Reverse osmosis (RO) is one of the most trusted ways to get exceptionally clean drinking water—but many people still ask the same core question: does reverse osmosis remove minerals, and if so, what does that mean for health, taste, and daily use? RO is well-known for removing harmful contaminants, but it also filters out beneficial and essential minerals such as calcium and magnesium. That’s why understanding what RO removes, what it leaves behind, and when remineralization makes sense is key to choosing the right system for safe drinking water.
In this guide, you’ll get clear, practical answers. You’ll learn how RO membranes work, how effectively they remove minerals and other contaminants, and why add-ons like activated carbon or UV matter for chlorine and microbial safety. We’ll also explain when RO water can taste “flat,” how remineralization or alkaline stages restore balance, and what to look for when comparing systems. If you’ve ever wondered whether RO water is too low in minerals or whether you need to add some back, this guide breaks it all down—simply, accurately, and with real numbers you can use.
Quick Answers: Does Reverse Osmosis Remove Minerals?
Wondering what reverse osmosis can remove from your water and what it can’t? RO is one of the most common water treatment methods used in homes and offices. Its system uses a membrane to filter most minerals from water, along with heavy metals and other contaminants.
Snapshot findings and removal rates (fast facts)
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Does reverse osmosis remove minerals? RO water contains very few minerals; RO commonly removes about 92–99% of dissolved minerals.
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Does reverse osmosis remove calcium? Yes, RO does remove calcium and magnesium. Typical lab and field data show:
- Calcium removal: about 97%
- Magnesium removal: about 96%
- Fluoride removal: about 95%
- Other ions (iron, zinc, phosphate, sodium, sulfate, nitrate): usually 90–95%
Will reverse osmosis remove bacteria? The membrane can reject bacteria and many viruses when intact. For reliable microbiological safety, add a UV light or another disinfection step.
Will reverse osmosis remove chlorine? The RO membrane alone is not good at removing free chlorine or chloramine. A high-quality activated carbon prefilter is needed to remove chlorine and protect the membrane from damage.
To put it simply, RO blocks water-soluble ions and large molecules. That includes hardness minerals (calcium and magnesium), many salts like sodium and sulfate, and a wide range of metals and chemicals. Common categories include:
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Inorganic ions: calcium, magnesium, sodium, nitrate, sulfate, fluoride, chloride
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Heavy metals: lead, arsenic, chromium, mercury, cadmium, copper
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Organic chemicals: many pesticides and VOCs. PFAS are often reduced best with a carbon + RO combination
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Particulates: fine sediments and microplastics
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Taste/odor-causing dissolved solids (overall TDS drops sharply)
What RO doesn’t remove efficiently on its own
RO is powerful, but not perfect. A few points to keep in mind:
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Chlorine and chloramine pass through the membrane and can damage it. Activated carbon (and for chloramine, catalytic carbon) is the standard fix.
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Some dissolved gases like carbon dioxide can pass. CO2 can lower pH.
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Microbial protection depends on membrane integrity and the cleanliness of storage and tubing. If you have any microbiological risk, add UV or ultrafiltration after the RO tank.
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So, does RO remove chlorine—or the carbon filter? The carbon filter does the heavy lifting for chlorine and chloramine, while the RO membrane handles most dissolved salts and metals.
Is RO water safe to drink every day?
Yes, RO water is safe when the system is properly installed and maintained. Because RO water has very low mineral content, you might choose remineralization to improve taste, raise alkalinity, and support a more balanced mineral profile in your daily drinking water. Whether you need to add minerals depends on your diet, local water quality, and personal taste.
What Does Reverse Osmosis Do?
Reverse osmosis might sound technical, but the process is easier to understand than it seems. RO pushes water through a special membrane that lets water molecules through while blocking most dissolved salts, metals, and other contaminants. What comes out is clean drinking water, while the concentrated waste carries away the impurities. Let’s take a closer look at how each stage works and what affects the system’s performance.
The RO process explained
RO uses pressure to push water through a semipermeable membrane. Water molecules pass; most dissolved ions and larger contaminants do not. The flow skims along the membrane (crossflow), so the surface keeps cleaning itself.
A typical home RO setup has stages that look like this:
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Sediment filter: catches sand, rust, and fine particles
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Activated carbon filter: removes chlorine and many organic chemicals; protects the RO membrane
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RO membrane: rejects dissolved salts, metals, and many other contaminants
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Post-filter (usually carbon): polishes taste before the faucet
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Storage tank and dedicated faucet: holds purified water (called “permeate”)
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Waste line: carries the concentrated reject stream (called “brine” or “concentrate”) to drain
The system produces two streams: permeate (the water you drink) and concentrate (the waste stream with the removed contaminants).
Factors that affect removal efficiency
RO performance changes with operating conditions and water quality. A few key drivers:
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Pressure: Higher pressure improves rejection and flow through the membrane.
