Diagnosis
New filter media flavor or carbon dust. Fresh filters need a flush to remove fine particles and saturate the carbon, which can impart an initial off-taste.
How to Fix It
Flush the filter properly. After installing, slowly fill the entire 23-cup reservoir with tap water and dispense it ALL out through the tap. Do this twice. The third reservoir should taste normal.
If That Didn't Work
Check the manufacturing date on the filter box. Old stock (over a year) can sometimes develop a stale taste. Contact ZeroWater customer service for a replacement if flushing doesn't solve it.
Heads Up
Always flush a new filter with at least two full tanks of water before drinking. Skipping this step is the #1 reason for bad taste after a filter change.