Taste is a diagnostic tool. Here's the decoder.
Bad taste after filtration almost always points at one specific stage. Match your symptom:
| Taste / smell | Likely cause | Fix |
|---|---|---|
| Chlorine / pool smell | Carbon block exhausted — chlorine breaking through | Replace CTO carbon block; check membrane health after |
| Metallic | Old plumbing leaching, or membrane passing minerals it shouldn't | Test TDS — if rejection is low, membrane may be compromised |
| Stale / flat | T33 post-carbon exhausted, or water sat in tank too long | Replace T33; on tank systems, draw and refresh regularly |
| Fishy / musty | Biofilm in housings — system sat unused, or prefilters far overdue | Sanitize housings, replace all prefilters, flush thoroughly |
| Oily / chemical | New filters not flushed, or non-food-grade component | Flush per new-filter procedure; verify food-grade parts |
Before blaming the system: taste the water straight from the RO faucet into a clean glass, not through the fridge dispenser or an old bottle. Dispenser lines and dirty ice makers are guilty more often than you'd think.
A rotten-egg (sulfur) smell from both hot and cold taps usually comes from the well or municipal supply, not your RO — that's a water-source issue beyond a filter change. If only the hot tap smells, it's likely your water heater's anode rod. Filters can't fix source problems; they can only tell you where the problem isn't.
Probably just an exhausted carbon block. Carbon's whole job is eating chlorine; when it's spent, chlorine passes through. Replace it — and check your membrane, because chlorine damages TFC membranes.
Usually new filters that weren't flushed (carbon fines taste bitter), or a system that sat stagnant growing biofilm. Flush or sanitize; the system isn't 'worse than tap,' it's neglected.
Taste is about aesthetics, not safety — but treat persistent odd tastes as a signal to investigate, not to ignore. When in doubt, get a lab test; a $15 TDS pen can't detect everything.
Blame the ice maker line and bin, not the RO. Clean/sanitize the ice maker and replace its inline filter if it has one.
RO removes most minerals, so it tastes flatter than mineral-rich tap. That's the physics, not a defect. A T33 post-carbon stage rounds the taste back out.