Low water pressure in a kitchen sink is usually the faucet itself: a scaled or grit-clogged aerator, a blocked screen in a pull-down spray head, a worn cartridge, or a supply stop under the sink that is not fully open. Test before you touch anything. If the bathroom taps and the tub run normally, the problem lives between the under-sink stops and the spout, and you can check most of it yourself. If every fixture is weak, it is a whole-house problem and a licensed plumber's call.
That split, one fixture or the whole house, decides everything that follows, so it comes before any tool.
Step one: the three-tap test
Run cold water at the kitchen sink, then at a bathroom sink, then at the tub. Repeat with hot water. The results sort the problem into one of a handful of boxes.
| What you see | Where it points | Who handles it |
|---|---|---|
| Kitchen weak on hot and cold, everything else normal | Aerator, spray head screen or cartridge | You, with the steps below |
| Kitchen weak on one side only | That side's supply stop, supply line or cartridge | You, up to the stop; a plumber past it |
| Hot weak everywhere, cold fine everywhere | The water heater or the pipe leaving it | The heater's manual, then a licensed plumber |
| Every fixture weak, hot and cold | Main shutoff, pressure regulator, supply pipe or the utility | Your water utility or a licensed plumber |
| Sudden drop everywhere, plus damp patches or a moving meter | A leak | Close the main shutoff and call a licensed plumber |
| Weak only since recent plumbing work or street water main work | Grit knocked loose into the aerator or cartridge | You, usually starting at the aerator |
The last row is the one people miss. Work on a water main, or a plumber shutting your water off and on again, can shake sediment loose inside the pipes. It travels until it meets the first fine screen, which is the aerator at the end of your faucet.
Low water pressure in kitchen sink: start with the aerator
The aerator is the small screened cap threaded onto the tip of the spout. It mixes air into the stream and, on most modern faucets, limits the flow. It is also the finest filter between your pipes and your glass, so scale and grit stop there first.
- Close the drain or lay a towel in the sink so small parts cannot fall in.
- Unscrew the aerator by hand. If it is stuck, wrap it in a cloth before using pliers so the finish is not marked.
- Note the order of the parts as they come out. There is usually a screen, a flow insert and a rubber washer.
- Turn the water on briefly with the aerator off. If the flow is suddenly strong, you have found the problem.
- Rinse grit off the screen. For white, crusty mineral scale, soak the metal parts in plain white vinegar until the deposit softens, brush them with an old toothbrush, and rinse well.
- Reassemble in the same order and thread it back on hand-tight.
Use the vinegar on its own, never mixed with bleach or any other cleaner. Combining cleaning products can release toxic gas. The EPA's brief guide to mold, moisture and your home, updated February 2026 and read on 2026-09-11, states the most common version plainly: never mix chlorine bleach solution with cleaning products that contain ammonia, because toxic fumes could be produced.
If the parts are cracked, or the scale will not shift, a replacement aerator is a small part. Take the old one to the store so the thread size and flow rating match.
If scale is what you found, it will come back. That white crust is the same mineral load that leaves film on glassware and furs up a kettle. The signs of hard water in the house explains how to confirm it from your utility's water quality report rather than guessing.
Pull-down and pull-out spray heads
Many pull-down and pull-out kitchen faucets have a second screen, and sometimes a small check valve, where the hose meets the spray head or where the hose connects under the sink. The spray head usually unscrews from the hose. If the aerator is clean and the flow is still weak, this is the next place to look, following the maker's instructions for your model. The brand is usually on the base or the handle, and the model number is often on the original paperwork or a tag under the sink.
A kinked hose produces the same symptom. When a pull-down hose snags on its counterweight or on things stored in the cabinet, the flow drops. Clear the space around it and pull the spray head in and out to check that the hose moves freely.
Measure the flow instead of guessing
"Low pressure" is a feeling. Flow rate is a number you can check.
EPA's WaterSense page on bathroom faucets, updated June 2026 and read on 2026-09-11, cites a federal standard flow of 2.2 gallons per minute and a WaterSense maximum of 1.5 gallons per minute. Many aerators have their rated flow printed on the side, and that printed number is your benchmark.
The test: put a one-gallon container under the faucet, open it fully, and time how long it takes to fill.
- At 2.2 gallons per minute, a gallon takes a little over 27 seconds.
- At 1.5 gallons per minute, it takes 40 seconds.
