Choose deionizing pitcher filtration for small-volume no-install use. Choose RO for higher daily volume and more predictable long-term economics.
How the technologies differ
Deionizing pitchers use ion-exchange media to remove dissolved ions until the resin is exhausted. RO uses membrane separation and sends a reject stream to drain or a waste tank.
TDS is not the whole story
Both can lower TDS substantially, but a TDS meter does not identify which contaminants are present or absent. Exact certification and lab data still matter.
Cartridge life
High-TDS source water can exhaust deionization cartridges quickly. RO membranes usually last much longer, although prefilters and postfilters still require replacement.
Best fit
A pitcher suits one or two users with modest volume. A countertop or under-sink RO system is generally better for a household using purified water every day.