Cartridges, membranes, and resin — what each one does.

All RO membranes are rated for a specific stabilized salt rejection. Many retail membranes stabilize around 94–96% rejection.

SpectraPure tests every membrane we ship and stands by 98% standard rejection and 99% on SpectraPlus.

Why it matters: the higher the rejection, the more impurities are removed before the DI stage. Higher TDS reaching DI means faster resin exhaustion and more frequent filter changes. Picking the right pre-filters (sediment and carbon) is just as critical — they protect the membrane and extend the life of every stage downstream.

Sediment filters remove larger particles like sand and silt. Effectiveness is measured by the micron rating — the size of particles the filter pore can capture. Smaller rating = finer filtration.

20 micron: common first-stage rating — captures sand and some algae.
10 micron: typical second-stage — captures smaller particles and larger microorganisms.
5 micron: removes clay, silt, and finer sediments.
1 micron: very fine particles and some microorganisms.

Sediment filters come in several physical formats. Each trades off cost, capacity, and reusability:

Pleated: accordion-shaped, large surface area, often washable and reusable.
String-wound: string wound around a core — winding tightness sets the micron rating.
Spin-down: spinning action separates sediment; usually a pre-filter for coarse debris.
Melt-blown / spun: polypropylene depth filtration with pore size decreasing toward the center.
Bag filters: filtering bags used in industrial applications with high sediment loads.

Carbon adsorbs chlorine, chloramines, and organics — protecting the membrane and improving taste. Micron rating still matters for what passes through:

5 micron: high flow, good for sediment removal and whole-house systems; modest pathogen protection.
1 micron: captures many bacteria and parasites including E. coli, Salmonella, Shigella, and some viruses like HAV.
0.5 micron or less: ultra-fine — removes most bacteria, cysts, protozoa, PFAS, microplastics, lead, and heavy metals. Standard for high-purity drinking water.

Different resins for a reason. We test resins from around the world to produce the highest-quality DI cartridges on the market.

Custom formulas for higher purity. Every cartridge is formulated and produced in our Tempe warehouse — and has been for 30+ years.

MaxCap: roughing filter that keeps downstream stages healthy.
SilicaBuster: high-capacity for areas with high silica content.
Mixed-Bed: our flagship blend delivers a consistent 18.2 MΩ·cm (0 TDS) — the theoretical maximum purity of water — and lasts longer at higher capacity than any other retail resin on the market. Independently tested against every major competitor.
Bulk resin & refillable cartridges: plus high-capacity versions with 33% more capacity than standard.

Higher capacity than competitors, higher purity than anyone else. Every cartridge is hand-built, packaged, and tested before it ships.

Production rates depend on source TDS, pressure, flow restrictor, and water hardness. When you see a system advertised as 2:1 or 1:1, it's usually marketing — the unstated cost is more frequent membrane replacement.

Most homes have hard water. Standard RO systems run at 3:1 to extend membrane life and prevent excessive TDS creep, plus prevent calcium/magnesium from scaling the membrane.

To run 2:1 you need a water softener on the source.
To run 1:1 you need: (1) pure-water flush to rinse the membrane, (2) a booster pump to maintain pressure, and (3) soft water.

SpectraPure designs systems that last — tested in Tempe, AZ on some of the worst water in the nation.