How to Reduce TDS in Water?

Water is an essential resource in our daily lives, but sometimes our tap water can contain too much total dissolved solids (TDS) such as minerals and salts, resulting in less than optimal water quality. In this article, we will look at ways to reduce TDS in our water to ensure we enjoy clear and healthy water.

What is TDS?

TDS stands for “Total Dissolved Solids”, which translates to “Total Dissolved Solids” and refers to the sum of all solids dissolved in water, which can include minerals, salts, metal ions, inorganic substances, organic substances, etc. TDS is usually expressed in milligrams per liter (mg/L) or as a fraction. These dissolved solids can include minerals, salts, metal ions, inorganic and organic substances, etc. TDS is usually expressed in milligrams per liter (mg/L) or as a percentage to indicate the amount of dissolved substances in the water.

The measurement of TDS is an important indicator of water quality because high TDS water may have an effect on the taste, appearance and suitability of the water. Some water sources naturally contain high levels of TDS, while in other cases, high TDS water may result from an excess of salts, minerals or other dissolved substances in the water. In some applications, such as drinking water or industrial processes, the TDS in the water needs to be reduced to meet specific water quality requirements.

Methods to Reduce TDS

Reverse Osmosis (RO)

Reverse osmosis is a highly efficient method of removing most of the TDS from water by filtration through a semi-permeable membrane.This is a common method used for domestic water purification and industrial applications.RO systems are effective in removing salts, minerals, and other dissolved solids.

Reverse osmosis (RO) is a more convenient and widely used method due to the following advantages of RO systems:

• Efficiency: Reverse osmosis systems are highly efficient at removing most dissolved solids, salts, and minerals from water, making it clear and reducing TDS.
• Easy to install and use: Domestic RO systems are relatively easy to install and can be placed under the kitchen faucet to provide direct access to drinking water. Such systems are usually easy to operate.
• Scalable: RO systems can be scaled up as needed to handle larger volumes of water for different sized applications.

Distillation

Distillation is the process of reducing TDS by heating water to the boiling point and then collecting the vapors and condensing them into pure water.

Deionization (DI)

Deionization is a method of removing ions from water using ion exchange resins to reduce TDS.

Ion Exchange

Ion exchange systems reduce TDS by replacing unwanted ions with more acceptable ones.

Electrodialysis

Electrodialysis uses an electric field to push ions through a selectively permeable membrane, which separates them from the water and reduces TDS.

Chemical Treatment

Chemical methods include coagulation and flocculation, where chemicals are added to cause dissolved substances to coalesce into small solid particles, which can then be removed from the water by filtration or precipitation.

Dilution

Dilution is the reduction of TDS by mixing high TDS water with low TDS water. This method can reduce the concentration of TDS water in some cases, but is not suitable for large scale applications.

Method	TDS Reduction	Cost	Maintenance	Best For	Notes
Reverse Osmosis (RO)	High	Medium	Medium	Drinking water, home water purification, pre-treatment	The most common and practical option for most households and drinking water applications.
Deionization (DI)	Very high	Medium to high	High	Laboratories, electronics, ultra-low ionic water needs	Suitable when extremely low TDS is required, but resins need regular replacement.
Distillation	Very high	High	Low to medium	Small-volume purified water needs	Removes a large amount of dissolved solids, but energy use is relatively high.
Ion Exchange	Medium to high	Medium	Medium	Water softening, specific industrial treatment	More effective for certain ions and may not replace RO in all cases.
Electrodialysis	Medium to high	High	Medium	Industrial water treatment, continuous systems	Common in professional applications, but the system is more complex.
Dilution / Mixing	Low to medium	Low	Low	Aquariums, gardening, temporary adjustment	This does not remove TDS; it only lowers concentration by mixing with lower-TDS water.

How Should I Choose for Different Situations?

Drinking Water
For household drinking water, Reverse Osmosis (RO) is the top choice. It balances effectiveness, cost, and ease of use to reduce TDS reliably for daily consumption.

Laboratories & Precision Applications
Choose Deionization (DI) or Distillation for labs, sensor calibration, or electronics manufacturing. These deliver ultra-low ionic levels with verifiable stability.

Aquariums & Planted Tanks
Opt for RO followed by remineralization or dilution with tap water. This controls TDS while preserving essential minerals for fish and plants.

Coffee & Tea Brewing
Use RO with controlled remineralization. Low TDS improves flavor extraction without stripping necessary minerals that affect taste.

Industrial & Continuous Production
Electrodialysis or RO + Ion Exchange combos suit factories. They prioritize flow rate, scalability, and long-term operating costs.

How Do I Monitor TDS?

