Water is the essence of life. Whether it’s for drinking, cooking, or daily hygiene, having clean and safe water is a fundamental necessity. In many parts of the world, including India, water purification using Reverse Osmosis (RO) has become very popular. If you’re considering an RO system or already use one, you might have heard of the term TDS — Total Dissolved Solids. You may wonder: What is the ideal TDS level recommended for RO water purification? This blog post will explore that question in depth.
Understanding TDS: What Exactly Are Total Dissolved Solids?
TDS, or Total Dissolved Solids, refers to all the inorganic and some organic substances dissolved in water. These solids are usually minerals, salts, metals, and ions naturally present in water. Common components of TDS include calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulfates.
The concentration of these dissolved solids is usually measured in parts per million (ppm) or milligrams per liter (mg/L). For practical purposes, ppm and mg/L can be considered interchangeable.
Why does TDS matter? Because it affects the water's taste, safety, and suitability for consumption.
Why Is TDS Important for Drinking Water?
TDS influences several aspects of water quality:
1. Taste and Palatability
Water with very low TDS often tastes flat or bland. Minerals dissolved in water give it a characteristic taste that we associate with fresh, clean water. Conversely, water with excessively high TDS may taste salty, bitter, or metallic, which is unpleasant.
2. Health and Nutrition
Some dissolved minerals like calcium and magnesium contribute to your daily nutritional needs. Although food remains the primary source of these minerals, water can add to your intake. Drinking water with extremely low TDS means you are missing out on these potentially beneficial minerals.
3. Safety Concerns
High TDS levels can sometimes indicate the presence of harmful contaminants, such as heavy metals or salts. However, TDS itself is not a definitive measure of safety because it does not indicate which specific substances are dissolved, only their total concentration.
4. Impact on Appliances and Plumbing
High levels of dissolved solids lead to hard water, causing scaling and deposits in water heaters, kettles, pipes, and RO membranes, reducing their lifespan and efficiency.
What Are the Recommended TDS Levels for Drinking Water?
National and international agencies provide guidelines on acceptable TDS levels in drinking water to balance health and taste considerations.
In India, the Bureau of Indian Standards (BIS) specifies that the maximum permissible TDS level in drinking water is 500 mg/L (or 500 ppm). However, the preferred or ideal levels are often much lower for better taste and health.
Globally, many experts suggest that water with TDS below 300 ppm is generally good for drinking.
What is the Ideal TDS Level for RO Water?
Since RO systems purify water by removing dissolved solids, it’s essential to know the target TDS range for safe and palatable drinking water after purification.
Here’s a practical breakdown:
|
TDS Level (ppm) |
Implications (Water Quality Impact) |
|
Less than 50 ppm |
Water is very pure but tastes flat and lacks minerals. Not Ideal for long term consumption |
|
50 to 150 ppm |
Ideal range for RO Water; balance purity and mineral content with good taste. |
|
150 to 300 ppm |
Acceptable and Safe; Water has more minerals, taste is good but higher TDS may indicate hardness. |
|
Above 300 ppm |
Water may taste salty or unpleasant and can indicate the presence of excessive dissolved solids. |
|
Above 500 ppm |
Exceeds the maximum permissible limits, potentially unsafe and not recommended. |
Most water purifiers aim to bring the TDS down to the 50 to 150 ppm range, ensuring water is safe, tastes good, and contains essential minerals.
Why Not Zero TDS Water?
You might wonder, if RO removes almost all dissolved solids, why not have the purest water possible with nearly zero TDS? Here are a few reasons why zero TDS water isn’t always the best:
- Taste: Water with no dissolved minerals tastes flat and lacks the fresh quality many prefer.
- Health: Minerals like calcium and magnesium are essential for the body. Drinking water can be a source of these minerals.
- Corrosiveness: Very pure water can be slightly corrosive, potentially causing leaching of metals from pipes or containers.
Because of these reasons, many modern RO purifiers include a mineralizer or TDS controller, which adds back essential minerals to the purified water to bring the TDS up to a desirable level.
How Do RO Purifiers Control TDS?
RO purification involves passing water through a semi-permeable membrane that blocks dissolved solids, effectively reducing TDS.
- Raw Water TDS: The TDS of source water varies greatly depending on location and source — it could be as low as 100 ppm or as high as 2000 ppm or more.
- Post-RO TDS: RO membranes typically reduce TDS by 90-99%. If the source water has 1000 ppm TDS, the output might be as low as 10-50 ppm.
- TDS Controller: To prevent the water from having too low TDS, many RO systems mix a controlled amount of untreated water back into the purified water. This ensures better taste and mineral content.
- Mineral Cartridges: Some systems add calcium or magnesium minerals to boost TDS and improve water taste.
For example, Kent RO purifiers, one of the most popular brands in India, use a combination of RO, UV, and UF purification along with a TDS controller and mineral RO technology. This setup not only purifies the water by removing harmful substances but also retains essential minerals, ensuring that the output water maintains a TDS level that's both safe and healthy for drinking.
What Happens If TDS is Too High or Too Low in RO Water?
If TDS is Too High:
- The water may still contain high amounts of dissolved salts or contaminants, reducing safety.
- The taste may be unpleasant (salty, bitter).
- Increased risk of health issues due to excessive mineral or contaminant intake.
- Appliances and pipes may develop scale deposits.
If TDS is Too Low:
- Water tastes flat or bland.
- Lack of essential minerals that aid health.
- Possible corrosive nature affecting pipes or containers.
- Some consumers may reject such water due to taste and perceived “emptiness.”
Practical Recommendations for RO Users
- Check your source water TDS: Knowing the TDS of your input water helps determine if you need RO and what settings to use.
- Aim for post-RO TDS of 50 to 150 ppm: This range balances safety, taste, and mineral content for most people.
- Use TDS controllers or mineral cartridges: These features are vital for adjusting TDS to a desirable level after purification.
- Maintain your RO system: Regular replacement of membranes and filters ensures effective TDS reduction.
- Monitor TDS regularly: Using a TDS meter at home is an easy way to keep track of water quality.
- Don’t over-purify: If your water source has low TDS (below 300 ppm), you might not need an RO purifier, or you can use UV or UF filters instead to avoid unnecessarily stripping beneficial minerals.
Conclusion: What Should You Take Away About TDS Levels and RO Water?
Understanding TDS and its recommended levels in RO water is crucial for ensuring safe, tasty, and healthful drinking water.
- Total Dissolved Solids represent the concentration of minerals and salts in water.
- RO purifiers reduce TDS significantly, improving water safety but potentially affecting taste and mineral content.
- The ideal TDS level for RO-purified drinking water generally lies between 50 and 150 ppm.
- Water with TDS below 50 ppm lacks minerals and taste; water above 300 ppm may taste unpleasant or be unsafe.
- Modern RO systems incorporate methods to restore minerals and control TDS levels post-purification.
- Regular testing and maintenance help ensure your RO system works efficiently and water quality remains optimal.
If you want the best drinking experience and health benefits, aim for that balanced TDS range. And remember — TDS is one of many water quality parameters. Always consider microbial contamination, chemical pollutants, and source water safety along with TDS for the complete picture.