TDS controllers are an essential part of the water purification process in a contemporary Indian home. Total Dissolved Solids (TDS) controllers play an important role, as the TDS controller addresses the critical issue of balancing the purity of water with the mineral content. In the increasingly common method of purifying water (i.e., via reverse osmosis, or RO), understanding what TDS controllers do and how to use them effectively is essential.
This article offers an in-depth analysis of TDS controllers (including defining what they are, describing how they work, and discussing their benefits) and why using a TDS controller is simply a better option for maintaining optimal TDS levels in drinking water.
What is TDS and Why Does It Matter?
To understand what a TDS controller does, it is necessary to know what TDS is. TDS is the total amount of dissolved solids in water. These dissolved solids include salts with a small amount of organic matter. Cations (calcium, magnesium, potassium, and sodium) are usually the primary component along with anions (carbonates, nitrates, bicarbonates, chlorides, and sulfates).
The Bureau of Indian Standards (BIS) regulates TDS in potable water and provides the maximum permissible limit. The maximum permissible limit for potable water TDS is 50 mg/L to 500 mg/L. TDS levels below the minimum level have very little flavor and usually have a lack of minerals that are essential for the human body.
Conversely, TDS levels above the maximum limit usually make water taste either salty or bitter, and consuming this type of water for a prolonged period of time could create health problems. Having balanced levels of TDS in water is very important for taste purposes as well as for health benefits.
The Role of Reverse Osmosis (RO) and Its Limitation
Reverse osmosis (RO) is an extremely efficient water purification process. In this process, a semi-permeable membrane is used to filter a variety of contaminants from water, including hardened metals, dissolved salts, microscopic organisms (bacteria, viruses, etc.), and many other impurities. An RO membrane has tiny pore openings of approximately 0.0001 microns in size, allowing water molecules to pass through while blocking the passage of much larger contaminants.
While an RO system does an excellent job of producing safe drinking water, there is one major drawback to this purification process: it is non-selective in nature. This means that RO systems also remove virtually all of the dissolved substances from the water (including beneficial minerals such as calcium and magnesium).
This results in RO water TDS levels dropping to extremely low levels (often below 20 mg/liter). Consuming demineralized water is not desirable for our bodies to function properly. It is in this situation that the use of a TDS controller in water purifiers becomes essential.
What is a TDS Controller in a Water Purifier?
A TDS controller (Total Dissolved Solids) can be a device or feature of a purifier that is used to regulate the TDS level of purified water. It is a TDS control by the simplest and most effective measure to ensure that you get clean, excellent, and safe-to-drink water.
Essentially the TDS controller is a manual or automatic valve that allows a very small amount (controlled) of the raw or untreated water to bypass the RO membrane. The water not being treated bypassing this portion still contains its own natural minerals and will be mixed with the fully purified RO water (after it has passed through the RO filter). Mixing this portion of water with the fully purified RO water will raise the TDS level of the total output water, thereby restoring some of the essential minerals that were removed by the RO purification process.
Water purifiers with a TDS controller are usually marketed as mineral RO purifiers because they help to preserve natural minerals, giving you a preferred and healthier way to drink water.
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How Does a TDS Controller Work?
The operation of a TDS controller is simple and ingenious and can be understood with the following step-by-step breakdown of how it works:
Water Splitting: When the input water enters the purifier, it is split into two streams.
RO Purification: Most of the water is directed into the normal reverse osmosis (RO) purification process, where it has had all impurities and dissolved solids removed, resulting in a low TDS level .
Bypass Channel: A small amount of the input water is sent through a separate bypass channel that has not gone through the RO membrane and therefore retains its overall TDS and mineral content.
Mixing Chamber: The ultra-pure RO water and the mineral-rich bypass water will then be mixed in a controlled ratio in a mixing chamber.
Final Output: The resulting mixture will have a TDS level greater than that of the pure RO water but less than that of the input water. This controlled blending of water ensures that the final output water has been balanced for taste and safety with the correct levels of essential minerals.
In many advanced models, adjustment of TDS levels to specific desired values is done. Based on the level of contamination in input water and individual user preferences for the TDS in output water, users can set their desired TDS levels.
TDS Controller vs. Mineral Add-on Cartridge
It is crucial not to confuse a TDS controller with a mineral add-on or alkaline cartridge. While both aim to enhance the mineral content of RO water, they operate on different principles.
| Feature | TDS Controller | Mineral Add-on / Alkaline Cartridge |
| Mechanism | Blends a small amount of raw water with purified RO water. | Artificially adds specific minerals to fully purified RO water. |
| Source of Minerals | Retains some of the natural minerals from the source water. | Adds artificial minerals (like calcium and magnesium balls) from the cartridge. |
| Control | The final TDS level depends on the input water’s TDS. | Provides a more consistent TDS level, independent of input water. |
| Contaminant Risk | If input water has harmful contaminants, a small amount may pass through. | Only purified water passes through, ensuring no contaminants are added. |
| Taste | Improves taste by restoring natural mineral balance. | Can significantly alter the taste, sometimes making it sweeter or slightly bitter. |
| Cost | Generally a more cost-effective solution. | Cartridges need periodic replacement, adding to the maintenance cost. |
When the input water has a moderately high TDS level but is not overly contaminated, a TDS controller is the best option. For places with very high TDS or known contamination, a mineral add-on is better because it makes sure that only purified water is mineralized.
Benefits of a Water Purifier with TDS Controller
Investing in the best water purifier with a TDS controller offers numerous advantages:
Retains Essential Minerals: The most important benefit of using a water purifier with TDS control is that it will help you retain important minerals such as calcium, potassium and magnesium, which play critical roles in the health of your bones, metabolism and overall health.
Enhances Taste: Water that is balanced with TDS has a much better taste than totally demineralized water, making drinking it more enjoyable.
Provides Health Benefits: Consuming mineral enriched water is a way to meet your daily nutritional requirement for minerals, which are also necessary for the smooth functioning of many of your body functions.
Cost-Effective: A TDS controller is a cost effective method of mineral replacement, especially when considering that you are using a cartridge that requires regular replacement.
Adjustable TDS: Many new and improved water purifiers have an RO purification system that lets you adjust the TDS level of your water, allowing you to customize the level of mineral content.
Related: 14 Best Water Purifiers in India | Ultimate Buying Guide and Reviews
Is a TDS Controller Necessary?
If water TDS is between 200-500 ppm: If the TDS of the water that you are going to be using in your water purifier is in this range, we highly recommend a TDS controller.
If water TDS is very high (above 1000 ppm): A standard reverse osmosis (RO) unit is a must for this type of water; however, a TDS controller can be used as well. We recommend that you consider using a mineralizing accessory with a TDS controller to ensure that the final product is pure and mineralized.
If water TDS is very low (less than 200 ppm): You might not require an RO system at all. If you do, a TDS controller is essential to keep the TDS level from falling too low.
We always recommend that you have your water tested to obtain information about the TDS and the various contaminants that are present in your water supply prior to purchase.
Conclusions
Purified water doesn’t mean sacrificing valuable nutrients. The TDS controllers in water purifiers offer an ideal combination of leading-edge purification and nutrition technology by eliminating contaminants while adding back essential minerals your body needs.