How to Tell the Difference Between Good and Bad RO Membranes in Water Purifiers

How to Tell the Difference Between Good and Bad RO Membranes in Water Purifiers
How to Tell the Difference Between Good and Bad RO Membranes
To distinguish between good and bad RO membranes, you should primarily consider five key characteristics: desalination rate, flux, durability, stability, and material quality and certifications. High-quality membranes feature a high desalination rate, stable flux, resistance to contamination, a long service life, and safe materials.

01. Core Performance
1. Desalination Rate (Filtration Precision): The percentage of dissolved salts, heavy metals, bacteria, and other contaminants retained by the membrane.
2. Pure Water Flux (Flow Rate): The volume of water produced per unit area per unit time (commonly measured in LMH or GPD).
3. Durability (Fouling Resistance + Lifespan): High-quality membranes feature hydrophilic modification, wide flow channels, and anti-fouling coatings, making them resistant to scaling and clogging.
4. Operational Stability: During long-term operation, the desalination rate and flux exhibit minimal fluctuation (deviation ≤ ±5%); they have a wide temperature and pH tolerance range (high-quality membranes typically operate at pH 2–12 and temperatures of 5–45°C); Chlorine Resistance: Household membranes generally tolerate free chlorine levels of ≤0.1 mg/L; exposure to higher concentrations can cause oxidation and damage.

02 Materials and Manufacturing Processes
Membrane Material:
High-quality: Aromatic polyamide composite membrane (mainstream, high desalination rate, good stability).
Low-quality: Recycled materials, inferior polyamide; prone to leaching and damage.

Winding Process:
High-quality: Tight winding, uniform flow channels, secure center tube, and sealant free of bubbles.
Low-quality: Loose winding, uneven flow channels, prone to leakage, and prone to cross-contamination.

Visual Inspection:
Membrane elements: No deformation, no damage, no unusual odors, and clear labels (brand, model, specifications).
End faces: Even sealant application, no cracks, and no missing sealant.

03 Quick Self-Test Methods for Household Membranes

Test TDS: When feedwater TDS is 500 ppm, high-quality membranes should produce water with **＜50 ppm**; if **＞100 ppm**, the membrane has failed.
Observe Output Water: Stable flow, no bubbles, no odor; if flow fluctuates or has an odor, the membrane may be damaged or contaminated.
Check the Wastewater Ratio: For a first-class water efficiency rating, the ratio should be **≥2:1** (2 cups of purified water to 1 cup of wastewater); a ratio that is too low (＜1:1) wastes water and damages the membrane.
Check Lifespan: If replacement is needed **within 1 year**, the membrane is likely of poor quality.