Start with the fastest, low-risk checks

Begin with simple causes that do not require disassembly. These checks can solve many flow problems and also help you narrow down whether the issue is at the faucet, the supply lines, or the home plumbing.

1. Check both shutoff valves under the sink: Look under the sink and make sure the hot and cold supply valves are fully open. A valve that is even partly closed can reduce flow or make one side seem weak. Turn each valve counterclockwise until it stops gently, without forcing it. Then test the faucet again.
2. Test the faucet on both hot and cold sides: Run only the hot water, then only the cold water if your faucet allows it. If one side flows normally and the other is weak, the problem may be in that supply line, shutoff valve, or the faucet cartridge. If both sides are weak, the blockage is more likely at the aerator, spray head, or a shared restriction in the faucet body or house supply.
3. Remove the aerator and test flow: Unscrew the aerator from the faucet tip or spray head if it is removable. Briefly run water into the sink without the aerator. If the flow improves, the aerator is probably clogged with sediment or mineral scale. If the flow is still weak, the restriction is farther upstream.

• Watch for a sudden change after plumbing work, water shutoff, or a nearby leak repair.
• If the flow improves briefly and then drops again, debris may be moving through the line.
• If only one faucet in the home is affected, the issue is likely local rather than a whole-house pressure problem.

Clean the aerator or spray head

Mineral buildup and trapped debris are among the most common causes of poor faucet flow. Cleaning the outlet parts is safe for most homeowners and often restores a normal stream.

1. Disassemble the removable outlet parts: Take off the aerator, spray head, or any screen components according to your faucet’s design. Keep track of the order of washers, screens, and inserts so they go back the same way. If the model is unfamiliar, check the manual before pulling parts apart.
2. Rinse and scrub away debris: Rinse the pieces under running water. Use a soft brush or an old toothbrush to remove grit, sand, or scale. Soaking metal parts in vinegar can help loosen mineral deposits, but avoid soaking finishes or rubber parts unless the manufacturer says it is safe.
3. Reassemble and retest: Put the parts back in the correct order and tighten them snugly by hand. Turn the water on and test the stream. A normal spray pattern or stronger stream after cleaning confirms the clog was at the outlet.

• If the screen tears or the rubber washer is worn, the part may need replacement.
• If your faucet has a pull-down sprayer, check both the main spout and the spray head because either one can restrict flow.
• A badly corroded aerator may need replacing rather than cleaning.

Check for supply-line restrictions under the sink

If the aerator is clean but the faucet still does not flow properly, the next likely causes are kinked, pinched, or partially blocked supply lines. These issues can reduce flow at one faucet without affecting the rest of the house.

1. Look for visible kinks or sharp bends: Inspect the flexible supply hoses under the sink. A hose bent tightly against the cabinet wall or trash container can restrict water. Gently straighten obvious bends and make sure nothing is pressing on the line.
2. Make sure the hose connections are secure and not damaged: Check for signs of bulging, cracking, corrosion, or water leaks at the supply line connections. If you see moisture, shut off the water to the sink and avoid using the faucet until the leak is addressed.
3. Compare hot and cold supply behavior: If one side has strong flow and the other is weak, the issue may be in a single supply hose, shutoff valve, or branch of the faucet. If both sides are equally weak, the restriction is more likely at the aerator, cartridge, or main supply.

• Do not loosen supply fittings while the valves are open.
• A hose that is swollen, brittle, or leaking should be replaced by a qualified person or a homeowner who is comfortable shutting off the water and following the manufacturer’s instructions.
• If cabinet storage is pushing on the hoses, rearrange the space so the lines sit with a smooth curve rather than a tight bend.

Determine whether the cartridge or internal valve is restricting flow

When the aerator and supply lines check out, the faucet’s internal mixing cartridge or valve may be partially blocked by sediment or worn internal parts. This can cause low flow, uneven temperature mixing, or a stream that changes when the handle is moved.

1. Observe how the handle feels: If the handle is unusually stiff, gritty, or has a limited range before the flow increases, the cartridge may have debris inside or may be wearing out. If flow changes when the handle is nudged slightly, that can also point to a cartridge issue.
2. Compare the kitchen faucet with other fixtures: If only this faucet has poor flow and other sinks or showers in the home are normal, the internal faucet parts become more likely than a home pressure problem. If several fixtures are weak, the issue may be broader and should be checked at the home supply level.
3. Stop short of internal repairs if the design is unfamiliar: Cartridge removal and replacement varies widely by faucet model. If your manual does not clearly explain the procedure, or if the faucet is under warranty, consult the manufacturer or a plumber before opening the faucet body.

