Quick take
Start with cleaning, filter age, tank seating and a full power reset. Separate purification problems from hot/cold dispensing problems before deciding the unit needs service.
Filter alerts and taste changes
Aging cartridges can affect taste and flow. Follow the actual replacement schedule rather than only resetting the indicator.
Hot or cold water not reaching expectations
Check selected temperature mode, ambient conditions, tank fill level and whether the unit has had enough recovery time.
TDS questions
Remineralization can intentionally raise final TDS. Diagnose membrane performance using the correct sampling point.
Cleaning and stagnation
Countertop tanks and internal water paths need periodic cleaning. Long periods of non-use can create stale taste even when filters are not exhausted.