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How do you change a whole-house water filter cartridge?

Updated August 2026

15–20 minutes · Easy DIY

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Swapping a whole-house cartridge is a 15 to 20 minute job you repeat every 3 to 6 months: close the inlet or bypass valve, press the pressure-relief button on the housing, unscrew the sump, and drop in a fresh filter. Cartridges run $10 to $40. The step that separates a clean change from a wet basement is greasing the big O-ring before the sump goes back on, and it takes about ten seconds. A cartridge left in too long does more than stop filtering: it chokes flow to every fixture in the house.

What you need

Before you start: Pressurized water behind a threaded plastic sump deserves respect. Bleed the line and press the relief button before the wrench touches the housing, and know where your main shutoff is in case the bypass valve does not hold. If a UV lamp shares the line, switch its power off first: the lamp runs hot, the quartz sleeve breaks easily, and the ballast is live. Do not drink from the taps until the new cartridge has flushed for 3 to 5 minutes, and sanitize the sump after any boil notice.

Steps

  1. Buy the cartridge before you open anything. Slim housings take a 10 inch cartridge about 2.5 inches across; big blue housings take 4.5 inch cartridges in 10 or 20 inch lengths.
  2. Copy the micron rating off the old cartridge. Five micron is typical for sediment, and going finer than the system was sized for costs you pressure at every tap.
  3. Close the bypass or the inlet valve on the housing. If the system has neither, close the main shutoff instead.
  4. Open a cold tap downstream and let it run until it stops, which bleeds the pressure out of the line.
  5. Press the red pressure-relief button on top of the housing until the hissing stops. Skipping this is how people end up wearing the sump.
  6. Set a bucket and towels underneath, fit the housing wrench over the sump, and turn. A big blue sump holds close to a gallon of water.
  7. Dump the old cartridge and wipe the sump out. If the system feeds drinking water, sanitize it with a tablespoon of unscented bleach in a gallon of water, then rinse thoroughly.
  8. Lift the large O-ring out of its groove, wipe the groove clean, coat the ring with food-grade silicone grease, and seat it flat all the way around. This one step prevents most leaks.
  9. Drop the new cartridge in, thread the sump on by hand so it cannot cross-thread, and snug it with the wrench. Open the inlet a quarter turn and watch the seam before opening fully, then run a cold tap 3 to 5 minutes and write the date on the housing.

Or hire it out

A plumber charges $100 to $175 to change a whole-house cartridge, roughly a full year of DIY changes in one visit. The only tool required is the plastic wrench that shipped with the housing.

Done. Now the part everyone skips: doing it again on schedule. Log it in OnOtto and the next reminder for water filter changes sets itself.

Log this task, get the next reminder

Frequently asked questions

How do I know it is time before the calendar says so?

Pressure is the honest indicator. When the top-floor shower goes noticeably weak and every other fixture is fine, the cartridge is loading up. A pressure gauge on the hose bib makes it obvious: most homes sit at 45 to 60 psi, and a filter that has dropped you 10 psi or more is finished. The cartridge itself tells the same story, going brown or gray on the inlet side. Taste and odor returning means a carbon block is spent. Intervals by water type are on how often to replace a whole-house water filter.

Do I need sediment, carbon, or both?

Sediment first, always. It catches sand, rust flakes, and silt that would otherwise wear out valve seats, faucet cartridges, and the water heater. Carbon comes second, for chlorine taste and odor, and it clogs fast if it has to do the sediment stage job too. Two-stage housings run about $10 to $40 per cartridge. Point-of-use gear is on its own clock: see reverse osmosis filter intervals and UV bulb intervals.

The housing leaks after the change. What went wrong?

The O-ring, in nearly every case: pinched out of the groove, dry, twisted, or accidentally left stuck in the cap. Depressurize, take the sump off, and reseat a clean, greased ring rather than tightening harder. Replace the O-ring itself once a year for $3 to $8. Over-tightening cracks the sump, and a cracked housing is a $30 to $80 replacement plus whatever the water reached. Housings and heads themselves age out too: see how long a water filtration system lasts.

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