TDS values, RO membranes... How much do you really know about those technical terms in water purifiers?

Still feeling overwhelmed by all the jargon when shopping for a water purifier? RO membranes, TDS values, flow rates... How do you make sense of these concepts? How do you choose? Let's dive into 10 key terms in water purification. Whether you're selecting a model or using your machine daily, you'll be able to pinpoint your needs precisely—no more letting salespeople lead you by the nose~

RO Membrane (Reverse Osmosis Membrane)

The RO membrane, or reverse osmosis membrane, is the core filtration component of water purifiers and one of the most advanced filtration technologies currently available for home use. It functions as a semi-permeable membrane with selective permeability. When subjected to pressure exceeding the osmotic pressure of the source water, it allows only small molecules like water molecules and dissolved oxygen to pass through. In contrast, it traps bacteria, viruses, heavy metal ions (lead, mercury, cadmium, etc.), inorganic salts, scale, pesticide residues, antibiotics, and other impurities are retained. With a filtration precision of 0.0001 microns—equivalent to one millionth of a human hair's diameter—the filtered water approaches pure water quality and is safe for direct consumption.

When selecting and using the system, note that RO membrane quality directly determines purification effectiveness. High-quality RO membranes offer longer service life. Additionally, RO membranes require regular flushing and maintenance to prevent impurity buildup that could reduce flow efficiency.

Flow Rate

Flow rate indicates the cumulative purified water volume produced by the water purifier within 24 hours, measured in gallons (1 gallon ≈ 3.785 liters). This value directly determines the water dispensing speed—a higher flow rate means faster water delivery, eliminating lengthy wait times when filling containers.

When selecting a model, consider household size: a 600G+ unit suffices for 3-4 people. Larger families or those with high water demand should prioritize 800G or 1000G high-flux models for efficient, convenient use—whether washing vegetables, cooking, or direct drinking.

TDS Value (Total Dissolved Solids)

TDS stands for Total Dissolved Solids, representing the total mass of dissolved solids (including inorganic salts, heavy metal ions, soluble organic matter, etc.) in one liter of water, measured in milligrams per liter (mg/L). Generally, a lower value indicates fewer dissolved impurities and relatively purer water. For example:

- Tap water typically has a TDS value between 50-300 mg/L.

- Pure water filtered through RO membranes usually has a TDS value below 10 mg/L.

- Mineral water generally has a TDS value between 50-500 mg/L.

However, note that TDS should not be the sole criterion for judging water quality. It only reflects the “amount of impurities” present but cannot determine whether those impurities are “harmful or beneficial.” For instance, mineral water has a higher TDS than purified water but contains minerals essential for the human body. Conversely, contaminated water may have a low TDS yet contain harmful organic compounds. Assessing water quality requires considering multiple indicators comprehensively, such as residual chlorine, total bacterial count, and heavy metal content.

Water Efficiency Rating

The water efficiency rating is a nationally mandated label indicating a water purifier's water usage efficiency. Classified under national standard GB 34914-2021, it ranges from Level 1 to Level 3. Grade 1 represents the highest water efficiency, typically achieving a water production rate of ≥60%. This means that for every 100 liters of raw water consumed, at least 60 liters of purified water are produced. Grade 2 achieves a production rate of ≥55%, while Grade 3 achieves ≥50%.

This rating directly impacts long-term water usage costs. Prioritizing Grade 1 models during purchase can yield significant water bill savings over time, making them particularly suitable for households with high water consumption.

Integrated Water Path

Integrated water path represents a novel internal piping design for water purifiers. It consolidates traditionally dispersed pipes into a unified system, reducing the number of pipe connections. This design offers superior sealing, effectively lowering leakage risks by preventing water seepage or leaks caused by loose or aged connections. Additionally, the compact integrated water circuit saves internal space within the purifier, resulting in a sleeker overall appearance. It also allows for installation in tighter spaces. Commonly found in high-end water purifiers, prioritizing this design enhances both safety and convenience during use.

Rated Total Water Purification Capacity

Rated purification capacity refers to the cumulative volume of water a filter cartridge can effectively process under specified conditions, measured in liters. This is a core indicator of a filter cartridge's lifespan. When the cumulative water output reaches this value, the filter's performance will noticeably decline—for example, filtered water may retain impurities or flow more slowly—signaling the need for replacement. When selecting a model, consider this value: a higher rated water purification capacity indicates a longer filter lifespan, reducing replacement frequency and lowering long-term maintenance costs. For instance, a water purifier with a 4000L rated capacity offers double the filter lifespan compared to a 2000L model.

Dual Water Output

Dual water output is a practical design feature in water purifiers, simultaneously providing both household water and direct drinking water to meet diverse household needs. Household water undergoes fine filtration for daily boiling and cooking, while direct drinking water undergoes deep filtration through an RO membrane, ensuring pure, safe consumption. This design offers multiple advantages: it prevents wasting high-cost purified water on routine cleaning, ensures safe drinking water quality, reduces the frequency of RO membrane replacement, and extends its lifespan, delivering superior cost-effectiveness.

Wastewater Ratio

The wastewater ratio indicates the volume ratio of purified water to wastewater produced during operation. Common ratios include 1:1, 2:1, and 3:1. A higher ratio signifies less wastewater generated during purification, resulting in greater water savings. For example, a 3:1 ratio means producing 3 liters of purified water generates only 1 liter of wastewater. However, note that in areas with poor water quality, blindly pursuing a high waste water ratio is not recommended. When the source water contains excessive impurities, a high waste water ratio increases the filtration pressure on the RO membrane, potentially leading to membrane element clogging and accelerated wear. Appropriately lowering the ratio can extend the lifespan of the RO membrane.

Residual Chlorine

Residual chlorine is the effective chlorine remaining after tap water disinfection. Water treatment plants typically use chlorine gas to disinfect water, eliminating bacteria, viruses, and other microorganisms to ensure water quality safety during distribution. However, some residual chlorine remains in the water post-disinfection. Excess residual chlorine can irritate skin and respiratory mucous membranes, potentially causing discomfort with prolonged exposure. Furthermore, residual chlorine may react with organic compounds in water to form carcinogens like chloroform, posing health risks. Activated carbon filters in water purifiers effectively adsorb residual chlorine while also removing off-colors and odors, improving water taste.

Hard Water vs. Soft Water

Hard water and soft water are classified based on calcium and magnesium ion content. Hard water contains higher levels of these ions. When heated, calcium and magnesium ions combine with carbonate ions in the water to form insoluble precipitates like calcium carbonate and magnesium carbonate—commonly known as scale. Scale not only adheres to the inner walls of kettles and water heaters but also clogs the pipes and filter cartridges of water purifiers, shortening the lifespan of these appliances. Additionally, washing clothes with hard water makes fabrics stiff and reduces cleaning effectiveness. Softened water, on the other hand, uses ion exchange technology to remove most calcium and magnesium ions, reducing water hardness. This makes it less prone to forming scale when heated, making it ideal for laundry and bathing. It also effectively protects appliances like water purifiers, water heaters, and washing machines, extending their lifespan.

Choosing a water purifier fundamentally boils down to “matching your needs.” Understanding these terms and selecting based on your household's water quality, installation conditions, and usage scenarios ensures you make the right choice. In hard water areas, prioritize water softening functionality. For larger households, opt for high-flow models. Families requiring both direct drinking water and general household use will find dual-outlet designs more cost-effective. Selecting based on your specific requirements prevents unnecessary spending.