When should a home carbon filter be replaced?

Identify what is installed

A refrigerator cartridge, under-sink cartridge and whole-home carbon tank have different service arrangements. Photograph the model label, cartridge or tank information, and any display. Ask the installer which water outlets it actually treats.

Keep the installation manual and performance sheet. If you do not know the current cartridge, verify it before ordering a look-alike replacement.

Use capacity and conditions, not a universal calendar

Write down the manufacturer's time or gallon limit and how to track it. Household use and incoming water conditions can matter. A return of taste or odor may signal a problem, but waiting for one is not a reliable way to preserve a certified reduction claim.

EPA's home-treatment guide stresses that systems need ongoing maintenance and that cartridges should be replaced according to the manufacturer's directions.

Reference: EPA WaterSense home-treatment maintenance guide

Keep the certified configuration intact

If you bought the filter for a specific reduction claim, check that the replacement cartridge is part of the certified configuration. A generic cartridge that fits the housing may not carry the same claim.

After service, record the part number, date and next due point. Ask what flushing or sanitizing step the manufacturer requires before drinking from the unit.

Reference: NSF drinking-water treatment standards

Know when to call rather than replace

A leak, unusually low flow, a sudden whole-home pressure change, or an unfamiliar valve arrangement deserves diagnosis. Do not force a housing or bypass a device you cannot identify.

If the supply itself has an official advisory, follow the issuing authority. A scheduled carbon change is not a response to every water-quality event.