To monitor total dissolved solids (TDS) in water, you can use a TDS instrument or a measuring instrument, such as the A30 Digital TDS EC Meter.These tools, often referred to as TDS meters or TDS gauges, measure the amount of TDS in a water sample to determine the level of dissolved substances in the water. Below are the general steps to monitor TDS:

1. Obtaining a water sample: First, you need to obtain a sample of the water you wish to measure TDS in. This can be tap water, well water, river water, lake water, or any other source of water you are interested in. Make sure that the sample is fully representative.
2. Prepare the TDS instrument: If you have a TDS instrument, make sure it is calibrated and in good working order. Calibration usually requires the use of a standard buffer (usually a 1000 ppm standard) to ensure accurate measurements.
3. Measuring TDS: Insert the electrode or probe of the TDS instrument into the water sample. Make sure that the electrode does not touch the bottom or side walls of the container to avoid being affected by impurities. Wait for a while until the measurement stabilizes and then record the reading. Typically, TDS is expressed in milligrams per liter (mg/L) or as a partial percentage (%).
4. Cleaning and storage: Always clean the electrodes or probes after using the TDS instrument to avoid cross-contamination. Store the TDS instrument properly according to the manufacturer’s recommendations to ensure long-term performance.

Impact Of TDS On Water Quality

TDS is the sum of dissolved substances in water, including minerals, salts, metal ions, inorganic and organic substances. It affects water quality in many ways, and the following are some of the important effects of TDS on water quality:

• Taste and odor: High TDS water often has an unusual taste and odor, which may include salty, bitter, metallic, or other off-flavors. This not only affects the taste of drinking water, but may also affect the flavor of food and beverages.
• Appearance: High TDS water usually causes the water to become cloudy or colored, which may affect the appearance of the water and make it unsuitable for drinking or use in cooking.
• Scale and sediment: Dissolved substances in high TDS water can lead to deposits of scale and sediment, which can negatively affect plumbing, water heaters and water heating equipment.
• Drinking water quality: High TDS water may contain metal ions such as lead, cadmium and chromium, which can be harmful to health. Therefore, consumption of high TDS water may lead to chronic exposure to harmful substances.
• Soil and agriculture: The use of high TDS water for irrigation may lead to soil salinization, making the soil unsuitable for crops. This may have a negative impact on agricultural yields.
• Environment: Discharges of high TDS water may have negative impacts on the environment, including harm to the survival and habitat of aquatic organisms.
• Industrial applications: In industrial processes, high TDS water may lead to corrosion of equipment, generation of waste and impact on productivity, thus requiring higher water quality.
• Swimming pool water quality: High TDS water may lead to turbidity and degradation of swimming pool water, which requires more maintenance and water quality management.

Overall, high TDS water not only affects the taste, appearance and suitability of water, but can also negatively impact health, the environment and various applications. Therefore, monitoring and managing TDS levels is important to ensure clear, safe and fit-for-purpose water. Where required, appropriate water treatment measures such as reverse osmosis, distillation or deionization can reduce TDS and improve water quality.

