Traditional systems can waste 3–4 gallons for every 1 gallon purified. Look for high-efficiency models with a 1:1 or 2:1 ratio .

Ensure the system actually removes what you're worried about. Reverse Osmosis Water Filter: Guide to Buying and Choosing

RO removes everything, including good minerals, which can make water taste "flat." Systems with a remineralization stage add calcium and magnesium back for better taste and pH balance. 3. Evaluate Filtration & Certifications

Uses an internal pump to provide water on demand. It is compact and wastes less water but requires an electrical outlet.

Most common and affordable ($300–$750). Stores water in a tank for instant access, but takes up significant space.