Reverse osmosis strips out 94-98% of the calcium and magnesium in your water, along with virtually every other dissolved mineral. That leaves you with extremely pure water, but also water that tastes flat, runs slightly acidic (pH 5.0-6.5), and no longer contributes minerals to your diet. Remineralizing it is straightforward, and you have several options depending on your budget and how hands-on you want to be.
Why RO Water Needs Minerals Added Back
The concern isn’t just taste. Water with very low mineral content actually leaches minerals from food during cooking, with losses reaching up to 60% for calcium and magnesium and even higher for trace elements like copper and manganese. Over time, regularly drinking and cooking with demineralized water may contribute to lower bone density, and an expert consensus group convened by the WHO concluded that the link between harder water and reduced cardiovascular disease risk is probably valid, with magnesium as the likely driver of that benefit.
A good remineralization target is a total dissolved solids (TDS) reading between 50 and 150 ppm. That range provides enough calcium, magnesium, and trace minerals to taste clean and pleasant without the flat flavor of pure RO water, while also contributing meaningfully to your daily mineral intake. You’re not trying to make mineral water. You’re trying to bring the water back to something close to what a natural spring would produce.
Inline Remineralization Filters
The most common approach is adding a remineralization cartridge directly to your RO system as a final stage. These filters contain mineral media that dissolve slowly as water passes through them. The two main types of media are calcite, which is natural calcium carbonate, and a magnesium oxide product. Calcite raises pH gently and adds calcium. Magnesium oxide is far more reactive, neutralizing about five times more acidity per unit of weight than calcite, and it adds magnesium to the water in the process.
Many remineralization cartridges blend both media together so the output water contains a balance of calcium and magnesium rather than just one. A typical system with a remineralization stage produces water in the pH 7.0-8.5 range, compared to the 5.0-6.5 you’d get from RO alone. These cartridges need replacement every 6 to 12 months, since the mineral media gradually dissolves and becomes depleted. Replacement cartridges are widely available for most under-sink and countertop RO systems.
If your RO system didn’t come with a remineralization stage, you can usually add one. Most systems use standard-sized filter housings, and aftermarket remineralization cartridges are designed to fit inline after the RO membrane and storage tank.
Liquid Mineral Drops
Concentrated trace mineral drops are the simplest option if you don’t want to modify your plumbing. The most widely available product, ConcenTrace, is harvested from the Great Salt Lake and contains over 72 trace minerals. A half-teaspoon serving provides 250 mg of magnesium along with smaller amounts of potassium, sulfate, lithium, boron, and calcium.
For remineralizing a full gallon of RO water, 20 to 40 drops is the recommended range. For a single glass, 2 to 4 drops does the job. Start at the lower end and adjust based on taste. Too many drops and the water picks up a slightly salty or mineral flavor. The drops are concentrated enough that a single bottle lasts months, making this one of the more economical approaches for small households or anyone who fills water bottles on the go.
Mineral Stones
Ceramic mineral balls or natural mineral stones (sometimes sold as maifan stone) sit in a pitcher or dispenser and slowly release minerals into the water over hours. Maifan stone is a natural ore containing calcium, magnesium, potassium, sodium, silicon, manganese, and other trace elements. It also has a natural pH-buffering effect, nudging acidic water toward neutral.
The trade-off is speed and consistency. Mineral stones work passively, so the mineral content of your water depends on how long the water sits in contact with the stones and how depleted the stones have become. You won’t get the same precision as an inline filter or measured drops. Stones typically need replacing every few months, and they should be rinsed periodically to prevent biofilm buildup. This method works best for people who fill a pitcher and let it sit for several hours before drinking.
DIY Salt and Baking Soda Method
A simple kitchen approach uses Himalayan pink salt and baking soda. A common ratio is 1/8 teaspoon of Himalayan pink salt plus 1/4 teaspoon of baking soda per liter of water, stirred until fully dissolved. The salt contributes trace minerals (Himalayan salt contains small amounts of calcium, magnesium, potassium, and iron alongside sodium chloride), while the baking soda raises pH.
This method is inexpensive and requires nothing beyond ingredients you may already have. The downside is that it adds more sodium than other methods, which matters if you’re watching your sodium intake. It also requires manual mixing every time, making it less convenient than a filter or drops. If you go this route, consider reducing the baking soda slightly and tasting as you go, since a quarter teaspoon per liter can make the water taste noticeably alkaline to some people.
Comparing the Methods
- Inline remineralization filter: Best for households using an under-sink or countertop RO system. Fully automatic, consistent mineral output, requires filter changes every 6-12 months. The most set-it-and-forget-it option.
- Liquid mineral drops: Best for flexibility and portability. Easy to dose precisely, lasts a long time per bottle, works with any water container. Adds a broad spectrum of trace minerals.
- Mineral stones: Best for pitcher-based setups. No ongoing cost beyond occasional stone replacement. Less precise and slower acting.
- DIY salt and baking soda: Best for cost-conscious users who don’t mind mixing each batch. Adds more sodium than other methods.
How to Check Your Results
A TDS meter is the easiest way to verify that your remineralization is working. These handheld devices cost under $15 and give you an instant reading in parts per million. Straight RO water typically reads between 10 and 30 ppm. After remineralization, you’re aiming for that 50-150 ppm sweet spot. If you’re using drops or the DIY method, a TDS meter lets you dial in the exact amount to add rather than guessing.
A pH test strip or digital pH meter can confirm you’ve brought the water out of the acidic range. Anything between 7.0 and 8.5 is a reasonable target. If your water still reads below 7.0 after remineralization, you likely need to increase the mineral content slightly or, if you’re using an inline filter, check whether the cartridge is due for replacement.