Assess the causeFollow the evidence.
Review the source-water change, maintenance history, filter stages, storage condition and any need for suitable water testing.
The exact model and operating conditions determine which tests apply. These are possible inspection directions, not a list of components that must be changed.
Before the appointmentKeep the useful details.
Avoid drinking water with an unexplained change; use a known safe supply while the cause is assessed.
Record the timing, previous work and accessible model label. Do not remove covers or handle live, refrigerant or pressurised components to obtain information.