Choosing a water purification system should begin with measured water quality, not attractive product claims. EPA Maximum Contaminant Levels, or MCLs, define enforceable limits for many contaminants in public drinking water. Obtain a recent water quality report from your utility. For private wells, arrange testing through a qualified, accredited laboratory.
Test for lead, arsenic, nitrate, bacteria, and other local concerns. Results need units, sampling dates, and laboratory methods. Without those details, comparisons become unreliable.
Compare each result with the relevant EPA MCL. A result below the limit does not mean the water contains nothing harmful. It indicates compliance under defined testing conditions. Results above an MCL require careful attention and professional guidance.
Some emerging contaminants have health advisories rather than enforceable MCLs. That distinction matters. Do not treat every number as equivalent.
Match the system to the contaminant and its concentration. Activated carbon may reduce certain chemicals, while reverse osmosis can address dissolved substances. Ultraviolet treatment targets microorganisms but does not remove metals.
Check independent performance certification, replacement schedules, flow rate, and waste production. A system that removes lead may not remove nitrate. That mistake is common.
Re-test after installation and follow maintenance instructions. Filters can become less effective when neglected, even when the equipment still looks clean. I would also question a single test result, because sampling errors and changing conditions can distort the picture.