How often should you change a whole-house water filter?
Updated July 2026
Change a whole-house sediment cartridge every 3 to 6 months and a carbon block every 6 to 12 months. Well water and heavy silt shorten both; clean city water stretches them. The trap most people fall into is judging by looks: a spent carbon cartridge can appear only lightly tan while it has already stopped adsorbing chlorine and odor, and a sediment filter chokes water pressure across the whole house well before you would think to swap it.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Sediment (spun or pleated) cartridge | Every 3–6 months | Traps grit and rust; clogs first and drops pressure |
| Carbon block cartridge | Every 6–12 months | Removes chlorine taste and odor; capacity-limited |
| Well water or high sediment | Every 1–3 months | Sand and silt load a sediment filter far faster |
| Big-blue housing on city water | Every 6 months | Municipal water is cleaner, so cartridges last longer |
| Pressure has dropped house-wide | Change now | A clogged cartridge chokes flow to every fixture |
| Filter looks fine but time is up | Change on schedule | Carbon stops working long before it looks used up |
The cost of skipping it
What skipping it costs: a clogged sediment cartridge acts like a partly closed valve, dragging pressure down at every shower and tap until the house feels starved. A spent carbon block simply stops removing chlorine taste and odor, so you are paying for filtration you no longer get. Cartridges run $10 to 40 each, a few times a year. Neglect can also let grit reach and wear fixtures; pair filter changes with a yearly pressure check to catch a hidden clog.
How to do it (10 minutes · DIY, spare cartridge on hand)
- Shut the inlet valve feeding the filter housing and open a downstream faucet to bleed off pressure.
- Place a bucket under the housing; there is always some water left in the sump.
- Unscrew the housing with the supplied wrench (turn the clear or blue sump, not the cap).
- Pull the old cartridge, dump the water, and wipe out any grit from the sump.
- Drop in the fresh cartridge, check the O-ring is seated and lightly lubricated, and hand-tighten the housing plus a quarter turn with the wrench.
- Reopen the inlet slowly, check for leaks, and press the pressure-relief button on top if the housing has one.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing whole-house filter changes schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
How do I know when to change my whole-house filter?
Two signals, and time beats looks for both. A drop in water pressure across the whole house is the classic sign a sediment cartridge is clogged. A return of chlorine taste or odor means the carbon has exhausted its capacity, even if the cartridge still looks pale. Since carbon can quit while looking clean, go by the calendar: 3 to 6 months for sediment, 6 to 12 for carbon, and shorter on well water or after a main break stirs up sediment.
What is the difference between a sediment filter and a carbon filter?
A sediment filter is a mechanical screen that traps physical particles: sand, silt, rust, and grit, rated in microns. It protects fixtures and appliances and usually clogs first, so it goes in front. A carbon filter chemically adsorbs chlorine, taste, and odor, and it wears out by capacity rather than clogging. Many whole-house setups run both in series, sediment then carbon, which is why the two cartridges are on different replacement clocks.
Does a whole-house filter reduce water pressure?
A clean, correctly sized filter costs only a couple psi, unnoticeable in daily use. The pressure problem comes from a clogged cartridge or an undersized housing: as the sediment filter loads up, flow chokes and pressure sags at every tap. If you see a house-wide drop, the filter is the first thing to check. Sizing the housing to your flow rate and staying on the change schedule keeps the pressure penalty negligible.