A sudden shift in how your drinking water tastes is unsettling, but it's rarely mysterious — RO systems have a limited number of components that affect taste, and each produces a fairly specific symptom. Here's how to narrow down the cause.

1. Water tastes flat or metallic

This is almost always a TDS controller issue — the valve that blends a small amount of pre-filtered water back into the output to retain natural minerals may be set too low, stripping the water of essentially all dissolved minerals. Recalibrating the TDS ratio usually resolves it within one visit.

2. Water tastes heavier or slightly salty

The opposite problem — the TDS bypass ratio is letting through more unfiltered water than it should, or the membrane's rejection rate has dropped. Testing output TDS against source TDS will tell you which one it is.

3. Chlorine or chemical smell

This points to a saturated carbon filter — it's the stage responsible for removing chlorine, and once it's exhausted, that smell passes straight through, well before any other symptom shows up.

4. Taste changed right after a filter or part replacement

New filter cartridges sometimes carry manufacturing residue that needs to be flushed out before use — a brief odd taste in the first day or two after a change is common and usually resolves itself as the system flushes through.

5. Slightly musty or stale taste

If the storage tank hasn't been cleaned in a while, this is a common cause — sediment and biofilm can build up inside the tank itself, independent of how well the filters are working. A tank clean, included in most standard servicing visits, usually fixes this.

6. Taste varies depending on time of day

This can point to source water variability rather than the RO itself — municipal supply quality sometimes shifts depending on the time of day or which part of the network is feeding your area. Testing source TDS at different times can confirm whether this is the cause.

Frequently asked questions

What's a normal TDS level for good-tasting RO water?

Generally 50–150 ppm is considered a good range for taste and mineral content, though personal preference varies. Below 50 ppm often tastes flat; above 150 ppm can start tasting heavier.

Is a taste change always a sign something is wrong?

Not always — a brief taste change right after a filter change is normal. But a taste change with no recent service, especially a chemical or chlorine smell, is worth checking rather than ignoring, since it usually means a filter stage has become saturated.