What Does TDS Mean in Water? | TDS Levels & Removal Methods Explained

Total Dissolved Solids (TDS) is one of the most commonly referenced terms in water treatment. Whether you're managing an industrial facility, maintaining a reverse osmosis (RO) system, or evaluating your water quality, understanding what TDS means is essential.

In this article, we'll explore the definition of TDS, its impact on water quality and equipment, acceptable levels for different applications, and how advanced technologies like RO systems can help reduce TDS effectively.

If you've ever asked, "What does TDS mean?" or "Is high TDS in water bad?"—this guide is for you.

What Is TDS in Water?

TDS stands for Total Dissolved Solids, which refers to the total concentration of dissolved substances in water. These solids include inorganic salts such as calcium (Ca²⁺), magnesium (Mg²⁺), sodium (Na⁺), chloride (Cl⁻), sulfate (SO₄²⁻), and bicarbonate (HCO₃⁻), as well as trace amounts of organic compounds.

Unlike suspended particles, TDS cannot be removed by simple filtration. The solids are completely dissolved and require more advanced treatment methods—such as reverse osmosis (RO)—to be effectively reduced.

TDS is commonly measured in parts per million (ppm) or milligrams per liter (mg/L). While some amount of dissolved solids is normal, excessively high levels can negatively affect water taste, safety, and equipment performance.

Why Does TDS Matter in Water Treatment?

Total Dissolved Solids (TDS) is more than just a water quality indicator—it's a key factor that directly affects the performance, longevity, and efficiency of water treatment systems.

Here are several reasons why monitoring and managing TDS is critical in industrial and commercial settings:

• Equipment Protection: High TDS levels can lead to scale formation on reverse osmosis (RO) membranes, boilers, heat exchangers, and pipelines, reducing efficiency and increasing maintenance costs.
• Water Quality and Taste: For drinking or food processing, elevated TDS levels can negatively affect taste and appearance, especially when involving chloride, sulfate, or iron.
• Regulatory Compliance: Many industries must meet specific discharge or process water standards, including maximum TDS limits.
• Process Stability: Certain manufacturing operations, such as electronics or pharmaceuticals, require water with extremely low TDS to avoid contamination or process variability.

In short, managing TDS is not just about improving water—it’s about protecting your process, your equipment, and your bottom line.

How Is TDS Measured?

Measuring TDS is a straightforward but essential step in water quality monitoring. The most common methods include:

• TDS Meter (Conductivity Method): This handheld or inline device estimates TDS by measuring the electrical conductivity (EC) of water and applying a conversion factor. It's quick, practical, and widely used in field testing.
• Gravimetric Method: A laboratory-based method where water is evaporated and the remaining residue is weighed. This provides the most accurate result but is time-consuming and not practical for routine monitoring.
• Laboratory Analysis: Professional water analysis services can provide a detailed breakdown of individual ions contributing to TDS, such as calcium, magnesium, sodium, and chlorides.

TDS is usually reported in milligrams per liter (mg/L) or parts per million (ppm). For example, a reading of 500 ppm means that there are 500 milligrams of dissolved solids in one liter of water.

Note: In most industrial applications, TDS meters are sufficient for daily operation, but lab analysis is recommended for system design and troubleshooting.

What Is a Good TDS Level in Water?

The ideal Total Dissolved Solids (TDS) level varies depending on the intended use of the water. While some dissolved minerals are beneficial or harmless, excessive concentrations can reduce performance and safety in industrial, agricultural, and domestic applications.

Water with TDS above 2,000 ppm may require special treatment methods, especially in industries such as electronics, pharmaceuticals, and food processing. If you're unsure about the TDS threshold for your application, consult a water treatment expert.

How to Reduce TDS in Water Effectively?

High TDS levels in water can negatively impact equipment, processes, and end-product quality. To ensure water quality meets your specific application requirements, choosing the right treatment method is essential. Below are the most common and effective technologies used to reduce TDS:

• Reverse Osmosis (RO): RO is the most effective method for removing TDS. It works by forcing water through a semi-permeable membrane, leaving behind dissolved salts and other impurities. RO systems can reduce up to 99% of TDS, making them ideal for industrial and commercial use. Explore STARK RO systems.
• Distillation: This method involves heating water to create steam and then condensing it, leaving most dissolved solids behind. While effective, it’s energy-intensive and typically reserved for lab or high-purity needs.
• Deionization (DI) / Ion Exchange: Suitable for polishing RO water or low-TDS feedwater, DI systems remove ions through chemical resins. Often used in electronics, pharmaceuticals, and ultrapure water applications.
• Electrodeionization (EDI): Combines ion exchange and electricity to remove residual TDS after RO. Common in ultrapure water systems. Learn how EDI works here.

Among these options, reverse osmosis is the most scalable and cost-effective for general TDS reduction in industrial applications.

STARK RO Systems for TDS Control

At STARK Water, we specialize in designing and manufacturing high-performance reverse osmosis systems tailored to meet diverse industrial needs across the globe—including regions with high TDS feedwater, such as the Middle East and coastal areas.

Our RO systems feature:

• High-rejection membranes for consistent TDS reduction up to 99%
• Modular design to suit flow rates from 500 to 100,000 liters per hour
• Stainless steel and FRP construction options to fit chemical and environmental requirements
• Pre-treatment integration (media filters, softeners, antiscalant dosing) for long-term membrane protection
• Remote monitoring and automation for efficient operation

We also provide replacement membranes, cleaning chemicals, and custom RO solutions to help you manage your TDS challenges with confidence.

Conclusion

Understanding what TDS means—and how it impacts your water system—is the first step toward optimizing water quality and protecting your infrastructure.

Whether you're dealing with hard well water, seawater desalination, or industrial wastewater reuse, managing TDS effectively ensures longer equipment life, better process stability, and compliance with water quality standards.

Reverse osmosis remains the most effective and scalable solution for reducing TDS, and STARK Water is here to help you choose, implement, and maintain the right system for your needs.

Contact our water treatment experts to discuss your water quality goals, or browse our industrial RO systems today.