Quick take
Read the utility report and test the tap when needed. Use point-of-use treatment for drinking-water contaminants and whole-house treatment only when the concern genuinely affects every fixture.
Chlorine or chloramine
Carbon is the core treatment category. Chloramine usually pushes the design toward catalytic carbon or longer contact time.
Lead and old plumbing
Tap-level lead can come from service lines or building plumbing. Certified under-sink carbon or RO can be appropriate after testing confirms the problem.
PFAS and dissolved contaminants
Certified RO or carbon can be used at the drinking-water tap. Whole-house PFAS treatment is a larger project that should be justified by treatment scope.
Hard water
Hardness is separate from filtration. If scale is the problem, a true softener solves a different problem than a carbon filter.