What is a faucet aerator?
Updated August 2026
An aerator is the small screened insert threaded into the tip of a faucet spout that blends air into the water so the stream lands soft, straight, and splash-free. Behind the visible screen sit a rubber washer, a flow restrictor disc, and one or two mesh layers. Federal rules cap new faucets at 2.2 gallons per minute, WaterSense-labeled models run 1.5, and several states now set 1.2 gpm for bathroom faucets.
Where it is
Check the very end of the spout. Most aerators today are recessed and show only a ring of knurling or a flat face with key slots; older ones stand slightly proud with wrench flats. Nearly all of them unscrew counterclockwise as seen from below, which feels backward until you remember you are working from underneath. Cache-style units need the plastic key that came with the faucet, usually taped inside the vanity cabinet or sold for $3–6 at any hardware store. Threads run 15/16 inch male and 55/64 inch female on kitchen faucets and 3/4 inch on many bathroom models, so bring the old part to the store.
What it does
Two jobs, one part. Mixing air into the stream stops water from spraying off the bottom of a bowl or a dinner plate, and the restrictor disc holds flow to the rated gallons per minute, trimming hot water use without the sad feel of a starved shower head. The failure creeps. Calcium and grit build on the intake side of the mesh, and flow at that one fixture falls 30 to 50 percent across a year or two while every other tap behaves normally, so owners blame the water heater, the shutoff, or the city. A cleaner test: if one faucet is weak and the rest are strong, the trouble is in the last inch of the spout. A split stream, a sideways jet, or sand in the basin after a street main repair all point the same direction.
Maintenance
Unscrew and rinse the aerator every 6 months in a hard-water house, once a year elsewhere, and right after any work on the street main (aerator cleaning intervals). The routine takes 5 minutes: close the drain stopper so nothing small vanishes, twist the aerator off by hand or with rag-wrapped pliers, lay the parts out in order, soak them in white vinegar for 20 to 30 minutes when scale is heavy, brush the mesh with an old toothbrush, and reassemble finger-tight plus an eighth of a turn. Torn screen or flattened washer means a new unit rather than a rescue. The faucet checklist covers the rest of the fixture, faucet lifespans explain when cleaning stops being the answer, and the cost of a dripping faucet covers the leak you have been tolerating.
What it costs to replace
A replacement faucet aerator runs $3–10 for a standard aerator, $10–20 for a cache-style or swivel model, and no labor if it turns by hand.
OnOtto's photo scan identifies parts like this in your home and builds the maintenance schedule for you. See how the scan works.
Frequently asked questions
Which way do I turn an aerator to remove it?
Counterclockwise viewed from below, which looks like clockwise while you stare up at the spout from the sink. Try fingers first, since scale usually surrenders to steady pressure. If it refuses, wrap the flats in a rag or masking tape and use slip-joint pliers gently, or soak a paper towel in white vinegar and rubber-band it around the tip for an hour to soften the deposits.
Will a low-flow aerator make the water feel weak?
Rarely, because an aerator changes volume rather than pressure. A 1.5 gpm insert in a bathroom faucet feels almost identical to a 2.2 gpm one for hand washing and saves a household thousands of gallons a year. Filling a stockpot is where the difference registers, which is the argument for a laminar or higher-flow insert on the kitchen faucet and the low-flow versions on bathroom sinks.
One faucet is slow and the rest are fine. What now?
Start at the aerator, since checking it is free and it is the answer most of the time. If a clean aerator changes nothing, isolate the side: run only hot, then only cold. Weak on one side points at the angle stop under the sink, partly closed or crusted. Weak on both with a clean aerator points at the cartridge or a plugged inlet screen inside the valve body.