Most kitchen sinks are equipped with a faucet aerator that screws onto the end of the faucet, adds air to the water and screens out debris. The screen inside the aerator collects the debris that occasionally needs to be cleaned. To do this, unscrew the aerator and rinse out as much debris as possible under a running faucet. You can use a small brush to scrub it a bit. If you have lime or water deposits, let the aerator soak in pure vinegar for an hour or so, and then rinse. Commercial lime removal products are also good for this process.