Low pressure at one faucet is usually caused by a clogged aerator—unscrew it, clean the screen, and reinstall. If that doesn’t work, check the supply valve under the sink and inspect the supply lines for kinks.
When water pressure drops at just one faucet while the rest of your home has normal flow, the problem is localized. This is actually good news—it means a straightforward fix you can likely handle yourself.
Start with the Aerator
The aerator is the small screen at the tip of your faucet. It’s the most common culprit for single-faucet pressure problems and the easiest to fix.
How to Clean a Faucet Aerator
- Unscrew the aerator by turning counterclockwise (looking up at it)
- Use pliers with a cloth if it’s stuck—protect the finish
- Disassemble the aerator and note the order of parts
- Rinse each piece under water
- Soak in white vinegar for 30 minutes if there’s mineral buildup
- Use a toothbrush to scrub away deposits
- Reassemble and reinstall—test the flow
Before removing the aerator, close the drain or put a towel over it. The small parts can easily fall down the drain and be lost forever.
Signs of a Clogged Aerator
- Water sprays in multiple directions
- Pressure is fine when aerator is removed
- Visible white or green deposits on the screen
- Gradual pressure decrease over time
If pressure improves dramatically with the aerator removed, you’ve found your problem. Consider replacing the aerator if cleaning doesn’t fully restore flow—they’re inexpensive and available at any hardware store.
Check the Supply Valves
Under every sink are one or two shut-off valves (hot and cold). These are your next checkpoint.
Inspecting Supply Valves
- Locate the valves under the sink
- Turn each valve fully counterclockwise to ensure it’s completely open
- Check for leaks around the valve stem
- Test the pressure after opening
Valves sometimes get bumped partially closed during cleaning or storage. A valve that’s only half open will significantly reduce flow.
Valve Problems to Watch For
- Gate valves (round handles) can fail internally—the gate breaks and blocks flow
- Corroded valves may not open fully
- Leaking valves need replacement regardless of pressure issues
If a valve is stuck or won’t turn, don’t force it—you could break the valve or the pipe connection. Apply penetrating oil and let it sit, or call a plumber.
While you’re under there, turn the valves fully closed and then fully open. This annual “exercise” helps prevent them from seizing up when you actually need them.
Inspect the Supply Lines
The flexible lines connecting your valves to the faucet can cause pressure problems too.
Supply Line Issues
Kinks: Flexible supply lines, especially older plastic ones, can develop kinks that restrict flow. Straighten any bends or replace the line.
Clogs: Debris from the water supply or deteriorating internal linings can clog supply lines. Disconnect (with water off) and check for blockages.
Corroded connections: Mineral buildup at the connection points restricts flow. Clean the threads and reinstall, or replace the line.
Replacing a Supply Line
- Turn off the water supply at the valve
- Place a bucket and towels underneath
- Disconnect both ends of the supply line
- Take the old line to the hardware store for sizing
- Install the new line—hand-tighten plus a quarter turn with pliers
- Turn water on slowly and check for leaks
Braided stainless steel supply lines are more durable than plastic and resist kinking. They’re a worthwhile upgrade.
Cartridge or Valve Problems Inside the Faucet
If aerator, supply valves, and supply lines all check out, the problem may be inside the faucet itself.
Symptoms of Internal Faucet Problems
- Pressure varies with handle position
- Hot and cold have different pressure
- Pressure changed after recent faucet work
DIY Cartridge Inspection
- Turn off water supplies
- Remove the faucet handle (screw under cap or set screw)
- Remove the cartridge or valve stem
- Inspect for debris, damage, or mineral buildup
- Clean thoroughly or replace with matching part
- Reassemble and test
Many faucet manufacturers provide lifetime warranties on cartridges. Check before buying a replacement.
When It’s Only Hot OR Cold
If only the hot or cold side has low pressure, the problem is specific to that supply path:
Hot water only: Check the hot water shut-off valve. Also consider water heater issues—sediment buildup can restrict hot water flow.
Cold water only: Check the cold water shut-off valve. If you have a whole-house water filter on the cold line, it may need changing.
Checking for Pipe Corrosion
Older homes with galvanized steel pipes may have internal corrosion that restricts flow.
Signs of Pipe Corrosion
- Pressure is worse at faucets farthest from the water main
- Brown or rusty water, especially when first turned on
- Pinhole leaks developing in pipes
- Gradual pressure loss over months or years
If you suspect pipe corrosion, have a plumber evaluate whether partial or full repiping is needed. This is beyond DIY territory but important for long-term water quality and pressure.
Prevention Tips
- Clean aerators annually before buildup becomes severe
- Exercise shut-off valves yearly to keep them functional
- Install a whole-house water filter if you have sediment issues
- Upgrade old supply lines to braided stainless steel
- Address hard water with a water softener to reduce mineral buildup
When to Call a Plumber
Contact a professional if:
- DIY fixes don’t restore pressure
- You find corroded or damaged pipes
- Supply valves won’t turn or are leaking
- Multiple faucets start having pressure problems
- You’re uncomfortable working on plumbing
For more comprehensive plumbing guidance, see our complete Plumbing Fixes Guide.
Next Steps
If you’ve ruled out single-faucet causes, you may have a whole-house pressure problem that requires different troubleshooting. Also ensure you know the location and operation of your home’s shut-off valves before working on any plumbing.