A sink or faucet aerator sometimes gets clogged which slows the flow of water. This happens to due to the minerals in the water that start to block the holes of the faucet aerators. If you have hard water in your home, then this can be a frequent occurrence, but the solution is simple; just switch out the filter assembly with a new one. The replacement water faucet aerators are cheap and easy to install. They are often sold in sets with the metal or plastic screw on portion that attaches to the spout. The sizes vary by type and brand like those from Moen, Kohler, Delta and other top kitchen and bathroom companies. If you notice the water pressure and flow of your bathroom or kitchen sink slowing down over time (and you don't have a low flow model installed), you probably have to change out the faucet aerator.