Here’s the truth: you can combine them. Many labs use RO first to strip the bulk, then DI to polish it. That’s super pure water—the best of both worlds. But for your home? That’s overkill. Unless you’re a mad scientist disguised as a barista.
Also, maintenance is different. RO systems need new membranes every few years. DI resins exhaust and you have to replace them or regenerate them with acid and caustic chemicals. Fun for nerds, not for a Saturday afternoon.
Cost Check
RO systems are cheaper upfront. A decent under-sink unit costs $150-300. DI systems are cheap to buy, but the resins are pricey to replace. You’ll spend more over a year. Money talk: RO is friendlier to your budget day-to-day.
And let’s not forget: both need carbon pre-filters to remove chlorine. Chlorine destroys RO membranes and DI resins. So really, you’re buying a whole system, not just one magic box.
