Filtered water can taste bad because of an exhausted cartridge, a new filter that was not flushed, stagnant water, or a problem already present in the incoming supply. Taste alone does not identify the cause, so compare filtered and unfiltered water and note when the change began.
Compare taste before and after the filter
Taste cold water from the same supply before and after filtration, avoiding water that has sat in the faucet for hours. If only the filtered water tastes bad, the filter, housing, or flushing process is the likely branch.
A new cartridge may need flushing
Many filters need several gallons or liters of flushing to remove carbon fines and trapped air. Follow the manufacturer’s specified volume or time; if a chemical or plastic taste persists, verify the cartridge is correct and seated properly.
An exhausted filter may let source-water tastes through
If taste worsened gradually and the filter is near its rated capacity, treatment performance may have declined. Replace the cartridge on schedule rather than extending use simply because flow still seems normal.
A sudden whole-home taste or odor points upstream
If filtered and unfiltered water change at the same time, check utility notices, recent work, or well-water changes. Do not treat a household filter as protection from unknown contamination; follow official instructions during a health advisory.
Sources
- U.S. Environmental Protection Agency (EPA) — WaterSense Home Maintenance — Household water maintenance, leaks, fixtures, and efficiency.