Common standards
| Standard | Typical scope |
|---|---|
| NSF/ANSI 42 | Aesthetic effects such as chlorine, taste/odor and particulate claims. |
| NSF/ANSI 44 | Residential cation-exchange water softeners. |
| NSF/ANSI 53 | Specific contaminant-reduction claims with health effects. |
| NSF/ANSI 55 | Ultraviolet microbiological treatment systems. |
| NSF/ANSI 58 | Reverse osmosis systems. |
| NSF/ANSI 401 | Certain emerging/incidental contaminant reduction claims. |
Certification is claim-specific
NSF explicitly notes that certification does not mean a product reduces every possible contaminant. Verify the listing for the exact claim you need.
Next step
Run your numbers through the Water System Planner, then verify any product against its actual service-flow, pressure-drop, capacity and certification data.