• Sediment from recent plumbing work can lodge in a cartridge after the water was shut off and restored.
• A worn cartridge may cause inconsistent flow even after the aerator is cleaned.
• Do not force stuck trim pieces or handles; cosmetic parts can crack easily.

Rule out a home-wide water supply problem

Sometimes the faucet is only showing a bigger issue. If multiple fixtures are weak, the problem may involve house pressure, a partially closed main valve, or a pressure-related issue that needs professional attention.

1. Check whether other fixtures are also weak: Run a sink, shower, and an outdoor hose bib if available. If several fixtures have poor flow, the issue is less likely to be the kitchen faucet itself.
2. Look for recent changes to the plumbing system: A recent repair, water shutoff, softener service, or municipal work can temporarily introduce sediment into the system or leave a valve partly closed. If the problem started after work in the plumbing system, mention that timing when you seek help.
3. Contact the appropriate utility or plumber when the issue is widespread: If the whole house has low pressure, or the flow suddenly dropped across multiple fixtures, the problem may be outside the faucet and beyond a simple homeowner fix. A plumber or water utility can check the main supply, pressure regulator, or service line.

• If neighbors have similar issues, the cause may be municipal rather than inside your home.
• A dramatic pressure drop is more urgent if it happens suddenly and affects hot and cold water everywhere.
• Do not bypass or tamper with pressure-regulating devices if you are unsure what they are.

Prevent the problem from coming back

Once the flow is restored, a few maintenance habits can reduce the chance of repeat clogs and make future troubleshooting easier.

1. Clean outlet screens periodically: Rinse the aerator or spray head whenever you notice the stream beginning to narrow, become uneven, or spray off-center. Regular cleaning helps catch sediment before it hardens into scale.
2. Keep under-sink hoses relaxed and visible: Avoid storing heavy items against the supply lines. Leave enough space so the hoses do not kink or twist when cabinet doors open and close.
3. Flush the faucet after plumbing interruptions: If water was shut off for repairs or maintenance, run the faucet for a short period afterward to clear loosened debris before it settles in the aerator or cartridge.

• If your water is very hard, scale buildup may return faster and require more frequent cleaning.
• A small leak or drip can sometimes accompany debris buildup or worn internal parts, so pay attention to changes in sound as well as flow.
• Keep the faucet manual or model information accessible for cartridge or sprayer-specific parts.

Frequently Asked Questions

Why does my kitchen faucet have weak flow only when the spray function is on?

The spray head, hose, or selector mechanism is often the restriction. Clean the spray head screen first, then check for kinks in the pull-out hose. If the regular stream is strong but spray mode is weak, the problem is usually local to the sprayer assembly.

Why does the faucet sputter or spit air?

Air in the line, a partially closed valve, or debris around the aerator can cause sputtering. If the sputtering started after plumbing work or a water shutoff, run the faucet for a short time to purge air and debris. If it continues, inspect the aerator and supply lines.

What if only the hot water flow is weak?

That often points to the hot-side shutoff valve, hot supply line, or the faucet cartridge. Compare hot and cold side performance, then check the hot-side valve for full opening and visible kinks before considering internal faucet parts.

How do I know whether it is the faucet or the house pressure?

If only the kitchen faucet is affected, the problem is usually local to that fixture. If multiple fixtures are weak at the same time, the issue is more likely house-wide, such as a main valve, pressure regulator, or utility supply problem.

When should I call a plumber instead of fixing it myself?

Call a plumber if the supply line is leaking, the faucet still has poor flow after cleaning the aerator and checking the valves, the cartridge appears stuck or model-specific, or the low flow affects several fixtures in the home.

Final Thoughts

Most kitchen faucet flow problems come down to a simple restriction: a clogged aerator, a bent supply line, or a partly closed valve. Start with the easiest checks, then move to the faucet’s internal parts only if the problem stays local and the manual supports the next step.

If the faucet is still not flowing properly after those checks, the next sensible move is to compare other fixtures and decide whether you need a plumber for a cartridge, supply-line, or whole-house pressure issue.