How do I clean or replace a tap aerator?

An aerator is the single most likely cause of poor flow from one tap, and it is the easiest thing in the kitchen to service. It is a stack of fine mesh screens at the end of the spout, it catches everything the pipework sheds, and in a hard water area it scales up steadily until the flow is a dribble or a spray in three directions.

What you'll need

• White vinegar or a limescale remover
• Old toothbrush
• Cloth and pliers, or an adjustable spanner (optional)
• The cache aerator key, if your tap has one (optional)
• Replacement aerator, if needed (optional)

Step by step

1. Block the plughole first.The aerator comes apart into several small parts, at least one of which is a rubber washer that fits nothing else. Put the plug in before you start.
2. Try by hand.Many aerators come off with firm finger pressure, anticlockwise as you look up at it. Warm water on the spout helps if it is stuck.
3. Use a cloth if you need a tool.Wrap the aerator housing in a cloth before gripping it with pliers or a spanner. A tool straight onto chrome leaves marks that are visible forever, and the aerator is at eye level whenever you use the sink.
4. Look for a cache aerator.A smooth ring with no flats and no visible slots is a cache or hidden aerator, removed with a small toothed key that came in the box with the tap and that almost everybody throws away. Keys are available generically — identify the tooth pattern.
5. Lay the parts out in order as they come apart.Housing, rubber washer, flow restrictor if fitted, diffuser, then one to three mesh screens. Photograph them in a row. Reassembling in the wrong order or upside down gives a spray in all directions.
6. Soak everything in white vinegar or a limescale remover.Twenty minutes to an hour for a scaled aerator. Then work the screens gently with an old toothbrush and rinse thoroughly. Hold each screen up to the light — you should see through it evenly.
7. Look for grit as well as scale.Sand, pipe scale and fragments of old washer collect in the aerator, particularly after work on the mains or a burst nearby. That is debris rather than limescale and it simply washes out.
8. Consider removing the flow restrictor.Some aerators contain a small restrictor disc. On a low-pressure system it can be the difference between a usable flow and a trickle, and taking it out is legitimate and reversible. On a mains-pressure system it is saving you water and is worth leaving in.
9. Reassemble and tighten by hand only.Same order, same way up, washer seated flat. Hand tight is enough — a chrome housing crushes easily and a slipping tool marks the spout.
10. Measure properly if you are replacing it.Diameter across the thread, and whether the thread is on the outside of the housing (male, screws into the spout) or inside it (female, screws onto the spout). A 22mm male and a 24mm female look identical in a photograph and neither will fit the other's tap.

Tips

• If flow is poor from one tap only, the aerator is the first thing to check and it takes five minutes. If it is poor from every tap, the problem is upstream and the aerators are innocent.
• Keep the little key that comes with a new tap. Tape it inside the cupboard door under the sink — it is worthless until the day you need it and then it is the only thing that will do.
• A tap that sprays sideways or splits into two streams almost always has a screen assembled the wrong way up or a torn screen, not a fault in the tap.
• Aerators are cheap. If one is corroded, distorted or the screens are torn, replace rather than clean — but measure the thread first.

If it doesn't work

Keeping on top of it

• Unscrew, soak and rinse the aerator (every 6 months in a hard water area)
• Check flow from each tap and compare (occasionally)
• Clean the aerator after any work on the mains supply (as needed)

Questions people ask