TDS Limit Values and Recommended Solution Combinations for Different Scenarios

Application Scenario	TDS Reference Range / Control Target	Main Risks	Recommended Solution Combination
Drinking Water	Recommended ≤500 mg/L; China GB 5749-2022 sets the limit for total dissolved solids at 1000 mg/L; WHO does not set a health-based guideline value and mainly considers taste acceptability	Poor taste, salty flavor, high hardness, scaling, pipe deposits	Raw water testing + multimedia filtration + activated carbon filtration + softening / antiscalant dosing + RO reverse osmosis + UV / ozone / sodium hypochlorite disinfection + online conductivity / TDS monitoring
Residential / Commercial Direct Drinking Water	Common target: 30–300 mg/L, depending on taste and mineral retention requirements	High TDS affects taste; very low TDS may taste flat	PP filtration + activated carbon + RO / NF membrane + post activated carbon + optional mineralization cartridge + online or handheld TDS testing
Food and Beverage Water	Usually requires more stable water quality than ordinary drinking water. Many processes require low and stable TDS, commonly controlled at <100–300 mg/L, depending on the product process	Affects taste, formula stability, scaling, and batch consistency	Pretreatment filtration + activated carbon + softening / antiscalant dosing + RO + UV sterilization + precision filtration + online conductivity, pH, and residual chlorine monitoring
Industrial Boiler Feedwater	The higher the boiler pressure, the lower the required TDS. Low-pressure boilers may tolerate higher TDS, while high-pressure boilers usually require much lower levels	Scaling, foaming, carryover, corrosion, and increased blowdown	Multimedia filtration + water softener + RO + deaerator + chemical dosing system: antiscalant / oxygen scavenger / phosphate / alkalinity adjustment + online boiler water conductivity monitoring + automatic blowdown
Cooling Circulating Water	No fixed TDS limit; usually controlled by cycles of concentration. Commercial cooling towers commonly operate at 3–6 cycles, depending on hardness, alkalinity, silica, and chloride	Scaling, corrosion, microbial growth, and reduced heat exchange efficiency	Side-stream filtration + softening / antiscalant dosing + corrosion inhibitor + biocide / sodium hypochlorite / chlorine dioxide + online pH / conductivity monitoring + automatic blowdown and makeup water control
RO Reverse Osmosis System Feedwater	Designed according to membrane type and recovery rate. High TDS increases osmotic pressure, reduces permeate production, and increases scaling risk	Membrane fouling, membrane scaling, increased permeate TDS, and higher operating pressure	Sand filtration / multimedia filtration + activated carbon + softening or antiscalant dosing + cartridge filter + RO + CIP cleaning system + inlet and outlet conductivity monitoring
Pure Water / Laboratory Water	ASTM D1193 defines reagent water grades by conductivity / resistivity. Type I water requires extremely low conductivity, reaching 18 MΩ·cm level	Ionic residue, experimental error, and equipment contamination	Pretreatment + RO + EDI / mixed bed ion exchange + UV TOC reduction + terminal ultrafiltration / microfiltration + online resistivity, conductivity, and TOC monitoring
Agricultural Irrigation Water	FAO salinity risk classification: TDS <450 mg/L = low risk; 450–2000 mg/L = moderate risk; >2000 mg/L = high risk	Soil salinization, crop yield reduction, and difficulty in root water absorption	Raw water testing + filtration + RO / NF desalination when necessary + anti-clogging filtration for drip irrigation + pH adjustment + conductivity / salinity monitoring
Wastewater Reuse	Depends on the reuse purpose. TDS requirements vary for landscaping, flushing, cooling tower makeup water, and process water reuse. For RO-based reuse, hardness, silica, chloride, and organic matter must be controlled	Scaling in reuse pipelines, membrane fouling, corrosion, and salt accumulation	Biological treatment + coagulation sedimentation / DAF + multimedia filtration / ultrafiltration + activated carbon + RO / NF + disinfection + online COD, turbidity, conductivity, and pH monitoring
High-Salinity Wastewater / ZLD	TDS is usually several thousand to tens of thousands mg/L. Conventional biological treatment and filtration cannot remove dissolved salts effectively	High salinity inhibits biological treatment, causes membrane scaling, and increases concentrate disposal cost	Pretreatment + hardness removal / softening + UF + RO / NF + high-pressure RO / DTRO + evaporation concentration + crystallization + online conductivity / TDS and flow monitoring

Difference Between TDS and Water Hardness

TDS and water hardness are two water quality related parameters that are somewhat similar, but distinctly different:

TDS:

• TDS is the sum of all dissolved substances in water, including minerals, salts, metal ions, inorganic and organic substances.
• TDS is usually expressed in milligrams per liter (mg/L) or as a partial percentage to indicate the amount of dissolved substances in the water.
• The TDS measurement does not provide information on the specific type or chemical composition of dissolved substances; it is only a general indicator.

Water hardness:

• Water hardness is the amount of dissolved calcium and magnesium ions in water. These ions are usually in the form of Ca²⁺ (calcium) and Mg²⁺ (magnesium).
• Water hardness is usually expressed in units of hardness (mg/L or ppm) or grams per liter (gpg).
• Water hardness is a specific type of dissolved substance caused primarily by calcium carbonate and magnesium carbonate.

Parameter	TDS	Water Hardness
Definition	The total sum of all dissolved substances in water.	The concentration of dissolved calcium (Ca²⁺) and magnesium (Mg²⁺) ions in water.
Main Components	Minerals, salts, metal ions, organic substances, inorganic substances, etc.	Calcium (Ca²⁺) and magnesium (Mg²⁺) ions.
Units	Usually expressed in milligrams per liter (mg/L) or as a percentage.	Typically measured in hardness units (mg/L or ppm) or grains per gallon (gpg).
Information Provided	A general indicator of overall water quality but does not provide information about specific minerals or ions.	Provides specific information about the concentration of calcium and magnesium ions in water.
Relationship to Water Quality Characteristics	Can be caused by various types of dissolved substances, including metals, salts, minerals, and organic matter.	Primarily caused by calcium and magnesium ions, making it an indicator of water hardness or softness.
Application Areas	Used to measure the overall level of pollution in water but does not provide specific water quality characteristics.	Used to assess water hardness or softness and its impact on plumbing, water heating equipment, and industrial processes.
Examples	Seawater typically has high TDS due to the presence of various salts and minerals.	Groundwater may have varying degrees of hardness depending on the concentration of calcium and magnesium ions.

Summary

To reduce TDS in water, a variety of methods such as reverse osmosis, distillation, deionization, ion exchange, electrodialysis, chemical treatment, and dilution can be used. The choice of method should be based on specific needs, such as drinking water, industrial use or laboratory research, and to avoid contamination of the water source to prevent elevated TDS levels.

Apure offers not only TDS meter sensors etc., but also meters and sensors for parameters such as pH, ORP, conductivity, dissolved oxygen, chlorine, salinity, ozone and corrosion rate. Feel free to contact us.