Start with the shut-off valve under the sink

The fastest fix for low kitchen sink pressure is the shut-off valve underneath the basin. This valve controls water flow to that sink alone, and it often gets partially closed by accident — during repairs, cleaning, or straightforward from age. A valve that is even slightly turned can cut your pressure in half.

Look under your sink at the pipes coming from the wall. You will see one or two oval knobs or levers (one for hot water, one for cold, or sometimes a single combined valve). Turn each one counterclockwise as far as it will go without forcing it. Do not use a wrench; hand-tight is correct. Run the sink for 30 seconds and check the pressure. If it jumps, you have found the problem.

If the valve is already fully open and pressure is still low, move to the next step. If turning it made no difference, turn it back to where it was — you may have a different issue downstream.

Key Takeaways

  • The shut-off valve under your sink is the first place to check; even a quarter turn can reduce pressure, and opening it fully often solves the problem.
  • Aerators (the screen at the sink's mouth) clog with mineral deposits and are cheap to clean or replace, usually costing under $10.
  • If only the kitchen sink is weak but other faucets are normal, the problem is local to that sink, not your whole house.
  • Mineral buildup inside supply lines requires soaking the aerator in vinegar or replacing the line itself, which takes 20 minutes and basic tools.
  • If pressure is low everywhere in your house, the issue is in your main line or meter, and you will need to contact your water company or a plumber.

Clean or replace the aerator

The aerator is the small screen or grid at the tip of your faucet. It mixes air into the water stream and catches debris. Over time, mineral deposits and sediment build up inside it and block flow. This is the second most common cause of low kitchen sink pressure, and it costs almost nothing to fix.

Unscrew the aerator by hand (turn it counterclockwise). If it is stuck, wrap a cloth around it and use pliers — grip the cloth, not the aerator itself, to avoid scratching the finish. Once it is off, hold it up to the light. If you see white, tan, or rust-colored buildup inside, that is your culprit.

Soak the aerator in white vinegar for 30 minutes to an hour. Use an old toothbrush to scrub away the deposits, then rinse it under running water. Screw it back on and test the pressure. If soaking does not work, or if the aerator is cracked or corroded, buy a replacement at any hardware store for $3 to $8. They are universal and take 10 seconds to install.

Check for a clogged supply line

If cleaning the aerator did not help, the problem may be inside the flexible supply line that runs from the shut-off valve to the faucet. These lines can collect sediment or mineral buildup over years, especially in areas with hard water. Unlike the aerator, you cannot soak a supply line, but you can replace it.

Turn off the shut-off valve under the sink (turn it clockwise). Place a bucket underneath and unscrew the supply line from the shut-off valve using an adjustable wrench — turn counterclockwise. Then unscrew it from the faucet inlet (usually at the base of the faucet, under the sink). The line will drip; that is normal.

Take the old line to a hardware store and buy an identical replacement. They cost $5 to $15 depending on length. Screw the new line onto the shut-off valve first, then onto the faucet. Turn the shut-off valve back on and run the sink for a minute to flush out any debris. If pressure improves, the old line was clogged. If not, you have a different problem.

Determine whether the problem is only at your kitchen sink

Before you call a plumber, test the pressure at other faucets in your house. Run the bathroom sink, shower, and any outdoor hose. If those all have strong pressure and only the kitchen sink is weak, the issue is local to that sink — aerator, supply line, or shut-off valve — and you can fix it yourself with the steps above.

If pressure is low everywhere in your house, the problem is in your main water line, meter, or the supply from your water company. This is not something you can fix at the sink level. Contact your water company first; they can test the pressure at your meter for free and tell you whether the issue is on their side of the line or yours. If it is on your side, you will need a plumber to inspect the main shut-off valve or the line itself.

What to do if the shut-off valve is stuck or broken

If the shut-off valve under your sink will not turn, or if it leaks when you try to open it, it may be stuck from mineral buildup or straightforward worn out. Do not force it; forcing a stuck valve can break it and cause a flood.

Try wrapping the valve handle in a hot, damp cloth for a few minutes to soften any mineral deposits, then try turning it gently. If it still will not move, leave it alone and move on to the other steps. If it leaks when you turn it, it is failing and should be replaced. This is a 15-minute job for a plumber and costs $75 to $150 in most areas. Until then, you can still clean the aerator or supply line to improve pressure.

When to call a plumber

Call a plumber if pressure is low at multiple faucets throughout your house, if the shut-off valve is stuck or leaking, or if you have replaced the aerator and supply line and pressure is still weak. A plumber can test the pressure at your meter, inspect your main shut-off valve, and check for leaks in your line that you cannot see.

You should also call if you are not comfortable working under the sink or unscrewing supply lines. The job is straightforward, but if you strip a fitting or cross-thread a connection, you can create a leak. A plumber will get it right the first time and usually charges $100 to $200 for a service call plus any parts.

Frequently Asked Questions

Why is only my kitchen sink pressure low?

The problem is almost always the aerator, supply line, or shut-off valve at that sink. These parts clog or wear out independently of the rest of your house. Test other faucets to confirm they are normal, then follow the steps above to clean or replace the aerator and supply line.

Can I use a wrench on the shut-off valve?

You can use a wrench if the valve is stuck, but grip the valve body itself, not the handle, to avoid breaking the handle. For normal operation, hand-tight is all you need. If the valve is so stuck that you cannot turn it by hand, do not force it — call a plumber to avoid damage.

What if vinegar does not clean the aerator?

If soaking in vinegar for an hour does not remove the buildup, the aerator is too clogged to save. Buy a replacement for $3 to $8 at any hardware store. They are universal and screw on in seconds. Replacement is faster and cheaper than fighting a stubborn aerator.

How do I know if my water company has a pressure problem?

Call your water company and ask them to test the pressure at your meter. They do this for free. If the pressure at the meter is below 40 pounds per square inch (PSI), the problem is on their side. If it is normal at the meter but low at your sink, the problem is in your house line.

Is low water pressure a sign of a leak?

Not always. A leak usually shows up as wet spots under the sink, in your walls, or in your yard. Low pressure at one sink is almost always a clogged aerator or supply line. Low pressure everywhere in the house could be a leak, but it could also be a problem at your meter or with your water company. Test other faucets first.