Start by checking whether the problem is everywhere or just at that sink

Low pressure at one sink usually points to a blockage or valve issue specific to that fixture, not a whole-house problem. Turn on every faucet in your home — kitchen, bathroom, outdoor spigot, shower. If pressure is normal everywhere else, the trouble is in the supply lines or aerator feeding that one sink.

If pressure is low throughout your home, the issue is upstream: your main shut-off valve, the meter, or a problem with your water provider. Call your water company to ask whether they are doing work in your area or whether your meter shows normal flow. If pressure dropped suddenly after a plumber was in your home, call them back — they may have left a valve partially closed.

Key Takeaways

  • Low pressure at one sink usually means a clogged aerator or closed shut-off valve under the sink, both of which you can fix in minutes.
  • Unscrew the aerator from the faucet tip, rinse it under running water, and screw it back on — mineral buildup is the most common cause.
  • Check the shut-off valves under the sink by turning the handle parallel to the pipe; if it is perpendicular, turn it until it lines up with the pipe direction.
  • If the aerator and valves are fine, the supply line itself may be kinked or blocked, which usually requires replacing the flexible hose.
  • Pressure that drops suddenly after plumbing work often means a valve was left partially closed — ask your plumber to check before you troubleshoot yourself.

Clean or replace the aerator first

The aerator is the small screen at the tip of your faucet. Mineral deposits from hard water collect there and restrict flow. Unscrew it by hand — turn counterclockwise — or use an adjustable wrench if it is stuck. Hold it under running water from another faucet and rinse it thoroughly. Use an old toothbrush to scrub away white or brown buildup.

If rinsing does not restore pressure, soak the aerator in white vinegar for 30 minutes to dissolve mineral deposits, then scrub again. Screw it back on by hand, turning clockwise until snug — do not overtighten. Turn on the sink and check the pressure. If it is now normal, you are done. If pressure is still low, move to the shut-off valves.

Check the shut-off valves under the sink

Under your sink are two shut-off valves — one on the hot water line, one on the cold. They look like small knobs or handles attached to the pipes coming from the wall. A valve is fully open when the handle points in the same direction as the pipe (parallel). A valve is fully closed when the handle is perpendicular to the pipe.

Turn both handles so they point along the pipe direction. If one was partially closed, opening it may restore pressure when ready. Turn on the sink and test. If pressure is still low at both hot and cold, or if only one temperature has low pressure, the problem is in the supply line itself.

Inspect the supply lines for kinks or damage

The flexible hoses that connect the shut-off valves to the faucet can kink, crack, or develop internal blockages. Look at both the hot and cold lines. If you see a visible kink or crease, that is your problem. Straighten it gently by hand if possible. If the hose is cracked or leaking, it must be replaced.

If the hoses look fine but pressure is still low, the blockage is inside the line where you cannot see it. The fastest fix is to replace both supply lines. Turn off the shut-off valves, unscrew the old hoses from both the valve and the faucet, and screw on new ones. Flexible supply lines cost $5 to $15 per pair at any hardware store and take 10 minutes to swap.

Test the faucet body if the supply lines are clear

If the aerator is clean, the valves are open, and the supply lines are straight and undamaged, the problem may be inside the faucet itself. Mineral buildup can collect in the faucet body and restrict flow. The fix depends on your faucet type — some have a removable cartridge you can soak in vinegar, others require the whole faucet to be replaced.

Look for the faucet model number, usually stamped on the base or the back of the sink. Search online for "[model number] cartridge removal" to see whether your faucet has a replaceable part. If it does and you are comfortable taking it apart, a new cartridge costs $20 to $60 and takes 20 minutes. If you are not sure, a plumber can diagnose and fix it in under an hour.

When to call a plumber instead

If you have cleaned the aerator, opened the shut-off valves, replaced the supply lines, and pressure is still low, the blockage is in the main line between the meter and your house, or in the faucet body itself. A plumber can use a pressure gauge to pinpoint where the restriction is and fix it. This usually costs $100 to $200 for a service call plus repair.

Do not spend more than an hour troubleshooting on your own. The aerator and shut-off valves take five minutes each. Supply line replacement takes 10 minutes. If none of those work, you have a problem that requires tools or knowledge you do not have, and a plumber will get you a working sink faster than trial and error.

Frequently Asked Questions

Why is my hot water pressure low but cold water pressure is normal?

The hot water shut-off valve under the sink may be partially closed, or the hot water supply line may be kinked. Check the hot water valve first — the handle should point along the pipe. If it is already open and the line is straight, the blockage is in your water heater or the line between the heater and the sink, which a plumber will need to check.

Can I fix low water pressure without turning off the water?

Yes, for the aerator and shut-off valve checks. You do not need to turn off water to unscrew the aerator or open a valve. You only need to turn off water if you are replacing the supply lines, to avoid water spraying when you disconnect them.

How do I know if the problem is my water company's fault?

Check pressure at every faucet in your home. If it is low everywhere, call your water company and ask whether they are doing maintenance or whether your meter shows normal flow. If pressure is normal at other faucets, the problem is your sink or the line feeding it, not the company's system.

Will vinegar damage my aerator?

No. Soaking an aerator in white vinegar for 30 minutes to an hour is safe and effective for removing mineral buildup. Vinegar is mild enough that it will not corrode metal or rubber seals. Rinse the aerator thoroughly with water before screwing it back on.

What if I accidentally turn the shut-off valve too hard?

Stop as soon as you feel resistance. Shut-off valves are not meant to be forced. If a valve will not turn, do not push harder — it may be stuck from age or mineral buildup. Call a plumber to open it safely rather than risk breaking it and flooding your home.