Changing a Moen single handle sink faucet cartridge in many cases is quite easy though hard water conditions can make it very difficult. There is typically a cover on the knob or lever that when it is pried off with a knife-edge exposes a Phillips Screw underneath. Once the handle is of there is a stop tube or, retainer nut that has to be removed to expose the retaining clip. Finding a parts diagram for your faucet can be very helpful in taking it apart. Once the retaining clip has been removed you are now ready to remove the cartridge. You will need a Moen cartridge removal tool to pull out the cartridge. My preference for the tool is a Pasco Specialty and Mfg. Inc. Moen Stem & Cartridge Puller part # 7040. There are many other tools available as well. The key to removing a Moen cartridge is to get the cartridge loose first by turning the cartridge. The Moen cartridge is inside a bore and has two ears the tool locks into. Once the cartridge is spinning freely the Pasco puller tool has a thumbscrew which screws into the center of the stem where the handle screwed in. Simply screw the thumbscrew in then use the puller as a handle pull the cartridge straight out. Most of the time the cartridge comes right out. Sometimes the center stem pulls out leaving the cartridge behind. The Pasco Puller has a section where there is a rod with a locking button on it. Pressing the button and inserting it into the cartridge then having the button pop out into one of the holes in the cartridge will lock the tool into the cartridge permanently until the cartridge come out. If the cartridge doesn’t come out with this method both the puller and the tool are lost. I would only use this side of the tool if the cartridge was moving freely and the center stem pulled out with almost no effort. Once the stem is out inspect the bore where the cartridge was and make sure there are no bits of rubber from the old cartridge you are now ready to insert the new cartridge.
The Moen part # 1225 plastic cartridge and the #1200 brass cartridge are interchangeable with plastic being the better choice in hard water conditions. Use a silicone based (non-petroleum) plumber’s grease to lubricate the rubber seals and o-rings on the cartridge then insert the cartridge into the bore and replace the retaining ring and stop tube or retainer nut. Put the handle on, turn the water supply back on, and test the faucet for proper operation. If the turning of the handle for hot and cold is reversed then take the handle back off. Turn the center stem of the cartridge 180-degrees and put the handle back on. The handle direction for hot and cold selection should now be correct.