Purikor 5-Stage Reverse Osmosis System

Purikor 5-Stage at a glance

Reverse osmosis works on a genuinely different principle than the ultrafiltration in our Evans systems, not just a finer version of the same idea. Ultrafiltration is pure size exclusion — a physical sieve. Dissolved ions like lead, arsenic, and fluoride are actually smaller than even the RO membrane's ~0.0001-micron rating, so a sieve alone wouldn't stop them. What does is the membrane's structure combined with pressure: it's semi-permeable, and pushing water through it under pressure — which is what the booster pump is for — lets water molecules pass while rejecting dissolved ions almost entirely, the same principle behind desalination at a much larger scale.

For heavy metals specifically, that mechanism is well studied. A peer-reviewed review of nanofiltration and reverse osmosis techniques for arsenic removal found RO rejection rates for pentavalent arsenic — the more common form in treated water — commonly in the 80–99% range, with lead removal typically reported even higher. Purikor's own manual publishes component-level rejection figures for its TFC membrane against the same NSF Standard 58 parameter list — lead and arsenic both at 99% — manufacturer data for the specific membrane in this system, not a system-wide certification, but a real number for the actual part we install.

Fluoride and nitrate travel with the same story: both dissolved at the molecular level, both pass straight through ultrafiltration untouched. A review in the journal Water catalogued arsenic, fluoride, and nitrate contamination across groundwater sources in northern Mexico specifically. That's not a CDMX finding, and we won't claim it is — municipal tap water here is treated before it reaches your building. But if fluoride or nitrate is a concern for you regardless of source, reverse osmosis is the only tier on our menu that addresses it: Purikor rates the TFC membrane at 98% fluoride rejection and 97% for nitrate.

One thing worth knowing before you book, that doesn't show up anywhere else on this page: the TFC membrane tolerates a maximum of 0.2 ppm chlorine in the water reaching it. CDMX municipal water is chlorinated well above that level, which is exactly why the carbon stages sit ahead of the membrane — their job isn't just taste, it's protecting a membrane that costs far more than the cartridges. An overdue carbon stage on this system isn't just a taste problem the way it is on an Evans system; it's the one maintenance lapse that can shorten the life of the most expensive part in the box.

See the full comparison across all four systems for what “partial” and “final-stage UV” mean in practice.

Also in Drinking Water Systems