Start with the aerator — the fastest fix

The aerator is the small screen at the tip of your faucet. It mixes air into the water stream and often collects mineral deposits that restrict flow. Unscrewing and cleaning it takes five minutes and costs nothing, which is why it should be your first step.

Turn off the water. Unscrew the aerator by hand — it usually twists counterclockwise — or wrap it in a cloth and use pliers if it is stuck. Rinse it under hot water and use an old toothbrush to scrub away white or tan buildup. If the screen is damaged or heavily clogged, replace it with a new one from any hardware store for $3 to $8. Screw it back on and turn the water back on.

If pressure returns to normal, you are done. If it does not, the problem is deeper in the line.

Key Takeaways

  • Clean or replace the aerator first — mineral buildup there is the most common cause of low pressure at a single sink.
  • Check the shutoff valve under the sink; it may be partially closed and restricting flow to just that faucet.
  • If both hot and cold water are weak, the problem is likely in the supply line or the valve; if only one is weak, the issue is in the water heater or its connection.
  • Sediment in the water heater tank reduces pressure over time and can be flushed out, though this requires turning off the heater and draining it.
  • If pressure is low throughout the house, call your water provider to check the main line; if it is low only at your sink, the problem is in your home's plumbing.

Check the shutoff valve under the sink

Below the sink, you will find one or two shutoff valves — one for hot water and one for cold. These are small knobs or levers on the pipes coming up from the wall. If one is partially closed, it will cut pressure to that line without shutting the water off completely.

Turn both valves all the way counterclockwise (or pull levers all the way out, depending on the type). The valve should turn freely and stop when it hits the end of its range. If it is stiff or does not turn all the way, it may be stuck or corroded. Turn it as far as it will go without forcing it.

Turn the faucet on. If pressure improves, the valve was the problem. If not, move to the next step.

Determine whether the problem is hot water, cold water, or both

Turn on only the hot water and note the pressure. Then turn on only the cold water and note that pressure. This tells you where the blockage is.

If only the hot water is weak, the problem is in the water heater or the line between the heater and the sink. If only the cold water is weak, the problem is in the cold water supply line or the main shutoff valve. If both are equally weak, the problem is likely in the aerator (which you already checked) or in a shared line before the hot and cold split.

This information will help you decide whether to call a plumber or try the next steps yourself.

Flush sediment from the water heater

Over time, sediment — minerals and rust particles — settles at the bottom of the water heater tank. This buildup reduces the space available for hot water and can restrict the outlet line, lowering pressure. Flushing the tank removes this sediment.

Turn off the water heater at the breaker or the gas valve. Close the cold water shutoff valve that feeds the heater. Attach a garden hose to the drain valve at the bottom of the tank and run it to a floor drain or outside. Open the drain valve and let the tank empty — this takes 30 minutes to an hour. Close the drain valve, open the cold water shutoff, and turn the heater back on.

This process is straightforward but requires you to be comfortable working with the heater. If you are not, a plumber can do it for $150 to $300. Do not attempt this if you are unsure about your heater's setup.

Check for leaks or damage in the supply line

Look at the pipes under the sink and along the wall where they enter. A pinhole leak, a kink, or a crushed section will reduce pressure. Leaks may be obvious — you will see water dripping — or hidden inside the wall.

If you see a leak or a visibly damaged section of pipe, that section needs to be replaced. This is a job for a plumber unless you have experience with plumbing repair. If you do not see damage but pressure is still low, the problem may be inside the wall or in the main line, and you should call a plumber to diagnose it.

When to call a plumber

Call a plumber if pressure remains low after you have cleaned the aerator, checked the shutoff valve, and confirmed that the problem is isolated to one sink. A plumber can use a pressure gauge to measure the actual flow rate and identify whether the issue is a blockage in the line, a faulty valve, or a problem in the main water supply.

If low pressure affects the entire house, call your water provider first. They can check the main line from the street to your home at no charge. If the main line is fine, then call a plumber to inspect your home's plumbing.

Plumber visits typically cost $100 to $200 for diagnosis and a service call, plus the cost of any repairs needed. The cost of a new shutoff valve or supply line is usually $50 to $150 in parts and labor.

Frequently Asked Questions

Why is pressure low only at my kitchen sink but normal everywhere else?

The aerator is the most likely culprit — mineral deposits collect there first. The second most common cause is a partially closed shutoff valve under that sink. Check both before calling a plumber.

Can low water pressure damage my faucet?

Low pressure itself does not damage a faucet, but the mineral deposits that cause low pressure can eventually corrode internal parts. Cleaning the aerator regularly prevents this buildup.

What is normal water pressure for a sink?

Household water pressure is typically 40 to 80 pounds per square inch (PSI). You can measure yours with a pressure gauge, which costs $10 to $20 at a hardware store and screws onto an outdoor faucet or a hose connection.

Does a water softener increase pressure?

No. A water softener removes minerals that cause buildup, which can prevent future pressure loss, but it does not increase pressure itself. It may actually reduce pressure slightly because the water passes through an additional filter.

Should I replace my aerator with a high-flow one?

High-flow aerators deliver more water per minute but use more water overall. If your goal is to save water, a standard aerator is better. If you want more pressure and do not mind higher water use, a high-flow model costs $5 to $15 and installs the same way as a standard one.