Cryptosporidium in Water
The short answer on cryptosporidium
Cryptosporidium oocysts (4–6 microns) are the most chlorine-resistant common water pathogen — the reason Milwaukee's 1993 outbreak sickened 400,000+ people *through a treatment plant operating within the rules of its day*. Boiling (1 minute) and 1-micron *absolute* filtration (NSF/ANSI 53 cyst claim) are the verified answers; standard chlorination and unclaimed carbon filters are not. Immunocompro… The details — sources, official limits and honest removal methods — are in the complete guide: The complete cryptosporidium guide.
How to remove cryptosporidium — what actually works
| Technology | Where it lives | What to demand on paper |
|---|---|---|
| UV / 0.5μm | Point-of-use or whole-house system per spec | Named NSF/ANSI protocol or third-party lab sheet for the exact model |
If a listing claims cryptosporidium reduction and cannot name the standard or show the lab sheet, assume it does not have one. That single check filters out most of the market.
Can your refrigerator filter handle cryptosporidium?
No — standard carbon cartridges are not engineered for it. The technologies above are the ones that address it; your fridge filter still does its own job (chlorine, taste, and with a 53 claim, lead and cysts). Fridge cartridges are built for chlorine, taste and odor (NSF/ANSI 42), plus lead and cysts on certified 53 tiers. If cryptosporidium is your concern, keep the fridge cartridge for what it does well and put the right technology where you drink: see what your fridge model takes, then match the removal stage to the contaminant.
Often found together
- Bacteria in water — same source profile or shared treatment media; check your test report for the neighbor line items.
- E. coli in water — same source profile or shared treatment media; check your test report for the neighbor line items.
- Coliform in water — same source profile or shared treatment media; check your test report for the neighbor line items.
Cryptosporidium questions, answered straight
Does boiling water remove cryptosporidium?
Boiling is a concentration step, not a filter: water leaves as steam and whatever is dissolved stays behind, so levels rise by roughly the volume lost. The only heat-based method that works is distillation — capturing and condensing the steam. For cryptosporidium specifically, see the full guide.
Is my refrigerator water filter enough for cryptosporidium?
No — standard carbon cartridges are not engineered for it. The technologies above are the ones that address it; your fridge filter still does its own job (chlorine, taste, and with a 53 claim, lead and cysts). Match the technology to the contaminant, not the badge on the box.
How do I find out my actual cryptosporidium level?
On city water, your utility's annual Consumer Confidence Report lists it free. On a well, a lab mail-in panel is the reliable route — the test-first card above links our guide to reading the results.
What removes cryptosporidium from drinking water?
The technologies with a track record for cryptosporidium: uv / 0.5μm. Claims worth having come with a named standard (NSF/ANSI protocol or third-party lab sheet) — buy where the certificate names the exact part number.
Go deeper
Every contaminant, one page each
48 water problems from EPA primary, secondary and unregulated lists — sources, official limits, and which filters actually work (and which honestly don’t). Browse the Water Problems A–Z →