Tap aerators: what the WELS stars mean in litres a minute, which thread you have, and the $6 to $16 options at Bunnings

A tap aerator is the little screw-on tip at the end of the spout, and it’s the cheapest water-saving part in the house: a mesh that mixes air into the stream so it doesn’t splash, and a flow regulator that caps the litres per minute. The WELS stars on a tap follow that flow. For a standard spout, the FIX-A-TAP male aerator at Bunnings is the one to buy: 8 L/min, 3 star, with its WELS registration printed on the listing and a WaterMark claim, $8.95 on 1 November 2026. For a mixer with a recessed aerator, the FIX-A-TAP M24 Caché is 6 L/min and 5 star for $10.65. And if your tap has started spitting sideways, the aerator is blocked, and this page covers that too.

What the WELS stars mean in litres a minute

The Water Efficiency Labelling and Standards scheme rates taps and flow controllers in litres per minute, and the label shows both the star rating and the flow. The bands, from the Western Australian Government’s industry bulletin on the scheme: 0 star above 16 L/min, 1 star 12 to 16, 2 star 9 to 12, 3 star 7.5 to 9, 4 star 6 to 7.5, 5 star 4.5 to 6, 6 star under 4. An aerator with a flow regulator sets the tap’s flow, which is why the aerators here carry their own WELS ratings: fit a 6 L/min insert and the tap behaves like a 5 star tap whatever it was sold as.

How much that saves depends on how long the tap runs. A basin tap running while you brush your teeth is the classic case: at 12 L/min it’s a bucket a minute, at 6 L/min half that. The kitchen tap is different, because you mostly fill things, and a slower aerator fills them slower; that’s why we’d put a 5 star aerator on the bathroom basin and a 3 or 4 star on the kitchen sink. WELS estimates the whole scheme saves 209 gigalitres and $1.6 billion on bills in 2025, over $170 for a four-person household, across showers, toilets, washing machines and taps together.

Which tap aerator should you buy?

Start with the thread, then the stars. If the spout has an external thread, you need a female aerator; if the thread is inside the spout, a male one; and if there’s no visible thread and the aerator sits recessed in the spout, it’s a cache aerator that needs a key. Most Australian taps are M22 female or M24 male, and FIX-A-TAP’s male aerator is sold for “13 mm female spouts” by its listing; take the old one to the shop if in doubt.

For a standard tap, the FIX-A-TAP male aerator ($8.95): 8 L/min, 3 star, registration F00611, licence 128, “WELS rated and WaterMark approved” on the listing, which is more paperwork than any other aerator here offers. Its female twin is the same price. The Kinetic small male ($6.25) is 7.5 L/min and 4 star by its listing, with a flow-regulating insert, and the Kinetic standard male ($6.25) is 9 L/min and 3 star with a debris screen; neither Kinetic listing prints a registration number. For a modern mixer, the FIX-A-TAP M24 Caché cascade ($10.65) is 6 L/min and 5 star, registration F00614, and fits M24 hidden aerators including the Estilo pull-out; it needs FIX-A-TAP’s $15.45 cache key set to remove the old one and fit it. The EnduraSeal multi-function swivel ($15.35) is for rinsing the sink: two flow modes on a 360 degree swivel, WaterMark on the listing, but no flow rate or WELS rating, so you don’t know what it saves.

Fixing a spitting or crooked tap

A tap that sprays sideways, spits, or has lost pressure almost always has grit or scale in the aerator mesh. Wrap a cloth around the aerator, unscrew it by hand (anticlockwise looking up at it), and tap the parts out onto a towel: a housing, a mesh or two, a flow disc and a rubber washer. Flush the grit, and if there’s white scale, soak the parts in white vinegar for an hour, rinse and refit in the same order with the washer last. In Adelaide, Perth and on tank or bore water, this is a twice-a-year job; the water softener guide explains why the scale keeps coming back. If the mesh is torn or the housing cracked, replace the whole aerator for $6 to $11, which is also the moment to pick a lower flow.

Aerators and tap filters

A screw-on tap filter such as the Philips X-Guard or the Stefani on-tap unit uses the same thread: it takes the aerator’s place and has its own outlet, so the unfiltered stream runs without the aerator’s flow regulation. Our tap filter guide compares them, and if you want filtered water without losing the mixer’s aerator, a 3 way mixer tap keeps the two streams separate.

The one trap

Buying by picture. Aerators look alike and come in at least four threads (M22 female, M24 male, M21.5 and M24 cache), and the wrong one either won’t start or will seal on two threads and leak. Unscrew the old one first, note whether its thread is inside or outside and whether it needed a key, and buy to match; the $6 Kinetic and the $9 FIX-A-TAP are both cheap enough to get the second one right.

What we left out and why

• FIX-A-TAP female aerator and 13 mm swivel aerators ($8.95 and $13.95 at Bunnings). The female twin of our pick and swivel versions; same flow logic.
• Kinetic 3-piece adaptor kit and FIX-A-TAP cache key set ($11.46 and $15.45). Accessories you may need, not aerators.
• Mondella dual-aerator sink mixers ($98 to $104). Taps with two aerators built in, not replacements.
• Generic aerator multipacks and 24 mm adapter sets on Amazon Australia. No WELS registration on the listings we read, and WELS is the point of the purchase; we’ll add any that print one.
• Kitchen spray-head attachments (Amazon Australia). Swivel sprayers that replace the aerator; useful, but unrated for flow.