Low sink pressure usually comes from a clogged aerator, a partially closed shut-off valve, or mineral buildup in the lines

When your kitchen or bathroom sink runs slower than it used to, the problem is almost always something you can fix yourself in under an hour. The aerator—the small screen at the tip of your faucet—clogs with sediment and debris. The shut-off valve under the sink gets turned partway closed by accident. Or mineral deposits narrow the water passages inside the faucet body. Each has a different fix, and you'll know which one it is by testing as you go.

Start by checking whether the problem is only at this sink or everywhere in your house. If every faucet is slow, the issue is in your main line or meter, and you should call a plumber. If it's just this one sink, you can almost certainly solve it yourself with basic tools: an adjustable wrench, a flathead screwdriver, and a small brush or old toothbrush.

Key Takeaways

  • The aerator at the faucet tip is the most common culprit and takes two minutes to clean by unscrewing it, rinsing the screen, and screwing it back on.
  • Check the shut-off valve under the sink—it should turn fully counterclockwise and should not be partially closed, which cuts off water flow.
  • If cleaning the aerator and opening the valve don't work, mineral buildup inside the faucet body may require soaking the aerator in vinegar overnight or replacing the faucet cartridge.
  • Test your work after each step by turning the faucet on; you should see pressure return when ready if you've found the right problem.

Clean the aerator first—it's the fastest fix

The aerator is the part you can see and touch. Unscrew it by hand or with a wrench if it's stuck. Most aerators have a threaded collar that twists counterclockwise. Once it's off, you'll see a small screen or mesh inside, usually brass or stainless steel.

Rinse the aerator under running water, then use an old toothbrush or soft brush to scrub the screen. If you see white, chalky buildup (mineral deposits), soak the aerator in white vinegar for 30 minutes to an hour, then brush it again. Rinse thoroughly and screw it back on by hand, turning clockwise until snug. Do not over-tighten—you'll strip the threads.

Turn on the sink and check the pressure. If it's back to normal, you're done. If it's still low, move to the next step.

Check the shut-off valve under the sink

Look under your sink at the pipes. You'll see one or two shut-off valves—small knobs or levers attached to the water lines coming in. These valves let you stop the water supply if you need to repair the faucet or clear a clog.

Turn each valve counterclockwise as far as it will go. It should spin freely and stop when fully open. If a valve is only partway open, that's your problem. Someone may have closed it partially during a repair, or it may have been turned by accident. Open it all the way, then test the sink pressure again.

If the valve is already fully open and the pressure is still low, the problem is inside the faucet itself, and you'll need to go deeper.

Soak the aerator in vinegar for mineral buildup

If cleaning the aerator with a brush didn't work, mineral deposits may be clogging the small holes in the screen or the passages inside the faucet body. Unscrew the aerator again and place it in a cup or small bowl filled with white vinegar. Let it soak for at least two hours, or overnight for heavy buildup.

After soaking, use an old toothbrush to scrub the screen and the inside surfaces. Pay special attention to the small holes—use the brush bristles to poke through them gently. Rinse under running water and screw the aerator back on. Test the pressure.

If pressure is still low, the mineral buildup is likely inside the faucet body itself, behind the aerator. At this point, you have two options: replace the faucet cartridge (the internal part that controls water flow) if your faucet model allows it, or replace the entire faucet.

Replace the faucet cartridge if pressure doesn't improve

Many modern faucets have a replaceable cartridge—a plastic or metal cylinder inside the faucet body that controls water flow and temperature. If mineral buildup is blocking the cartridge, replacing it often restores pressure. However, cartridges are model-specific, so you need to know your faucet brand and model.

Look under the sink or on the faucet body for a brand name or model number. Write it down and search online for the cartridge replacement part. You can order it from a hardware store or online retailer. The cost is usually between $15 and $50.

Replacing a cartridge requires turning off the water at the shut-off valve, removing the faucet handle, and unscrewing the cartridge. Most faucet makers include instructions with the replacement cartridge. If you're not comfortable doing this yourself, a plumber can do it in 30 to 45 minutes.

When to call a plumber instead

If you've cleaned the aerator, opened the shut-off valve, soaked in vinegar, and pressure is still low, the problem is likely inside the faucet body or in the supply line itself. At this point, it's worth calling a plumber rather than spending more time troubleshooting.

Also call a plumber if low pressure affects multiple sinks or if you notice discolored water (brown or yellow) along with low pressure. Discolored water suggests corrosion or sediment in your main line, which requires professional attention.

A plumber can test the pressure at your meter, check for leaks in the supply line, and replace the faucet if needed. A service call usually costs between $100 and $200, plus parts.

Frequently Asked Questions

Why is only the hot water pressure low?

If only hot water is slow, the problem is usually in the hot water line or inside the water heater. Check the shut-off valve on the hot water line under the sink first. If it's fully open, the issue may be sediment buildup in the water heater. Call a plumber to flush the heater or inspect the line.

Can I use a commercial descaler instead of vinegar?

Yes. Commercial descalers like CLR work faster than vinegar on heavy mineral buildup. Follow the product instructions carefully—most require soaking for 15 to 30 minutes. Rinse the aerator very thoroughly afterward, as descaler residue can irritate skin and damage rubber seals.

What if the aerator is stuck and won't unscrew?

Wrap a cloth around the aerator to improve grip, then use an adjustable wrench to turn it counterclockwise. If it still won't budge, soak the base of the aerator in vinegar for 30 minutes to loosen mineral deposits, then try again. Do not force it—you may crack the faucet.

Will replacing the aerator screen with a finer mesh increase pressure?

No. A finer mesh will actually reduce pressure further because it blocks more water. The aerator screen is designed to break up the water stream and prevent splashing; it's not meant to filter. If you remove the screen entirely, pressure will increase but water will splash everywhere.

How often should I clean the aerator to prevent this problem?

In areas with hard water (mineral-rich water), clean the aerator every six months to a year. In areas with soft water, once a year is usually enough. If you notice pressure dropping gradually, that's a sign it's time to clean.