A whole house filter has two quite different lifespans depending on what is inside it. Cartridges are consumed by the volume of water passing through and the load they catch, measured in months. Media beds are consumed slowly by attrition and chemical exhaustion, measured in years. Both are better judged by evidence than by a date.
Sediment cartridges: months, judged by pressure
A sediment element blocks as it does its job, so it announces itself: pressure drop across the housing climbs and eventually the shower notices. Gauges either side turn that into a number and remove the guesswork entirely, and noting the reading when a cartridge is new gives you a baseline. On a clean municipal supply a cartridge may run most of a year; on a well carrying sediment it may need changing every few weeks, which is usually a sign the rating or the format is wrong for the load.
Carbon cartridges: volume, judged by nothing visible
Carbon has a capacity rather than a blockage point, so it gives no pressure warning and no clear taste cliff. It is changed on the manufacturer's rated volume against your household's real use, written on the housing as a date. What shortens it: high chlorine, a chloraminated supply that the media was not specified for, and any missing sediment stage upstream, since particles blind the surface and waste the media inside. A cartridge left in long past capacity is also a place bacteria will grow.
Media beds: years, judged by performance
Carbon in a backwashing vessel lasts years rather than months because there is far more of it, and it is replaced when the taste or chlorine returns rather than on a fixed schedule. Sediment media wears slowly by attrition and is topped up. Catalytic and oxidizing media lose activity over years. In every case the signal is a return of the problem the vessel was fitted to solve, or a pressure drop that a backwash no longer clears, rather than a date on a calendar.
Making the interval reasonable
If cartridges are being changed constantly, the system is undersized or the staging is wrong: a coarse cartridge ahead of a fine one, or a larger housing, usually resolves it. If a filter has been in for years because nobody noticed, fit gauges and write dates on housings. And size for peak flow rather than the space available, because an undersized housing shortens every interval it has. Our whole house filter cost guide covers what different sizes cost to run.
Questions people ask about how long does water filter last
How long does a whole house sediment cartridge last?
Months, and it varies enormously with the load. Pressure drop across the housing is the honest signal rather than a date.
How do I know when carbon is spent?
By rated volume and time, since carbon gives no pressure warning and no clear taste cliff before it stops working.
How long does media in a tank last?
Years rather than months, replaced when the original problem returns or when a backwash no longer clears the pressure drop.
My cartridges never last. What is wrong?
Usually undersizing or missing staging. A coarse cartridge ahead of the fine one, or a larger housing, normally fixes it.