What you need before you start

Before you remove the old cartridge, gather the items you will need: a replacement cartridge that matches your filter model, a bucket or large bowl to catch water, a wrench or filter wrench if your system uses one, and clean towels or rags. Check your filter's manual or the label on the housing to find the exact cartridge model number — buying the wrong size wastes money and leaves you unprotected.

Turn off the water supply to your filter system. Most systems have a shut-off valve on the incoming water line; turn it clockwise until it stops. If you cannot find a shut-off valve, you may need to turn off the main water supply to your home. Wait a few minutes for pressure to drop inside the housing.

Place your bucket underneath the filter housing before you open it. Even with the water off, some water will spill when you remove the old cartridge — this is normal and expected.

Key Takeaways

  • Turn off the water supply and place a bucket under the filter housing before opening it, because water will spill regardless of how much pressure you released.
  • The cartridge model number is printed on your old cartridge or in your system manual; buying the wrong size means the filter will not work.
  • Most cartridges unscrew by hand or with a filter wrench; if you force it, you risk cracking the housing and creating a leak.
  • Rinse the inside of the housing with clean water before inserting the new cartridge to remove sediment and debris.
  • After reassembly, turn the water back on slowly and check all connections for leaks before you leave the area.

Removing the old cartridge

Open the filter housing by unscrewing the bowl or cap at the bottom. Most housings have a large plastic nut that turns counterclockwise by hand; if it is too tight, use a filter wrench or an adjustable wrench to loosen it. Turn slowly and steadily — if you feel sudden resistance, stop and check that you are turning the right direction.

Once the housing is open, lift out the old cartridge. It may stick slightly; gently wiggle it side to side as you pull. Do not force it or you may crack the plastic housing. The cartridge will be wet and may drip, so keep your bucket underneath.

Look inside the housing at the bottom. You will see a rubber seal or gasket. Leave it in place unless your manual says to replace it. Inspect it for cracks or damage; if it looks damaged, order a replacement gasket along with your next cartridge.

Cleaning the housing before installing the new cartridge

While the housing is open, rinse the inside with clean water from a pitcher or hose. This removes sediment, debris, and old filter material that can reduce the new cartridge's performance. Pour water slowly so it drains into your bucket.

Wipe the inside walls with a clean cloth or paper towel. Pay attention to the bottom where sediment collects. Do not use soap or chemicals — water only.

Installing the new cartridge

Remove the new cartridge from its packaging. Some cartridges come with protective plastic caps on the ends; remove these before installation. Check that the cartridge height matches the space inside the housing — it should fit snugly without forcing.

Insert the new cartridge straight down into the housing. It should slide in smoothly. If it does not, stop and check that you have the right model and that nothing is blocking the opening.

Screw the housing bowl or cap back on by hand first, turning clockwise. Once it is hand-tight, use your wrench to tighten it another quarter to half turn. Do not over-tighten — this can crack the housing or damage the seal.

Turning the water back on and checking for leaks

Open the water shut-off valve slowly by turning it counterclockwise. Open it gradually over 10 to 15 seconds rather than all at once; this prevents pressure shock that can damage the new cartridge or connections.

Watch the housing and all connection points for leaks. Water should flow smoothly through the system with no drips at the seams. If you see a leak at the housing cap, turn the water off, tighten the cap slightly more with your wrench, and turn the water back on.

Let the water run through the system for 30 seconds to flush out any loose material from the new cartridge. Some systems produce slightly cloudy water for the first few minutes — this is normal and will clear.

When to replace your cartridge

Most cartridges last between three and six months, depending on your water quality and how much water your household uses. Check your manual for the recommended replacement schedule. Some systems have a pressure gauge that shows when the cartridge is clogged; if the gauge reads high, it is time to replace it.

Mark your calendar when you install a new cartridge so you remember when to replace it next. Waiting too long reduces water flow and defeats the purpose of the filter.

Frequently Asked Questions

What do I do if the old cartridge is stuck and won't unscrew?

Stop forcing it immediately — you risk cracking the housing. Wrap a towel around the nut for better grip and try again with steady pressure. If it still will not budge, let it sit for 15 minutes; sometimes mineral deposits loosen on their own. If it remains stuck after that, contact the filter manufacturer for advice before proceeding.

Can I reuse the old cartridge or clean it instead of replacing it?

Most cartridges cannot be effectively cleaned and reused. Once saturated with contaminants, they lose their filtering ability. Rinsing does not restore them. Buy a new cartridge each time — the cost is small compared to the protection it provides.

Why is water leaking from the housing cap after I installed the new cartridge?

The rubber gasket may not be seated properly, or the cap may not be tight enough. Turn off the water, unscrew the cap, check that the gasket is centered and not twisted, and reinstall it. Tighten slightly more than before, but do not force it.

How do I know if I bought the right cartridge model?

The model number on the new cartridge must match the number on your old cartridge or in your system manual. Check before you leave the store or open the package. If the numbers do not match, return it and order the correct one.

What should I do with the old cartridge after I remove it?

Most cartridges can be thrown in the regular trash. Some communities have recycling programs for filter cartridges; check with your local waste management. Do not pour the cartridge contents down the drain or bury them.