Reference
Water filter glossary
Plain-English definitions for every term you will encounter in a water filter review or your water quality report.
Filtration Technology
Activated Carbon
Activated carbon is the filtration media used in most pitcher filters, faucet filters, and whole-house carbon systems — what it removes, what it does not, and the difference between granular activated carbon (GAC) and carbon block.
Reverse Osmosis
Reverse osmosis (RO) forces water through a semi-permeable membrane with pores small enough to reject dissolved contaminants — including lead, PFAS, fluoride, and arsenic — while allowing water molecules to pass.
Water Quality
GPD (Gallons Per Day)
GPD (Gallons Per Day) is the production rate rating for reverse osmosis systems — how to interpret it accurately and why real-world output is usually 40–60% of the rated figure.
TDS (Total Dissolved Solids)
Total Dissolved Solids (TDS) measures all dissolved substances in water including minerals, salts, and contaminants — a TDS meter reading does not distinguish between beneficial and harmful dissolved solids.