Concern → evidence → treatment
Water contaminant and treatment guides
The same symptom can have multiple causes, and the same technology can carry different verified claims from one model to another. This library shows where responsible research begins.
Aesthetic concern
Chlorine in tap water
To assess chlorine in tap water, open the current Consumer Confidence Report and recent utility notices. Record whether the disinfectant is free chlorine, chloramine, or a temporary switch between them, then note the reported residual range, Maximum Residual Disinfectant Level comparison, and any violation. A chlorine-like smell alone does not identify the disinfectant or prove that a regulatory limit was exceeded.
Exact NSF/ANSI 42 chlorine or chloramine claim
Disinfectant chemistry and contact time matter; carbon systems are not interchangeable. Open guide →
Water characteristic
Hard water and scale
Obtain a current hardness result for the water entering the home, reported in milligrams per liter as calcium carbonate or grains per gallon. Start with the utility's current water-quality information for public water, then use a tap test when a range is too broad for sizing. Private-well owners should use a qualified laboratory and test beyond hardness because other chemistry can change the treatment choice.
NSF/ANSI 44 ion exchange or a narrow conditioning claim
Hardness is different from chlorine, sediment, iron, or a health-effect contaminant. Open guide →
Health concern
Lead in drinking water
Obtain three records before comparing products: your utility's service-line inventory entry, the current Consumer Confidence Report or public notice, and a tap-water result collected under instructions suited to your question. Lead can enter water from a service line, solder, faucets, fixtures, or galvanized plumbing after water leaves the treatment plant. A utility-wide result cannot establish the concentration at one kitchen tap, and lead cannot be reliably identified by sight, taste, or smell.
Exact certified lead-reduction claim
A utility report may not capture lead contributed by a home’s service line or plumbing. Open guide →
Health concern
PFAS water filters
Start with a dated laboratory result or your public water system's current PFAS disclosure. Record every named compound, its concentration, the unit, the reporting limit, the sample location, and the method. EPA Methods 533 and 537.1 together can measure 29 named PFAS in drinking water, but a report may cover a smaller panel. A result for PFOA and PFOS does not establish the concentration of every chemical in the PFAS class.
Exact PFOA or PFOS claim under NSF/ANSI 53 or 58
Certification thresholds and named compounds must be read carefully. Open guide →
Well-water chemistry
Iron and manganese in well water
Order a certified-laboratory test for iron, manganese, pH, hardness, alkalinity, and locally relevant health contaminants. The color of a stain cannot tell you the concentration, chemical form, or complete treatment train.
Chemistry-specific treatment with adequate backwash
A sediment cartridge is not a universal solution for dissolved iron or manganese. Open guide →
Microbiological concern
Bacteria and microorganisms in private wells
Use the laboratory’s exact total-coliform and E. coli result and follow your state or local health department’s immediate-use instructions. If the result indicates fecal contamination, use a safe alternative source until officials say the water can be used again.
Source correction and validated treatment
Do not select UV from symptoms alone; pretreatment and system class matter. Open guide →