One of the most common parts to clog in any faucet is the aerator. The aerator screws onto the end of the faucet, and it has a small, round mesh screen that introduces air into the water flow from the spout. Debris collects on this screen, blocking water flow substantially in some cases. This reduces water flow, but it is easy to fix. All you need to do is unscrew the aerator, clean out the debris and screw it back onto the end of the spout.
When the cartridge clogs, it is more difficult to fix. The cartridge is the part inside of the faucet that regulates the water flow and temperature. Sediments and debris collect inside the small inlet holes in the cartridge, causing the holes to shrink. This reduces your faucet's water flow and makes it appear like the water pressure is dropping. An easy fix solves this problem: Just take off the faucet's handle with an Allen head wrench, unscrew the bonnet nut and remove the cartridge. Either rinse off the cartridge or replace it with a brand new cartridge.
Ball Lever Faucet Clogs
Older faucets use a ball lever instead of a cartridge to control water flow and temperature. When these faucets clog, there is sediment or dirt inside the seats and springs, which also reside inside the faucet body. The good news is the faucet repair is much the same way as for a cartridge faucet. All you need to do is remove the set screw in the handle with a screwdriver or Allen wrench, pull off the handle, unscrew the dome cap under the handle and take off the cam and packing. The ball lever is all that remains. Take the ball lever out of the faucet, remove the rubber seats inside the faucet then clean out the inlet holes to remove any debris caught inside. A small brush or pipe cleaner is ideal for cleaning these holes.
Faucet Line Clogs
If your faucet water lines clog with debris, it is a good idea to call a plumber or professional. These lines are difficult to unclog by traditional means, and the clog may be anywhere. If you try all of the other solutions and still experience low water pressure, consider removing the supply hoses and flushing them out. Before you remove the hoses, turn off the water by shutting the valves on the water pipes. After you unscrew the supply lines, use a pipe cleaner or water to flush out the debris before you reattach them and test the faucet.