Legionella in Water
The short answer on legionella
Legionella — the bacterium behind Legionnaires' disease — breeds in warm, stagnant building plumbing (77–108°F is its comfort band): hotels, hospitals, cooling towers, large apartment systems. Ordinary single-family homes are low-risk; the honest household answer is usually water-heater temperature discipline, not a filter. In fact, point-of-use cartridges are the *wrong* purchase here — stagnatio… The details — sources, official limits and honest removal methods — are in the complete guide: The complete legionella guide.
How to remove legionella — what actually works
| Technology | Where it lives | What to demand on paper |
|---|---|---|
| UV + disinfection | 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 legionella 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 legionella?
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 legionella 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.
Legionella questions, answered straight
Does boiling water remove legionella?
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 legionella specifically, see the full guide.
Is my refrigerator water filter enough for legionella?
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 legionella 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 legionella from drinking water?
The technologies with a track record for legionella: uv + disinfection. 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 →