Quick Answer:
This is almost always a clogged aerator or spray plate. When the screen or internal threads are blocked, the faucet flows freely with the aerator removed but becomes weak once the aerator is reinstalled. If you recently added a filter and the problem started then, check Low pressure after installing water filter for related causes.
Why This Happens
Mineral deposits, sand, pipe scale or tiny particles from a recent repair can get trapped inside the aerator’s screen or the threads that hold it. The small holes in the aerator concentrate the water flow, so even a little clog greatly reduces visible flow. Pull-down sprayers have a spray plate with many small holes that clog the same way; a stuck check-valve inside the spray head can also reduce flow. If the restricted flow makes the faucet sing or whistle, see One faucet whistles under low pressure.
Step-by-Step What to Do
1. Remove the aerator
- Grip the aerator housing with your hand or wrap it with a cloth to protect the finish. Unscrew it counterclockwise. If it’s tight, use adjustable pliers with a rag between the jaws to avoid scratches.
- Note any small parts: the screen, flow restrictor, and rubber washer; keep them in order for reassembly.
2. Soak in vinegar
- Place the disassembled aerator parts in a small cup of white vinegar for 30–60 minutes to dissolve mineral buildup.
- For heavy scale, you can leave them longer (a few hours), but check occasionally so plastic parts don’t degrade.
3. Brush and rinse debris
- Use an old toothbrush or small soft brush to scrub the screen, flow straightener, and housing. Remove any visible debris from threads and cavities.
- Rinse parts under running water to wash out loosened particles.
4. Run the faucet without the aerator to flush
- Turn the faucet on full for 20–60 seconds with the aerator removed to flush loose debris from the spout and supply lines.
- If particles come out, keep flushing until the water runs clear.
5. Reinstall and test
- Reassemble the aerator parts in the original order, screw it back on by hand, then snug with pliers using a rag. Turn the faucet on and check flow and spray pattern.
- If flow is restored, the problem was the aerator. If not, proceed to the next step.
6. If you have a pull-down sprayer, clean the spray plate and check check-valves
- Remove the spray head per the manufacturer’s instructions. Soak the spray plate in vinegar and brush the holes.
- Inspect the internal check-valve(s) and the diverter for blockages or mineral buildup. Clean and test the check-valves; replace them if they are damaged or stuck.
What Not to Do
- Don’t clean only the outside—debris inside the aerator threads and screen is the real culprit.
- Don’t use a wire file or sharp metal to poke the screen; that can enlarge holes or damage parts.
- Avoid pouring bleach or strong acids into the aerator housing; these can harm rubber parts and finishes.
When to Call a Professional
- If the flow is still weak with the aerator removed — that points to a supply problem, valve issue, or blockage inside the fixture.
- If multiple fixtures show similar low flow, you may have a broader plumbing or pressure issue that needs diagnosis.
- If the spray head’s internal parts are broken or a check-valve needs replacement and you’re not comfortable doing it, call a plumber.
Safety Notes
- Use gloves if you have sensitive skin before handling vinegar or cleaning agents.
- Protect faucet finishes with a rag when using pliers to avoid scratches.
- Run hot water with caution to avoid scalding when flushing lines.
Common Homeowner Questions
- Why does removing the aerator make the water stronger? Because the obstruction is in the aerator screen or flow insert; removing it removes the restriction.
- How long should I soak an aerator in vinegar? Typically 30–60 minutes; longer for heavy scale but check periodically to protect plastic parts.
- Could this be a sign of a bigger plumbing problem? If weak flow continues with the aerator off or affects other fixtures, yes — call a plumber for further diagnosis.
For more related articles, see the Low Pressure at Single Fixture hub.