If your aerator is rated at 1.5 and the gallon fills in about 40 seconds, the faucet is doing exactly what it was built to do. The "problem" is that a low-flow aerator was fitted, perhaps with a new faucet. If the gallon takes far longer than the rated flow allows, something is restricting it. Most troubleshooting guides skip this, and it saves people from chasing a fault that does not exist.
The supply stops under the sink
Open the cabinet. You should see two small valves, one for hot and one for cold, with flexible supply lines running up to the faucet.
- Check they are fully open. A stop someone half-closed during an earlier repair will cut the flow on that side. Turn each one counterclockwise gently until it stops. Do not force it.
- Look at the supply lines. A kinked or crushed line restricts flow. A braided line with a bulge, or corrosion at the fittings, is due for replacement.
Stop here if anything resists. Older multi-turn stops can seize, and forcing one can snap the stem or start a leak at the packing nut, which leaves you with a valve you cannot close. If a stop will not turn, drips from the stem when moved, or its fittings are corroded, book a licensed plumber rather than pushing on. Before any under-sink work, know where your home's main water shutoff is, so that if something does start leaking you are not searching for the valve with water on the floor.
The cartridge
If the aerator is clean, the spray head is clear, the stops are open and the flow is still weak on both sides, the cartridge inside the faucet body is the next suspect. It is the part the handle moves, and grit or scale can partly block its ports.
Replacing a cartridge is fixture-side work done with both supply stops closed. The faucet maker's instructions for your model are the only ones worth following, because cartridges differ by brand and even by model year. If the stops will not close, if parts are no longer made for the faucet, or if the faucet body itself is corroded, the realistic options are a licensed plumber or a replacement faucet.
When only the hot water is weak
Weak hot water at the kitchen sink alone points back to the hot supply stop or the hot side of the cartridge. Weak hot water at every tap points away from the faucet, toward the water heater or the pipe leaving it. Sediment in a tank heater is one common cause.
We stop at the diagnosis here. A water heater has a gas or electrical supply, a temperature and pressure relief valve, and water hot enough to scald. Your heater's own manual says what the owner may maintain. Anything touching the gas supply, the electrical supply or the relief valve is a licensed plumber's work, and on a gas unit, the gas utility's or a licensed gas fitter's.
When it is the whole house
If every fixture is weak, the kitchen faucet is just where you noticed it. Common causes include a main shutoff not fully reopened after work, a failing pressure-reducing valve on the incoming line, corroded older supply pipe, a leak, or a problem on the utility's side.
A few things you can do before anyone arrives:
- Ask the neighbors. If they have the same problem, call your water utility first.
- Check the main shutoff is fully open, if you know where it is and it turns freely.
- Watch the water meter with every tap and water-using appliance off. If the dial moves, water is going somewhere, and that is a leak until proven otherwise. The EPA's Fix a Leak Week page, updated March 2026 and read on 2026-09-11, states that nine percent of homes have leaks that waste 50 gallons or more per day.
Past that point you are into pressure regulators, main-line pipework and, depending on where you live, permits. That is a licensed plumber's job, not a weekend one.
Scale in the aerator usually means scale elsewhere
Scale rarely stops at one fixture. If you have been descaling a coffee maker that brews more slowly each month, or a kettle that furs up within weeks, the same water is doing both jobs. Descaling a coffee maker that brews slowly and how often to descale a kettle cover the other two ends of the same problem. In a hard-water house, it makes sense for the kitchen aerator to join that routine.
FAQ
Why is the water pressure low in my kitchen sink but fine everywhere else? Because the restriction is in the kitchen faucet or its supply: usually the aerator, the spray head screen, a supply stop not fully open, or the cartridge. A problem that affects one fixture only is rarely a whole-house issue.
Can a clogged aerator really cause low water pressure? Yes. It is the finest screen between your pipes and the spout, so grit and mineral scale collect there first. Unscrewing it and running the tap without it is the most direct test there is.
Why did my kitchen faucet pressure drop after the water was shut off? Shutting the supply off and restoring it, whether by a plumber or during utility work on the main, can dislodge sediment in the pipes. It usually ends up in the aerator or the cartridge. Clean the aerator first.
When should I call a plumber for low water pressure? When every fixture is weak, when the water meter moves with everything off, when a supply stop will not turn or leaks, or when hot water is weak throughout the house. Those are past the faucet and into the system.
The short version
Test three taps before you pick up a tool. If only the kitchen is weak, work from the tip of the spout backward: aerator, spray head, supply stops, cartridge. If the whole house is weak, the faucet is only the messenger, and the right next call is your water utility or a licensed plumber.
