Start by checking whether the problem is hot water, cold water, or both

Low pressure at your bathroom sink usually comes from one of three places: a clogged aerator (the screen at the faucet tip), a shut or partially shut valve under the sink, or a blockage inside the supply line. The first thing to figure out is whether the problem affects hot water only, cold water only, or both—this tells you where to look.

Turn on the hot water tap and note the pressure. Then turn on the cold water tap. If only the hot water is weak, the issue is in your hot water line or heater. If only the cold water is weak, the problem is in the cold water line. If both are equally weak, the aerator or a valve is the likely culprit. Write down which one before you move forward.

Key Takeaways

  • A clogged aerator—the screen at the faucet tip—causes most low-pressure problems and takes five minutes to clean with vinegar and an old toothbrush.
  • Check the shut-off valve under the sink; it should point in line with the pipe, and turning it clockwise closes it, which you never want fully closed.
  • If both hot and cold water are weak, start with the aerator; if only one is weak, the problem is in that supply line and may need a plumber.
  • Mineral buildup in the aerator is normal in hard-water areas and can be prevented by soaking it in vinegar once or twice a year.

Remove and clean the aerator

The aerator is a small cylindrical screen screwed onto the tip of your faucet. It mixes air into the water stream and catches sediment and mineral deposits. Over time, calcium and other minerals build up inside it and restrict flow. This is the most common cause of low pressure and the easiest to fix.

Unscrew the aerator by hand—turn it counterclockwise. If it is stuck, wrap a cloth around it and use a wrench or pliers to loosen it gently. Once it is off, you will see a small screen and possibly a rubber washer inside. Rinse all the parts under running water and use an old toothbrush to scrub away any white or tan buildup. If the buildup is heavy, soak the aerator in white vinegar for 30 minutes, then scrub again.

Screw the aerator back on by hand, turning it clockwise until it is snug. Do not overtighten—you only need it tight enough that it does not leak. Turn the water on and check the pressure. If it is now normal, you are done. If pressure is still low, move to the next step.

Check the shut-off valve under the sink

Under your sink, you will find two shut-off valves—one for hot water and one for cold water. These are small knobs or levers attached to the supply lines coming from the wall or floor. If one of these valves is partially closed, it will restrict water flow to your sink.

Look at each valve. If it has a handle shaped like a lever, it should point in the same direction as the pipe—straight up or straight along the line. If it points sideways or downward, it is partially or fully closed. Turn it gently counterclockwise until the handle points in line with the pipe. Do this slowly and stop as soon as you feel resistance; you are not trying to force it.

If the valve is a round knob, turn it counterclockwise. Again, stop when you feel resistance—do not force it. Turn the water back on and check the pressure. If this fixes it, you are done. If pressure is still low, the problem is inside the supply line itself, and you will likely need a plumber to investigate further.

Identify whether the problem is in the hot or cold line

If cleaning the aerator and checking the valves did not work, you need to know which supply line is blocked. Turn on only the hot water and listen and feel the pressure. Then turn on only the cold water. Note which one is weaker.

If only the hot water is weak, the blockage is in your hot water line between the water heater and the sink, or inside the heater itself. If only the cold water is weak, the blockage is in the cold water line between the main shut-off and the sink. If both are equally weak after you cleaned the aerator, the problem may be at the main shut-off valve for the whole house, which is usually near the water meter or where the line enters the house.

At this point, a licensed plumber should inspect the line. They can use a water pressure gauge to measure the pressure at different points and locate the blockage. Trying to clear a supply line yourself can damage the pipe or fittings.

When to call a plumber

Call a plumber if cleaning the aerator and checking the shut-off valves did not restore pressure. Also call if you notice low pressure throughout the entire house, not just at one sink—this suggests a problem at the main line or water meter that you should not attempt to fix yourself.

A plumber will bring a pressure gauge to measure the water pressure at different points in your system. They can tell whether the blockage is in the supply line, the shut-off valve, or somewhere else. If the line is blocked by mineral buildup or sediment, they may be able to flush it. If the line is damaged, they will recommend replacement.

Prevent mineral buildup in the future

If you live in an area with hard water—water with high mineral content—mineral deposits will build up in your aerator again over time. You can slow this down by soaking the aerator in white vinegar once or twice a year, even if the pressure is still good.

Unscrew the aerator, soak it in a cup of vinegar for 30 minutes to an hour, scrub it with a toothbrush, and screw it back on. This takes less than five minutes and can prevent the problem from returning. Some people also install a whole-house water softener to reduce mineral content throughout the system, but that is a larger project and not necessary for most homes.

Frequently Asked Questions

Can low water pressure at one sink mean a problem with the whole house?

No. If only one sink has low pressure, the problem is in that sink's aerator, valve, or supply line. If all sinks and fixtures in the house have low pressure, the issue is at the main shut-off or water meter, and you should call a plumber.

What if the shut-off valve under the sink will not turn?

Do not force it. A stuck valve can break and cause a leak. Wrap a cloth around it and explore a penetrating oil like WD-40, wait 15 minutes, and try again gently. If it still will not budge, call a plumber to replace it.

Is low water pressure dangerous?

No, low pressure is not a safety hazard. It is only a nuisance. However, if pressure drops suddenly throughout the house, it can signal a leak in the main line, so call a plumber to check.

How long does it take a plumber to fix low water pressure?

If the problem is a clogged aerator or stuck valve, a plumber can fix it in 15 to 30 minutes. If the supply line is blocked and needs to be flushed or replaced, the job may take one to three hours depending on where the blockage is.