin beds may need $300–$1,000 replacement only every 10–15 years. They also waste water, but not as much as reverse osmosis.

Overall, softeners tend to have lower lifetime operating expenses compared to RO systems.

4. Additional water concerns

As we’ve established, testing your water hardness level will help you determine whether a water softener alone is sufficient or if an RO system would be more appropriate. In addition to hardness, your water may contain other contaminants, such as heavy metals, bacteria, viruses, chemicals, or sediment. For extreme contamination, it may not be unreasonable to want clean RO water from every tap in the house.

Reverse osmosis systems are highly effective at removing a wide range of contaminants, providing comprehensive water treatment. On the other hand, water softeners are designed specifically to address water hardness and do not remove other impurities. 

If your water supply has multiple contaminants, an RO system or a combination of filtration methods may be necessary to ensure safe and clean drinking water. Just keep in mind that you can save money by installing a water softener for the whole house and an under-sink RO for drinking water only.

5. Local regulations

Local water regulations establish standards and guidelines for drinking water quality, including permissible levels of various contaminants and impurities. Before purchasing a calcium filter, it’s essential to understand the specific regulations governing your water supply to ensure compliance with these standards.

For one, some state and local governments have restrictions or requirements around the use of water softeners due to concerns over the environmental impact of the salt-based brine discharge. This salty wastewater can potentially disrupt septic systems or contaminate groundwater supplies if not properly handled. Areas with high water scarcity may also limit softener use to conserve water.

Additionally, proper permitting and compliance with local plumbing codes is essential, whether it’s an RO system or softener. Failure to follow regulations can lead to problems down the road.

Best Water Filter for Removing Calcium

If you need to completely eradicate calcium and magnesium from your water supply, then a salt-based water softener is your best choice. 

We’ve completed extensive research on water softeners and compiled a list of the best: Eight Best Water Softeners.

However, if your water test shows low levels of these minerals in your tap water and you want comprehensive water treatment for your entire house and you can afford it, then an RO system is your go-to solution. 

We’ve also researched reverse osmosis systems just as thoroughly as we have water softeners, and compiled a similar list of the best models you’ll find: Six Best Whole-House Reverse Osmosis Filters.


A water softener is the best solution to high levels of calcium in your water. Water softeners are extremely good at removing calcium, while reverse osmosis systems are just okay at it. A water softener costs less than a whole-house reverse osmosis system and wastes less water.

However, you only need to remove mild levels of calcium and you want pure water everywhere in your home, even the toilets — and you’re willing to pay for it — a whole-house reverse osmosis system will do it. 

Investing in the right calcium-removing filter not only protects your plumbing but can also extend the lifespan of water-using appliances and improve the overall quality of your home’s water supply. Take the time to carefully evaluate your options to ensure you select the most suitable solution for your home.

Frequently Asked Questions

What is the best filter to remove calcium?

The best filter to remove calcium from water is a water softener. Water softeners use ion exchange technology to replace calcium ions with sodium ions, effectively softening water and eliminating the problems associated with hard water.

What device removes calcium from water?

A water softener is a device specifically designed to remove calcium from water. It works by passing water through a resin bed, where calcium ions are exchanged for sodium ions. Another device that can remove calcium from water is a reverse osmosis system.

Does boiling water remove calcium?

Boiling water does not remove calcium but it does convert dissolved calcium into solid particles. This is an energy intensive process and not a practical way to soften water that is hard from dissolved calcium.

How do you reduce calcium in water naturally?

While there are no completely natural methods to significantly reduce calcium in water, some techniques can help lower its concentration. For example, using a distiller can separate water from minerals, including calcium, through evaporation and condensation. However, distillation is a slow and energy-consuming process. Another option is to use a natural water softener like citric acid, which can bind with calcium ions and prevent scale formation. However, these methods are not as effective or efficient as using a water softener.

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