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Temperature: Warmer water flows faster through the membrane; very cold water slows production.
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Feedwater TDS: Higher dissolved solids can reduce flow and rejection.
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Membrane age and fouling: Scale or biofilm on the membrane lowers performance.
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Carbon prefilter quality: Strong carbon protects from chlorine; catalytic carbon helps on chloramine.
Terms you might see in manuals:
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Recovery ratio: percent of feedwater that becomes permeate
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Permeate flow: how much purified water the system makes
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Scaling and fouling: mineral build-up or biological growth that blocks the membrane
Certifications and performance claims
If you want proof of performance, look for systems certified to NSF/ANSI Standard 58. This standard covers TDS reduction and may include specific claims like lead or fluoride reduction. You can also ask for independent lab reports that match your local water issues.
Mineral Content, Health, and Taste
Many people ask does reverse osmosis remove minerals, and that matters because minerals in water do more than just make it “hard”—they contribute to taste, pH balance, and overall daily mineral intake. RO produces very clean water, but it removes most of these minerals, which is why some users opt for alkaline water or remineralization. Let’s explore what that means for health, flavor, and whether adding minerals back might be a good idea.
Water as a mineral source vs. diet
So, does RO water have minerals? Very little. RO removes most calcium and magnesium—the minerals that make water “hard.” Regular tap water, especially in hard-water regions, can provide a modest amount of these minerals each day. When you switch to low TDS water from RO, your water no longer contributes much to daily calcium and magnesium intake. This is not always a problem if your diet already covers these needs, but it does change the equation for some people.
Research signals and case observations
Public health bodies and research groups have studied low-mineral water and its effects. According to the World Health Organization (WHO), long-term consumption of demineralized water may reduce daily intake of essential minerals such as calcium and magnesium and may influence taste and overall mineral balance. This aligns with observations that when communities shift suddenly to very low-mineral water, some people report short-term symptoms such as tiredness or muscle cramps. In some settings, short-term complaints such as tiredness or muscle cramps have been reported when communities suddenly shifted to very low-mineral water. The strength of evidence varies, and diet plays a major role, but the take-home message is simple: RO water is safe, yet very low in calcium and magnesium. If your water used to be a meaningful source of minerals, you may wish to remineralize for taste and balance.
Taste, pH, and corrosion
Have you ever tasted water that seems “flat”? That’s common with very low TDS. Minerals add mouthfeel and a natural sweetness. Low-mineral water also has low alkalinity, so the pH can drift and the water has less buffering capacity. In plumbing, RO water reduces scale (good for appliances), but very low alkalinity can raise corrosion risk in some setups. Remineralization increases alkalinity and tends to improve taste and stability.
Tap vs RO vs remineralized (typical ranges)
Use this as a general reference. Your numbers will vary by region and system.
| Water Type | Calcium (mg/L) | Magnesium (mg/L) | TDS (mg/L) | Alkalinity (mg/L as CaCO3) | pH |
| Typical municipal tap | 20–80 | 5–30 | 150–500 | 50–200 | 7.0–8.2 |
| RO permeate | <2–5 | <1–3 | 5–50 | <10–20 | 5.8–7.2 |
| Remineralized RO | 20–40 | 10–20 | 80–150 | 40–100 | 7.2–8.0 |
Values shown are typical targets and ranges, not strict rules.
What Does Reverse Osmosis Remove
Reverse osmosis water filtration system is a powerful filtration method, but what exactly does it remove from your water? RO tackles dissolved salts, heavy metals, and many contaminants that affect taste, odor, and safety. Some substances, like chlorine, certain gases, and PFAS, may need extra treatment to be fully removed. Let’s take a closer look at the main categories of contaminants and how effectively reverse osmosis water system handles them.
Inorganic ions and metals
RO systems are known for strong rejection of dissolved salts and metals. This includes lead, arsenic, chromium, mercury, copper, nitrate/nitrite, sulfate, sodium, and fluoride. Typical reductions are often greater than 90% for many dissolved ions, and total dissolved solids (TDS) drop sharply. Actual numbers depend on membrane condition, water temperature, pressure, and feedwater TDS.
Organic chemicals and emerging contaminants
Many pesticides, herbicides, and VOCs are reduced by the RO membrane and even more by a carbon + RO combo. PFAS, a class of “forever chemicals,” are reduced best by pairing high-quality activated carbon with RO. If PFAS are a concern in your area, ask for lab data that shows both carbon and RO performance.
Aesthetic and TDS reductions
Using a reverse osmosis system improves taste and odor by removing both dissolved solids and many organic compounds. Hard water scale disappears because calcium and magnesium are mostly removed. You may notice cleaner coffee and tea flavors. Some people, however, find very low TDS “too flat,” which is why remineralization has become a popular add-on.
