Faucets usually leak and wont completely shut off when the valve seat is worn. On older faucets some manufacturers used a compression valve, the more you turn the more you compress the valve and the faucet turns off. Newer faucets come with a ceramic disc valve; this is a much stronger and more affective valve system. If you have an older faucet, it’s not worth trying to repair it since you will ultimately go through the same situation in the future. You may want to consider replacing it with a new unit. Log on to http://www.HomeCenter.com to view a nice selection of faucets. There you will be able to find one that fits your needs.
Replacing a shower faucet is a little more involved then replacing a sink faucet. Consult with a plumbing before removing any components.
The above information is based on opinion, without seeing your faucet it would be hard to accurately diagnose your individual situation.
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Dominic Anfossi
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