Do you need to add minerals back to reverse osmosis (RO) water from a desalination watermaker?
This is one of the most common questions we receive from boat owners and watermaker users.
The short answer is: for most people, probably not.
While adding minerals back to purified water is unlikely to cause harm, there is little evidence that healthy people need to remineralise water produced by a modern reverse osmosis desalination system. Most of the minerals your body requires come from food, not drinking water.
At Rainman, we are not dieticians or medical professionals, so you should seek your own medical advice. After years of working with desalination systems and reviewing the available research, here is our perspective.
1. Most Minerals Come From Food, Not Water
While drinking water can contribute small amounts of calcium and magnesium in some locations, nutrition experts consistently emphasise dietary sources as the primary means of meeting daily requirements. A healthy diet is the primary source of essential minerals such as calcium, magnesium, potassium, zinc, and iron.
For example:
- A serving of leafy greens contains more magnesium than several litres of mineralised water.
- Dairy products, nuts, seeds, legumes, fish, and vegetables provide substantial amounts of essential minerals.
- Drinking water generally contributes only a small percentage of daily mineral intake for most people.
If you are eating a balanced diet, your nutritional needs are typically met through food rather than water.
2. Millions of People Drink Low-Mineral RO Water Every Day
Reverse osmosis systems are widely used in homes, businesses, and municipal water treatment facilities around the world.
Typical total dissolved solids (TDS) levels are:
| Water Source | Typical TDS |
|---|---|
| Distilled Water | ~10 ppm |
| Domestic RO Water | ~25 ppm |
| Rainman Watermaker Water | ~150–500 ppm |
| Municipal Desalination Water | ~200–600 ppm |
| Many Bottled Waters | ~500 ppm |
While domestic RO systems often produce very low-TDS water, Rainman watermakers typically produce water in the same broad range as municipal desalination plants and many bottled waters demonstrating that drinking water is safely consumed across a very wide range of mineral concentrations.
3. Desalinated Water Around the World Is Consumed Safely
Many regions rely heavily on desalinated water for drinking supplies.
Countries and regions including parts of the Middle East, Australia, Spain, and the United States use desalination as a major source of potable water.
In many municipal systems, minerals are added back primarily for:
- Corrosion control
- Distribution network protection
- Taste improvement
- Regulatory compliance
Human nutrition is not always the primary reason for remineralisation.
4. Taste Is Often the Main Difference
Some people prefer the taste of mineral-rich water.
Others enjoy the clean, neutral taste of purified RO water.
Taste preferences vary considerably between individuals, and adding minerals can alter flavour without necessarily providing a significant nutritional benefit.
For many boat owners using a watermaker, the convenience of producing clean drinking water outweighs any desire to adjust its mineral content.
5. Remineralisation Adds Complexity
Adding minerals back into water means introducing additional equipment, consumables, maintenance, and cost.
Depending on the method used, this may involve:
- Mineral cartridges
- Dosing systems
- Additional filters
- Replacement filter media
For many cruising sailors and remote travellers, simplicity and reliability are important advantages. Drinking water directly from a properly maintained watermaker avoids adding unnecessary complexity.
Exceptions: When Mineral Intake May Matter More
Survival Situations or Severe Food Shortages
One scenario where mineral content may become more important is a survival situation.
If a person is consuming very little food for an extended period, water could become a more significant source of minerals. In those circumstances, nutritional planning becomes more complex and should be guided by medical or nutritional expertise.
However, this is very different from normal cruising, boating, RV travel, or everyday use of a desalination system.
Medical Considerations
If you have unique medical conditions, such as pregnancy, GI disorders, kidney conditions, etc., always consult your physician for advice.
Our View
At Rainman, our view is simple:
It doesn’t hurt to remineralise water, but for most healthy people it is probably unnecessary.
If you enjoy the taste of mineralised water, adding minerals back may improve your drinking experience. However, if you are eating a normal, balanced diet, there is little reason to believe that watermaker water alone will create a mineral deficiency.
The vast majority of the minerals your body needs come from food, not from drinking water.
For most Rainman owners, producing clean, safe drinking water directly from the watermaker is all that is required.
References and Further Reading
World Health Organisation – Calcium and Magnesium in Drinking Water
Frontiers in Nutrition Article