Do i presume right, with you asking this question, that you dont have the manual for this filter?
If not, here are a couple of blocks from the manual you get when you buy it..
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Magnum media is serviced:
1. Shut down system and remove Canister.
2. Change media:
CARBON/MEDIA CONTAINER
Remove media and rinse container thoroughly. Refill container
with Black Diamond Activated Carbon and rinse carbon
thoroughly. Rinse or replace Rite-Size Filter Sleeve.
Environmental Tip...Used activated carbon can be added to garden soil to aid
in plant fertilization (does not apply to media used with fish medications).
MICRON CARTRIDGE
Remove and clean Cartridge – never brush or machine wash.
Rinse off all visible dirt. Mix a solution of one part chlorine
bleach to three parts water. Immerse cartridge completely in
solution and soak overnight. Rinse thoroughly until chlorine
smell disappears.
For Best Results...Purchase a second Micron Cartridge for alternate use while
original Cartridge soaks and dries thoroughly.
3. Clean Canister thoroughly, especially sump area.
4. Clean Impeller Assembly and inspect for wear and smooth
rotation. If excess wear is noted, replace worn parts immediately.
6. Gently clean flat Rubber Gaskets with warm water only.
7. Wash O-Ring Seating Area on Canister and Cover.Wet O-Ring
before reinstalling.
8. Reassemble system and return to operation as previously instructed.
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Keep valves clean at all times.
Periodically remove Coupling Barrel to clean
Coupling grooves and O-Rings (Figure 23).
Inspect O-Rings for wear. To replace,
request part #PR1450.
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Between that and johansonp's comments, you should be on the right track...
Niko