How Often Should You Replace a Water Filter?

Start with the exact cartridge

The right replacement date belongs to the cartridge and system you own, not to water filters as a single category. Check the label, installation date, instructions and any rated volume limit. Do not extend a specified maximum interval simply because the water still tastes normal.

What the Purest listings currently recommend

The listed 10-inch sediment cartridge and CTO carbon cartridge recommend six-monthly replacement. The combined single-housing cartridge lists twelve months. These are product-specific recommendations, not a guarantee that every installation can run for that long.

Confirm that your installed parts match those listings. Greater use, changes in supply conditions or a manufacturer's capacity limit can mean an earlier replacement is needed.

Single cartridge, twin housing or RO

A combined cartridge is not interchangeable with a sediment and carbon twin set. Check the housing and part numbers before ordering. For reverse osmosis, record the membrane and each other stage separately. Do not assume that every component is replaced together or that a replacement set necessarily includes the membrane.

Keep a useful maintenance record

Record the equipment model, cartridge numbers, date fitted and next date or capacity limit. Keep the instructions available to whoever will perform the work. For a serviced commercial rental, use the schedule in the actual agreement rather than copying a residential cartridge interval.

Sudden discolouration, a chemical smell or illness concerns call for current provider advice, not an automatic conclusion that the filter is simply overdue. Send Purest the model and cartridge label when you need help identifying the next service.

Reference: CDC household water-system care guidance. Follow the maintenance instructions for the installed equipment.

Copy reviewed 6 October 2026. Check the current product listing, instructions and any applicable offer before ordering.