One of the first decisions in choosing a water filter is scope: do you want to filter all the water in your home, or just the water you drink? Each approach has clear advantages depending on your water quality issues.
Under-sink (point-of-use) systems
These install under your kitchen sink and filter water at a single tap - usually through a separate faucet mounted next to your main one.
Best for: Removing drinking water contaminants like lead, PFAS, arsenic, nitrates, chlorine taste, and disinfection byproducts. Reverse osmosis under-sink systems provide the most thorough filtration available for residential use.
Cost: $50–$400 for the system, $30–$100/year for replacement filters. Installation is DIY-friendly for most models.
Limitations: Only filters water at one tap. Doesn't help with shower water, laundry, or other fixtures. If your concern is skin/hair issues or whole-house contaminants, this won't solve it.
Whole-house (point-of-entry) systems
These install on the main water line where it enters your home, treating all water before it reaches any fixture.
Best for: Chlorine/chloramine removal (improves shower water too), sediment, iron and manganese staining, and general water quality improvement throughout the home. Essential for well water with bacterial or sediment issues.
Cost: $300–$3,000+ depending on type and capacity, plus $100–$300/year for maintenance. Professional installation recommended ($200–$500).
Limitations: Whole-house carbon filters don't remove contaminants as thoroughly as under-sink RO systems. You're trading breadth (all taps) for depth (how much is removed). Not effective for PFAS at low concentrations or dissolved heavy metals.
The best setup for most homes
If your water has specific contaminant concerns (lead, PFAS, arsenic), start with an under-sink RO system for your drinking water. This addresses the highest-priority health concern - what you're actually ingesting.
If you also have aesthetic issues throughout the house (chlorine smell in showers, sediment, iron staining), add a whole-house carbon or sediment filter. The two systems complement each other: whole-house for broad improvement, under-sink for thorough contaminant removal at the kitchen tap.
If you have hard water, a water softener goes on the main line (whole-house treatment) since scale affects all plumbing and appliances.
Check your water quality on ClearWater to see what contaminants are in your water - that determines which approach makes sense.