Faucets have an aerator built into the spigot to help prevent water spray and cloudiness when you use the faucet. Aerators are essentially metal screens placed inside an aerator cap. The screens have a tight weave and eventually clog up with sediment. When this happens, you need to replace the aerator to increase the flow of water out of the faucet. To replace the aerator, you need to measure it so you know what size to purchase for your faucet.
Grip the aerator cap, which is located on the tip of the faucet's spigot, with a pair of pliers.
Turn the aerator cap counterclockwise with the pliers to unthread it from the faucet's spigot.
Push the screen out of the aerator cap. Separate the screen from the small piece of filter material if necessary.
Measure the diameter of the aerator screen, using a pair of veneer calipers. Write down this measurement.