Although filter brands and models may vary from pool to pool, one of the most common ones we install is this Hayward C1200 Star-Clear Plus Filter.
You will usually find the cartridge filter as part of a system of equipment we install to handle all of the workings for your pool, as shown in the diagram below:
The first thing you have to do is open the outer casing, so you can access the cartridge filter inside. Turn the butterfly nut at the top of the case counterclockwise to loosen it, and then lift off the entire filter head cover (see part 5 in the diagram).
Remove the cartridge filter, but be sure not to misplace any of the parts you remove in order to get it out of the casing and you may want to print out the above drawing to use as a guide when you want to put it back together again. Use a regular garden hose to clean the filter with running water and then reinstall it.
When you've finished reassembling the casing, make a note of the pressure reading on the gauge. When the pressure has increased 10 psi above the noted amount, it will be time to clean the filter again, so be sure to check the gauge at least once a week.