Start with the simplest fixes first

Low water pressure in a sink usually comes from one of three places: the aerator (the screen at the tip of the faucet), a closed or partially closed shut-off valve under the sink, or debris in the supply lines. Most of the time, you can fix it yourself in under an hour without calling a plumber.

Before you do anything else, check whether the problem is only in the hot water, only in the cold water, or both. If only one side is weak, the issue is likely in that supply line or its valve. If both sides are equally weak, the aerator is the most common culprit.

Key Takeaways

  • The aerator — the small screen at the faucet tip — clogs with mineral deposits and is the most common cause of low pressure; unscrew it, rinse it, and soak it in vinegar if it is clogged.
  • Check the shut-off valves under the sink by turning the handles all the way counterclockwise; they should turn easily and fully, and partially closed valves cut pressure dramatically.
  • If pressure is low only in hot water, the problem is in the hot water line or its valve; if only cold water is weak, check the cold water valve and supply line.
  • Mineral buildup inside the aerator or supply lines can be dissolved by soaking in white vinegar for several hours or overnight.

Clean or replace the aerator

The aerator is the part you can see — a small cylindrical screen or grid at the very end of the faucet spout. It mixes air into the water stream and also catches sediment and mineral deposits. Over time, calcium and other minerals build up inside it and restrict flow.

Unscrew the aerator by hand or with a wrench if it is stuck. Hold it up to the light and look through it. If you see white, tan, or rust-colored buildup, that is the problem. Rinse it under running water and use an old toothbrush to scrub away loose deposits. If the buildup is heavy, soak the aerator in white vinegar for two to four hours, then scrub again and rinse thoroughly.

Screw the aerator back on and test the pressure. If it is still low after cleaning, the aerator may be damaged inside or the problem is elsewhere. A new aerator costs three to eight dollars at any hardware store and takes thirty seconds to install — just unscrew the old one and screw on the new one by hand.

Check the shut-off valves under the sink

Under your sink, you will find two shut-off valves — one for hot water and one for cold water. They look like small knobs or handles attached to the supply lines coming from the wall. These valves can be partially closed without you realizing it, which cuts water pressure dramatically.

Turn each valve handle counterclockwise (lefty-loosey) as far as it will go. You should feel it turn smoothly and stop after one or two full rotations. If a valve is stiff or only turns partway, it may be stuck or corroded. Try turning it gently; do not force it or you may break it. Once both valves are fully open, test your sink pressure.

If a valve will not turn all the way or feels stuck, it may need to be replaced. This is a job for a plumber, but it is inexpensive — usually fifty to one hundred dollars for the valve and labor. Do not ignore a stuck valve, because you will need it to work if you ever have a leak and need to shut off the water quickly.

Flush the supply lines if pressure is still low

If the aerator is clean and both shut-off valves are fully open, debris or mineral buildup may be inside the supply lines themselves. This is less common but happens in older homes or areas with very hard water.

Turn off both shut-off valves under the sink by turning them clockwise. Place a bucket under the supply lines and loosen the nuts where the lines connect to the faucet (usually two nuts, one for hot and one for cold). Water will drip out. Let it drain into the bucket for a minute or two, then tighten the nuts back up. Turn the shut-off valves back on and test the pressure.

If pressure improves, you have flushed out some debris. If it does not improve, the blockage is deeper in the line or the problem is at the main water shut-off for your home. At that point, a plumber can use a water line flush or replace the supply lines if they are old.

Soak the aerator in vinegar for mineral buildup

Hard water leaves mineral deposits that can clog the aerator even after you have scrubbed it. If cleaning did not fully restore pressure, soak the aerator overnight in white vinegar. The acid dissolves calcium and lime deposits that a brush cannot reach.

Unscrew the aerator and place it in a small cup or jar filled with white vinegar. Let it sit for eight to twelve hours. Remove it, scrub gently with an old toothbrush, and rinse under running water. Screw it back on and test. If pressure is still low, the aerator may have internal damage and needs to be replaced.

Know when to call a plumber

Call a plumber if the pressure is low throughout your entire home, not just at one sink. Low pressure everywhere usually means a problem at the main water shut-off, in the meter, or in the main supply line — things you cannot fix yourself.

Also call a plumber if one of the shut-off valves under the sink will not turn, if you have replaced the aerator and flushed the lines and pressure is still low, or if you see water leaking from the supply lines. A plumber can diagnose the problem in one visit and usually fix it the same day. Expect to pay a service call fee of seventy-five to one hundred fifty dollars, plus the cost of any parts or repairs.

Frequently Asked Questions

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

The problem is in the hot water line or its shut-off valve. Check that the hot water shut-off valve under the sink is fully open. If it is, the hot water supply line may be clogged with mineral buildup. You can try flushing it as described above, or a plumber can replace the line if it is old.

Can low water pressure damage my faucet?

Low pressure itself does not damage the faucet, but the cause of it might. If a shut-off valve is stuck or corroded, it can eventually fail and leak. If mineral buildup is severe, it can damage the internal parts of the faucet over time. Fixing the problem early prevents bigger repairs later.

Is low water pressure a sign of a leak?

Not always. A leak would usually show up as water under the sink or in the cabinet, or as a sudden drop in pressure throughout the home. Low pressure at one sink is almost always the aerator or a shut-off valve. Check for visible water first, then work through the fixes above.

How often should I clean the aerator?

In areas with hard water, clean the aerator every six to twelve months. In areas with soft water, once a year is usually enough. If you notice pressure dropping gradually, that is a sign the aerator needs cleaning sooner.

What if I cannot unscrew the aerator?

Wrap a cloth around it to get a better grip, or use a wrench with a cloth to avoid scratching the finish. If it still will not budge, soak it in vinegar for an hour to loosen mineral deposits, then try again. If it remains stuck, a plumber can remove it without damaging the faucet.