A leaking tap wastes water and can produce rust and mineral deposits on your sink and tap. Sometimes you must replace the entire stem assembly in the stem tap to solve the dripping problem. 
Instructions
1、Figure out the type of tap you have so you purchase the correct stem assembly. The compression style has two handles, a ball type has a single handle that pivots, a cartridge can have single or double handles and the disc taps have a single lever.
2、Turn off the water source before you begin to replace the tap stem assembly. Look underneath the sink for the valve, or shut it off on the main valve found near the street or alley.
3、Drain the water from the tap you are working on by turning it to the on position until no water comes out. Use the stopper in the drain or place a towel over it in case additional water runs out while you replace the stem assembly.
4、Find the screw that secures the handle to get to the stem assembly. If a decorative cover hides the screw, use a screwdriver and pry the cover off carefully so you don't scratch or damage any part of the tap.
5、Loosen the stem assembly by turning the nut clockwise. Take the stem assembly out of the tap body.
6、Put the new stem assembly in position and tighten the nut with pliers. Replace the handles, screws and decorative caps, and then properly tighten everything.
7、Test your work by turning on the hot, and then the cold water.
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