Most of the parts that normally break in a kitchen faucet are the internal parts; in fact some of the components are actually engineered to break, for a better reason. Just like the brass or bronze bushing on motor-driven kitchen appliance, they are engineered to wear first to avoid it from damaging the far more expensive shafting. In kitchen faucets, to maintain the main casing, the stem is crafted with a softer material such as brass. As we open and close the faucet, the brass stem slowly wears, little by little, till the entire tread then finally vanish and can no longer apply pressure to the rubber seal regardless of how much you turn it. When this happen, a leak appears, and to resolve it, the stem is required to be replaced with a brand new one. Normally you can find a replacement faucet stem at a very low price tag, just about less than $10, much cheaper than if you are going to purchase the entire faucet.