Removal spectrum (quick comparison)
| Category | Typical Reduction | Notes (assist if needed) |
| Hardness (Ca, Mg) | ~96–97% | Reduces scaling |
| Fluoride | ~90–95% | Confirm with NSF/ANSI 58 |
| Lead, arsenic, chromium, nitrate | >90% | Check spec sheet for ion-specific |
| Chlorine/chloramine | Carbon-dependent | Use activated/catalytic carbon |
| Pesticides, VOCs | High with carbon+RO | Carbon improves RO performance |
| Bacteria/viruses | High (membrane) | Add UV/UF for assurance |
| PFAS | Often high with carbon+RO | Request lab data |
| CO2 and some gases | Variable | May pass; affects pH |
Remineralization After Reverse Osmosis Filtration: Why, When, How
After reverse osmosis, water is extremely pure but also very low in minerals. Remineralization is a simple way to restore taste, adjust pH and alkalinity, and even add small amounts of calcium and magnesium back into your daily intake. Let’s explore why people choose to remineralize, the common methods, and how to find the right balance for taste and health.
Why remineralize?
People remineralize RO water for three main reasons. First, taste. Adding beneficial minerals can improve flavor and quality of the water. A touch of mineral content also gives water body and balance. Second, pH and alkalinity. Minerals raise buffering capacity, which helps stabilize pH and reduce corrosion risk in plumbing and storage tanks. Third, daily mineral intake. Drinking water can contribute small amounts of calcium and magnesium, which may matter if your diet is low in these minerals. Do I need to add minerals to reverse osmosis water? You don’t have to, but many people prefer the taste and balance, and it’s a simple, low-cost upgrade.
Methods and media options
Common ways to add minerals back include:
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Calcite (calcium carbonate) cartridges: add calcium and alkalinity, easy to manage, steady taste. Good baseline option.
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Blends with magnesium media (dolomite or MgO): raise magnesium along with calcium; can increase pH more strongly. Balance contact time to avoid too much pH rise.
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Inline alkaline/mineral cartridges: often add calcium, magnesium, and trace minerals; simple drop-in approach.
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Liquid trace mineral drops: add by the glass or pitcher; gives control if you want more or less taste.
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Mixing: Some users blend a small amount of mineral water with RO water to achieve a target taste.
If you wonder, “What minerals are lost in reverse osmosis?” the main ones are calcium and magnesium, but RO also lowers sodium, potassium, sulfate, bicarbonate, and others. Remineralization focuses on calcium and magnesium because they control alkalinity, taste, and mouthfeel.
Choosing targets and verifying results
A practical target for home drinking water:
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Calcium: 20–40 mg/L
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Magnesium: 10–20 mg/L
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TDS: 80–150 mg/L
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Alkalinity: 40–100 mg/L as CaCO3
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pH: about 7.2–8.0
These numbers improve taste for most people and add buffering without creating heavy scale. You can check progress with a simple TDS meter and occasional water tests for hardness, alkalinity, and pH. Adjust media type, cartridge size, or flow rate to hit your preferred taste and mineral range.
Picking an approach (simple steps)
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If your goal is better taste with minimal effort: add a calcite post-filter.
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If you want more magnesium for mouthfeel: choose a calcite + magnesium blend.
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If you need fine control: use liquid trace mineral drops and measure TDS until you like the taste.
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If you have a coffee setup: aim for moderate alkalinity (50–70 mg/L as CaCO3) for flavor balance and machine protection.
RO Water Filtration System Design and Optimization Tips
Designing an RO system isn’t just about putting a membrane in a tank. Proper pretreatment, regular maintenance, and smart system layout all play a role in keeping the water safe, tasting good, and the system running efficiently. Let’s look at key tips for protecting the membrane, ensuring microbial safety, and optimizing performance while minimizing waste.
Pretreatment and membrane protection
Good pretreatment keeps an RO system healthy. Use a sediment filter with a micron rating that matches your water (for example, 5 microns for most municipal water, 1 micron if you see fine silt). Always include activated carbon before the RO membrane to remove chlorine and many organics. If your utility uses chloramine, use catalytic carbon and confirm the filter’s rated capacity. This prevents membrane damage and taste issues.
Microbial safety and storage
An RO membrane can block bacteria, but the storage tank and lines can still be a place where microbes grow if the system sits unused. If there’s any risk, add a UV light before the faucet. Also, sanitize the tank and lines on a schedule (for example, when you change filters) to keep the system clean. Check valves and flow restrictors help prevent backflow and keep concentrate from mixing with permeate.
Efficiency, recovery, and maintenance
Some users want to lower wastewater and improve production:
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A permeate pump or booster pump can raise pressure and improve recovery ratios, making more drinking water with less waste.
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Replace sediment and carbon filters on time. This protects the membrane and keeps taste fresh.
