A technical guide to understanding RO membrane technology, selection, care, and the Crystal Quest® membrane product line.
A reverse osmosis membrane is a semi-permeable thin film composite (TFC) barrier that allows water molecules to pass through under pressure while blocking dissolved salts, heavy metals, PFAS, nitrates, bacteria, viruses, and virtually all other contaminants. The membrane is the heart of any RO system — its quality and condition determine the purity of the output water.
THUNDER© — Freshwater membranes for water with TDS below 2,000 ppm. Low-energy design reduces operating pressure and electricity consumption. Available in 50, 75, 100, and 200 GPD for residential systems, and in larger configurations for industrial use. ISO 9001:2015 certified from Scientific World Products©.
VIPER© — Brackish water membranes for TDS between 1,000 and 10,000 ppm. Designed for groundwater, wells, and estuarine sources. Higher operating pressure than freshwater membranes. Available in standard and low-fouling configurations for water with elevated silica or organic content.
SHARK© — Seawater desalination membranes for TDS up to 35,000 ppm. Operates at 800–1,000 psi. Fiberglass pressure vessel compatible. Available in 4-inch residential and 8-inch industrial element sizes.
| Ion / Contaminant | % Rejection | Ion / Contaminant | % Rejection |
|---|---|---|---|
| Calcium | 95–98% | Bromide | 93–96% |
| Sodium | 94–98% | Phosphate | 97–98% |
| Magnesium | 95–98% | Sulfate | 97–98% |
| Iron | 97–98% | Silica | 85–90% |
| Lead | 96–98% | Nitrate | 92–95% |
| Mercury | 95–97% | Fluoride | 93–95% |
| PFAS/PFOA | 95–99% | Bacteria | 99%+ |
| Arsenic | 95–98% | Boron | 60–70% |
*Nominal rejection values. Actual performance varies with feed water chemistry, temperature, pressure, and TDS. Not a performance guarantee.
Meeting minimum feed water requirements is critical. Failure to do so will cause membranes to foul prematurely and may void warranty.
| Parameter | Maximum | Parameter | Maximum |
|---|---|---|---|
| Free Chlorine | <0.1 ppm | Manganese | <0.05 ppm |
| Total TDS | <2,000 ppm | Organics (TOC) | <1 ppm |
| Turbidity (SDI) | <5 | Silica | <1 ppm |
| pH | 3–11 | Iron | <2 ppm |
| Temperature | 40°F–105°F | Hardness | <15 GPG |
With proper pretreatment and feed water conditions, TFC RO membranes typically last 2–5 years. Signs that a membrane needs replacement include: permeate TDS rising significantly above baseline, dramatically reduced production rate, or system pressure readings outside normal range. Annual cartridge replacement and periodic membrane testing with a TDS meter helps you track performance over time.
Because reverse osmosis removes virtually all dissolved minerals, the permeate water is slightly acidic (pH 5.5–6.5). For drinking water, remineralization using an alkalizing post-filter restores beneficial minerals (calcium, magnesium) and raises pH to a healthy 7.5–8.5 range. This is included in our Thunder© 2000C and alkalizing countertop configurations.
Browse THUNDER©, VIPER©, and SHARK© membranes for your system.