So after shutting off the water, remove knob...To remove knob remove screw n center and pull off knob...may be corroded so you may have to wiggle it somewhat. What you will have left is a chromed cover piece and inside of that chromed cover piece is the faucets stem assembly. You will need to remove that chromed cover piece (escutcheon). They usually either thread on or snap on, odds are its threaded so turn it counter clockwise to unthread it.......This piece may also be kind of tight due to corrosion or mineral buildup. Afyter you have that cover peice removed, you should see a round shaft with serations on the end, comes out of either a hex shaped or round shape with two paralell flats on each side piece of brass This is the packing nut or gland nut.. Use a wrench (crescent or other that fits not a pipe wrench or visegrips as they are easy to distort and ruin) and this should be turned CCW as well...Once you unscrew the packing nut turn the center shaft to unthread the stem from the housing and the entire stem assembly can be removed...leave packing nut on the stem itself.....On the end is the washer. Make sure you get a washer that is flat if the washer is suposed to be flat or beveled if it has a bevel on it. While your at it, its best to replace both at the same time, although the hot usually goes before the cold.......To hold the stem from turning when yur trying to remove the screw 9It turns CCW also) that holds the washer inplace use the handle on the end of the stem, and be carefull you do not slip with the screwdriver and run it through your hand.......Don't be surprised if the screw breaks off in the process.....It may be a good idea to replace the screw with a new bras or stainless screw if its corodded up or scarred up from trying to remove it. If the screw breaks its usually cheaper to buy a new stem assembly than pay someone to remove old broken screw... While yu have the stem out, take a flash light an dlook inside the housing assembly the stem screws into and loot at the place the washer seals against. It shold be about 1/2" in diameter with a hole in the middle of it. It should have a shiney contact area on it. PUt your finger in the hole and run your finger nail around that shiney area or look it over very closely and feel for any nicks or burrs. The area is called the seat. Its not uncommon for a faucet that has been leaking to have this seat area erroded or even cracked. If its rough or has a grove in it from erosion, it needs to be replaced. Some faucets have replaceable seats others can be reground, and if noeither of those two options work then a faucet replacement is in order.....Odds are your seat will be good if you did not let it leak for a long time before fixing it......Home Depot or Lowes has a pretty decent selection of repair parts and most towns also have a good plumbing supply house. It woulkd help a lot if you had the brand name of the faucet as well if you go for parts, like new seats or stems.
When you reassemble the faucet, turn the stem so its out all the way just like your turning on the water, before you screw it into the housing, so the stem is not in too far and making contact and cuts the washer when yu tighten up the packing nut....Newer assemblies only have ground washerlesss joints or a simple O ring...some may have packing material, so once yu turn the water on, and before you put that chromed extension back on, look and see if its leaking from around the stem at all...If its a type with packing material just snug up the packing nut a bit more, if the other types leak replace oring. Have fun.......
