TL;DR
When a single faucet loses pressure and the rest of the house is fine, the aerator is the culprit about nine times out of ten. Unscrew it, soak the parts in white vinegar for twenty to sixty minutes, brush out the grit, and reassemble in the same order. The whole job takes ten minutes and costs almost nothing.
What an aerator is and why it clogs
The aerator is the small screened cap on the end of a faucet spout. It mixes air into the water stream, which is why the flow looks white and soft instead of like a hard jet. It also catches debris.
Two things clog it. The first is mineral scale, mostly calcium and magnesium left behind as water evaporates in the screen. The second is grit -- sand, sediment, and small flakes of pipe scale that travel through the plumbing and get caught.
Grit often shows up right after work is done on the water line, or after the municipal supply is shut off and turned back on. Scale builds gradually, which is why the pressure drop sneaks up on you.
How do I know the aerator is the problem?
Check whether the problem is limited to one faucet. If other taps in the house have normal pressure, the restriction is at that fixture. Then test hot and cold separately by running each alone. If both are weak, the aerator is the likely cause, and it is the cheapest thing to rule out first.
Removing the aerator
Most aerators unscrew by hand. Close the drain first or put a towel over it, because small parts fall and vanish immediately.
Grip the aerator and turn it counterclockwise as you face up at it. If it will not budge, wrap the housing in a cloth or a strip of tape to protect the finish, then use slip-joint pliers with light pressure. Do not crush it.
Stubborn ones are usually scaled in place. Wrap a vinegar-soaked paper towel around the joint, secure it with a rubber band, and leave it thirty minutes before trying again.
Some modern faucets have a hidden or cache aerator that sits recessed inside the spout. Those need a small plastic key, usually included with the faucet, that slots into notches in the aerator face. If you do not have the key, most home centers carry a universal version.
Taking it apart and soaking it
Lay the parts out on a towel in the exact order they came out. A typical aerator has an outer housing, a rubber or plastic washer, a flow restrictor disc, and one or more mesh screens. Photograph the stack before you separate it if there is any doubt.
Rinse each piece under running water first, screen side down, to flush out loose grit.
Then soak everything in a small cup of undiluted white vinegar. Twenty minutes handles light scale, and an hour handles a badly crusted screen. The vinegar dissolves the calcium deposits the same way it works when descaling an electric kettle.
Never mix vinegar with bleach or with any other cleaner. That combination releases chlorine gas. One product, in one cup, and nothing else.
Source: plumbing fixture manufacturer maintenance guidance
Scrubbing and reassembly
Brush each part with an old toothbrush, working the bristles through the mesh from both sides. A straight pin or a needle clears individual blocked holes in a plastic disc.
Rinse everything in clean water. Hold the screens up to a light -- you should see light through every hole.
Before you reinstall, run the faucet on full for fifteen seconds with the aerator off. That flushes any debris sitting in the spout, so you do not immediately clog the screen you just cleaned. Expect it to spray, so hold a cloth over the opening.
Reassemble in the same order, seat the washer properly, and screw the aerator back on hand tight. Overtightening cracks plastic housings and distorts the washer. Run the water and check for drips around the threads; a small leak usually means the washer is pinched or missing.
When cleaning the aerator does not fix it
If flow is still weak, work back up the line. The angle stop valves under the sink may be partly closed, or scaled internally. A cartridge inside a single-handle faucet can clog with the same grit that filled the aerator. Supply lines with an integral screen can also block.
If pressure is low throughout the house, the aerator was never the issue. That points to a pressure regulator, a main valve, or the supply itself, and it is a plumber's call.
Discolored water, a sudden change in taste, or grit at every fixture at once also warrants a call rather than a screen cleaning. Plumbing repair is a separate trade from cleaning, and it is worth treating it that way.
Preventing the next clog
Clean the aerator every six to twelve months as routine maintenance, and immediately after any plumbing work in the house or the street.
Wipe the faucet dry after use in a hard water area. The scale that crusts the outside of the spout is the same deposit building inside, and the approach in removing hard water stains applies to both.
While you have the sink area open, it is a natural time for stainless sink care and a look at why a kitchen drain smells, since both are five-minute jobs that get skipped for years.
FAQ
Which way do I unscrew a faucet aerator?
Counterclockwise as you look up at the end of the spout, which feels like clockwise if you are looking down from above. Protect the finish with a cloth if you need pliers, and turn slowly. Some aerators are reverse-threaded, so if it tightens noticeably, stop and try the other direction.
How long should I soak an aerator in vinegar?
Twenty minutes for light mineral haze and up to an hour for heavy crust. If deposits remain after an hour, soak longer rather than scraping with metal, which damages the mesh. Rinse thoroughly afterward so no vinegar taste or smell carries into the water.
Can I clean an aerator without removing it?
Partly. Fill a small bag with white vinegar, slip it over the spout, and secure it with a rubber band so the aerator is submerged, then leave it thirty to sixty minutes. It dissolves scale but does not remove trapped grit, so it is a maintenance step rather than a fix for a clog.
What if the aerator is stuck and will not turn?
Wrap a vinegar-soaked paper towel around the joint for thirty minutes to soften the scale, then try again with cloth-protected pliers. Steady pressure works better than sudden force. If the housing starts to deform, stop -- replacement aerators are inexpensive and widely available.
Should I remove the flow restrictor to get more pressure?
Removing it does increase flow, but it also increases water use and may conflict with local plumbing requirements. It is better to clean the restrictor properly, since a clogged one behaves like a much smaller opening than it was designed to be.
How often should faucet aerators be cleaned?
Every six to twelve months in most homes, and more often in hard water areas. Also clean them any time water service is interrupted and restored, because that is when sediment gets shaken loose in the pipes and carried into the screens.
The whole-house equivalent of this routine is covered by house cleaning services.
Small maintenance jobs like this one are easy to postpone until the whole kitchen needs attention at once. If you would rather have it kept up on a schedule, every home is different, so the real number depends on size, condition, and what you want covered. Get a quote and we will walk you through it.