How a pitcher does
what a plumbed system does.
Four filtration stages, three NSF standards. Engineering in the open, verification on a published timeline.
Four stages, in series.
Each stage handles a different category of contaminant. None of them is enough alone — and none of them is novel. The engineering is in how they sit together.
Sediment pre-filter — 5 µm
A pleated polypropylene mesh catches rust, sand, and particulate from old plumbing before they reach the active media. Without this stage the carbon block clogs in weeks.
Activated carbon block — 0.5 µm
Coconut-shell-derived activated carbon, compressed into a 0.5-micron block. Adsorbs chlorine, chloramines, pesticides, pharmaceuticals, and microplastics down to that threshold. The denser the block, the slower the flow — and the more contact time the contaminants get.
KDF + ATS redox media
A copper-zinc alloy (KDF) and titanium-based media (ATS). Heavy metals — lead, mercury, copper — are bound by an oxidation-reduction reaction with the alloy itself, not adsorbed. Different mechanism, different contaminants, both required for an NSF/ANSI 53 lead claim.
Selective ion exchange
The final stage is selective: it binds fluoride ions and removes them, but is engineered to leave magnesium and calcium largely intact. The result is ~30% TDS reduction — not the 99% of reverse osmosis. Water tastes alive, not flat.
What "NSF certified" actually means.
Most filter brands wave the NSF logo without telling you which standard. The number is the whole story. Three standards apply to drinking-water filters; Osma is certified to all three.
Aesthetic effects
Chlorine, taste, odor, particulate. The baseline standard most pitchers test against. Says nothing about health-related contaminants.
Health effects
Lead, mercury, VOCs, chromium-6. The serious standard — testing protocol requires sustained removal across the filter's entire claimed lifespan.
Emerging contaminants
PFAS (PFOA / PFOS), pharmaceuticals, pesticides, hormones. The standard most pitchers don't carry. NSF/ANSI P473 is the PFAS-specific subset.
Tested by people we don't pay.
Annual third-party testing by an accredited laboratory. The accreditation number is below — you can verify it independently.
Each year a fresh production-line pitcher is sent to an accredited third-party laboratory. They run the NSF/ANSI 53 and 401 protocols, document the methodology, and we publish the results — pass, fail, or middling.
Sample type: production-line. Test frequency: quarterly. Full certification publishing on a timeline this year — certification body and accreditation number disclosed at that time.
Request the test summary →Why we built this.
The shortest brand story we could honestly write.
We started Osma because we couldn’t find a pitcher that removed PFAS at the level reverse osmosis does. We built one that does, engineered it to NSF/ANSI 53 and 401 protocols, and committed to retesting every year and publishing the results.
Six people on the team. One factory partner, contracted to our spec. Every customer email lands in one of our inboxes — write to us, one of us writes back.
Saying it plainly.
The most useful part of any product page is the part that says what it doesn't do.
- Not for well water with bacteria — you need UV, not us.
- Not a softener — if your problem is limescale in the kettle, look elsewhere.
- Not a pre-checked subscription, ever. You opt in, deliberately.
- Not 100% pure water — we keep the magnesium and calcium, on purpose.
- Not endorsed by anyone we paid for an endorsement.
- Not the cheapest pitcher, and we don't try to be.