Fix low water pressure at one faucet
When one faucet has weak flow but the others are fine, check the aerator at the tip of the spout first. That small screen catches grit and mineral scale. Unscrewing it, cleaning or soaking it, and screwing it back on often brings the pressure right back. Wrap the aerator in a bit of tape before you grip it with pliers, since chrome finishes scratch easily.
What the aerator does
The aerator mixes air into the water and limits the flow. Its screens are fine enough to catch sand, bits of pipe scale and rubber, especially after plumbing work or a water main repair nearby. A clogged aerator gives a weak or sputtering stream, or one that sprays off to the side.
If the flow is still weak with the aerator off, the problem is further back: a under the sink that isn't fully open, a clogged cartridge, or a kinked supply line.
What slows one faucet
Grit and mineral scale in the screen.
The valves under the sink are sometimes left partly closed after work.
Debris lodged inside the faucet.
A flexible line bent under the sink.
| What you notice | Likely cause | What to check |
|---|---|---|
| One faucet, both hot and cold | Clogged aerator | Clean the aerator. |
| One faucet, hot side only | Hot-side valve or supply | Check the valve under the sink. |
| Every faucet in the house | Main valve, pressure regulator or supply | Check the ; call a plumber. |
| Weak with the aerator off | Valve, cartridge or supply line | Open the valves; check the cartridge. |
Clean the aerator, step by step
- Plug the drainClose the stopper or lay a towel in the sink so small parts can't fall down the drain.
- Unscrew the aeratorUnscrew it by hand, turning it counterclockwise as you look up at it from below. If it's stuck, wrap it in tape or a rag and turn it gently with pliers. Hidden aerators that sit inside the spout need the small key that came with the faucet.
- Clean the screensTake the parts out in order and lay them in a line so you know how they go back. Rinse out the grit, scrub with a toothbrush, and soak crusty parts in vinegar for about 30 minutes.
- Flush the lineWith the aerator off, run the faucet for a few seconds on hot and cold to flush out any loose debris. Keep the sink stopper closed so no small parts slip down the drain; a few seconds is plenty.
- Reassemble and testPut the parts back in the same order, screw the aerator on hand-tight, and run the water. The stream should be full and steady.
Watch it done
- The stream comes out full and steady
- No grit left in the aerator screens
- The aerator is hand-tight and doesn't drip at the threads
Still weak? Check that both shutoff valves under the sink are fully open.
If it's weak with the aerator off
Make sure both shutoff valves under the sink are fully open. On a quarter-turn valve, the handle should line up with the pipe. On an older round-handle valve, open it all the way, then back it off slightly, and don't force a stiff old valve; it can start leaking at the stem.
If only the hot side is weak, the problem may be the hot supply or the water heater. If the faucet has a cartridge, debris may be stuck inside it; our dripping faucet guide shows how to take it out.
What a pro typically charges (a rough estimate; prices vary by area): A plumber typically charges $125–$300 to track down low pressure at a fixture.
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