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Watch for “TDS creep” (a slow rise in permeate TDS). It can mean the membrane is aging or the carbon is due for replacement.
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Keep tubing runs tidy and avoid hot locations that can grow biofilm.
How often should I change RO water filters?
Use manufacturer guidance plus your water use and local water quality. A common schedule:
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Sediment filter: every 6–12 months
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Carbon prefilter(s): every 6–12 months
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RO membrane: every 1–2 years (earlier if high TDS or poor pretreatment)
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Remineralizer: every 6–18 months, depending on media and taste
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UV lamp (if used): yearly bulb change and sleeve cleaning
Interpreting Your Water Test
A basic lab test or utility report (Consumer Confidence Report) gives you a map. Focus on:
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Hardness (calcium and magnesium)
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Alkalinity and pH
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TDS
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Fluoride and nitrate
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Lead, arsenic, chromium (if relevant)
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Residual chlorine or chloramine
Then match system design to risks:
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If residual chlorine or chloramine is present: ensure strong carbon pretreatment
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If microbes are a concern: add UV after the RO tank
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If you want better taste and pH stability: add remineralization
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If you have PFAS concerns: use carbon + RO and request PFAS lab results
Key Takeaways and Next Steps
RO water provides very clean water and removes harmful contaminants effectively. However, it also reduces essential and beneficial minerals, which is why remineralization can help restore a balanced mineral profile for daily drinking.
Core conclusions (skim-friendly)
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RO water contains very low minerals. In short, the answer to “does RO water have minerals?” is “very few.”
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Yes, RO removes calcium and magnesium, which reduces scale but lowers mineral content in your drinking water.
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RO removes fluoride at meaningful levels (often around 90–95%). Check NSF/ANSI 58 listings for confirmation.
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RO membranes can block bacteria and many viruses, but UV or ultrafiltration is wise for consistent microbiological assurance.
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The RO membrane does not remove chlorine well; activated carbon prefilters handle chlorine and protect the membrane.
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Remineralization restores taste, raises alkalinity, and can support a more balanced mineral profile.
Action plan
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Test your water or review your utility’s report.
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Choose an RO system with strong sediment and carbon pretreatment (catalytic carbon if you have chloramine).
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Decide if you want RO system remineralization for taste and alkalinity. Pick calcite or calcite + magnesium to start.
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If microbes are a concern, add a UV stage after the tank.
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Set filter change reminders and monitor TDS. Replace the membrane when TDS rises or production drops.
Is remineralized RO water better than bottled mineral water?
It depends on your goals. Remineralized RO lets you target taste and alkalinity in your home, with less plastic waste and lower long-term cost. Bottled water that contains beneficial minerals has a stable natural profile that some people prefer. If you want control and consistency, remineralized RO is hard to beat. If you love a specific spring mineral profile, bottled can be a treat. Many people do both: remineralized RO at home and bottled when traveling.
FAQs
1. Does reverse osmosis filter out calcium?
Yes, it does. Reverse osmosis is really good at removing most of the calcium from water. That’s one reason why RO water tends to be “soft”—it helps reduce scale buildup in your pipes, coffee maker, and kettle. Basically, if you’ve had trouble with hard water leaving spots or mineral deposits, an RO system can make a noticeable difference.
2. What cannot be removed by reverse osmosis?
Well, RO membranes are amazing at filtering out dissolved solids, but they’re not perfect for everything. For example, free chlorine and chloramine don’t get filtered out efficiently just by the RO membrane. That’s why most systems include an activated carbon pre-filter—it handles those chemicals before the water hits the RO membrane. Also, some dissolved gases, like carbon dioxide (CO₂), can sneak through, so RO isn’t a magic fix for every impurity.
3. Will reverse osmosis remove bacteria?
An RO membrane can reject bacteria and many viruses if it’s intact, which is great for general water safety. But just to be extra safe, especially if your water source might be contaminated, it’s smart to pair your RO system with UV sterilization or an ultrafiltration stage. That combination gives you a higher level of microbial protection, so you’re not leaving anything to chance.
4. Does a reverse osmosis system remove fluoride?
Yes, it does a pretty good job. Typical RO systems can cut fluoride levels by about 90–95%. If fluoride is something you’re concerned about—either wanting to reduce it or make sure it meets safety standards—look for systems that are certified under NSF/ANSI 58 for fluoride reduction. That certification gives you confidence that the RO is performing as advertised.
5. Do I need to add minerals to reverse osmosis water?
That’s totally optional. RO water can taste a bit “flat” because it’s stripped of minerals like calcium and magnesium. Many people like to add minerals back in—not just for taste, but also to stabilize pH and create a more balanced water profile. A simple way is to use a calcite stage, or a combination of calcite and magnesium, which gently remineralizes the water without complicating your system.
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