Faucet Aerator: What It Is, Types, Sizes & How to Choose the Right One

In short: a faucet aerator (called a tap aerator in the UK) is the small screwed-on piece at the tip of your faucet that mixes air into the water, so you keep the same feel of flow while using up to 50% less water. T

o choose or replace one, or to fit a water filter, the only thing that really matters is the thread: whether it's male (M) or female (F) and its diameter (usually M22–M24). 

Here's everything you need, plus how to check yours in 30 seconds.

What is a faucet aerator (and what each part is called) 

The aerator, also called the spout tip, the screen, or simply "the thing on the end of the faucet", is the piece fitted into the water outlet. Inside it has a mesh/screen and a chamber that pulls air into the stream. 

The result: a softer, splash-free flow that feels full but uses less water.

It's the part you unscrew to clean out limescale… and the part you remove or adapt when you want to install a water filter on your tap.

What it's for: saving water and comfort 

• Water saving: up to 50% less water (and lower bills) with no change in comfort (verify figure). 
• Less splashing: a smoother, more even stream.
• Nicer flow: the air gives the water more "body". 

Types of aerators 

• Standard: the most common, screwed onto the spout tip. 
• Swivel (ball-joint): lets you aim the stream.
• Start-stop: opens/closes the flow with one click, without touching the handle. 
• Flexible / pull-out: with a flexible spout, typical in kitchens. 
• Small-diameter: for taps smaller than standard. 
• For taps with no thread: these include an adapter so you can still fit them (same principle we use to fit a filter — see below). 

What really matters: the thread 

Before buying an aerator — or a filter — check two things about your faucet:

• Male or female thread?
  • Male (M): the thread is on the outside of the spout (the aerator screws in inside). Marked "M" + diameter. 
  • Female (F): the thread is on the inside of the spout (the aerator screws on outside). Marked "F" (or H) + diameter.

• What diameter? The most common standard sizes:

How to check your faucet thread in 30 seconds 

1. Unscrew the current aerator (by hand, or with a multi-tool, turning toward you). 
2. See where the thread is: on the outside of the piece (male) or inside (female)? 
3. Measure the diameter with a ruler or, better, calipers — it usually falls between 18 and 24 mm. 
4. No tools? Take the old aerator to the store as a reference, or compare it to a coin to estimate. 

Want to fit a water filter on your tap? 

This is where the adapter comes in. A tap water filter installs exactly where the aerator sits — on the spout thread. So compatibility depends on the same things (male/female and diameter), and that's why you sometimes need an adapter.

• If your faucet has a standard thread, the filter usually screws on directly.
•  If your faucet has an unusual, hidden, or no thread (designer taps), an adapter bridges the gap so the filter still fits. 

The EcoPro by Tappwater installs in seconds onto your faucet thread and is ready for the most common standard threads; for everything else there are the adapters that cover the uncommon sizes (verify exact thread list). That turns almost any tap into filtered water — no tools, no plumber. Browse all faucet water filters.

How to install or replace an aerator (or a filter)

1. Unscrew the old aerator (by hand; if stuck, use a multi-tool with a cloth to avoid scratches). 
2. Clean limescale off the spout thread. 
3. Check the rubber washer. 
4. Screw on the new aerator — or the filter/adapter — hand-tight, without forcing. A quarter-turn more if it drips. 

No plumber needed.

Maintenance: goodbye limescale 

Over time, aerators collect limescale and grit that cut the flow. To clean: unscrew it, soak it in vinegar for a few hours, brush the mesh and rinse. If it's badly worn, replace it. If you live in a hard-water area, limescale is a recurring problem — a filter not only improves your drinking water, it also helps your fittings last longer.

Some frequently asked questions:

What does a faucet aerator do? 

It mixes air into the water so you keep the feel of full flow while using up to 50% less, and it reduces splashing.

How do I know which faucet aerator I need? 

Check two things on your tap: whether the thread is male (M) or female (F), and its diameter (usually 18–24 mm). Those two facts are enough.

What sizes do faucet aerators come in? 

The most common are M24 and M22 (male) and F22/F24 (female), plus small (M18/M20) and large (M28).

What is the thing on the end of a faucet called?

The aerator (also "atomizer" or "spout tip") — the screwed-on piece at the water outlet.

Can I fit a water filter if my tap has no thread or an unusual one? 

Yes. An adapter bridges your tap and the filter, so you can install it even when the thread is uncommon or hidden.