A clogged faucet aerator that turns a strong stream into a sad trickle
If your kitchen sink used to blast through stuck-on taco-night dishes and now barely rinses a spoon, start at the very tip of the faucet. Most faucets have an aerator, which is a small screen that mixes air into the water to reduce splashing. In real-life kitchens, it also catches grit, tiny bits of scale, and debris from the plumbing.
What to do: Unscrew the aerator (usually by hand, sometimes with a cloth-wrapped pliers grip). Rinse the screen, and soak it in white vinegar for 20 to 30 minutes if you see crusty buildup. Flush the faucet briefly with the aerator off (aim into a bowl) to clear loose debris, then reinstall. If the faucet suddenly runs strong again, you found the problem.
When it’s not “pressure” at all: Some faucets are designed to limit flow to save water. For example, EPA WaterSense-labeled bathroom faucets max out at 1.5 gallons per minute compared with the older 2.2 gpm standard, so they can feel weaker even when pressure is fine (EPA WaterSense guidance). If your “low pressure” only happens at one faucet and the rest of the house feels normal, the aerator or faucet design is the usual culprit.
A blocked spray head or pull-down hose in the kitchen faucet
Kitchen faucets with pull-down sprayers are convenient, but they have more places for restriction. The spray head often has tiny rubber nozzles that trap mineral scale, and the hose can kink under the sink when cleaning supplies get shoved around.
What to do: Wipe the nozzles with your thumb to break loose buildup, then run hot water for a minute. If your faucet has a spray head you can remove, soak it in vinegar and rinse. Under the sink, make sure the hose makes a smooth loop and isn’t pinched by a trash can, a stack of sponges, or the edge of the cabinet.
Tip: If pressure is weak only when the sprayer is attached but strong when you disconnect it at the quick-connect fitting, the spray head is restricting flow.
A dirty cartridge inside the faucet
Inside many modern faucets is a cartridge, a replaceable valve assembly that controls mixing and volume. As it wears, it can trap grit and hard-water scale, causing low pressure, uneven flow, or sputtering.
What to do: Turn off the hot and cold shutoffs under the sink, remove the handle, and pull the cartridge. Rinse it and check for debris. If it’s rough, swollen, or cracked, replace it with the correct part for your faucet model. This is one of the most common “hidden” fixes because it restores flow without replacing the whole faucet.
What not to do: Don’t force the handle harder when flow drops. That can damage internal parts and turn a simple cartridge swap into a bigger repair.
A shutoff valve that’s only partly open
Under-sink shutoff valves get bumped, turned halfway during a repair, or slowly stiffen with age. The valve may be open “enough” to run water, but not enough to deliver a strong stream. These valves are usually angle stops, which means a small shutoff located at the wall below the sink.
Here’s a quick, homeowner-friendly checklist to pinpoint whether the valve is the bottleneck:
- Turn the cold water on at the faucet and note the strength.
- Look under the sink and turn the cold shutoff fully open (counterclockwise), then retest.
- Do the same for the hot shutoff.
- If the valve feels stuck, don’t crank it with brute force; gently work it back and forth.
- If flow improves only when you jiggle or partially close the valve, the valve may be failing internally and should be replaced.
If opening the valve helps right away, you’ve solved it. If the valve won’t fully open or starts dripping around the stem, it’s time for a replacement before it turns into a leak in the cabinet.
Hard water scale that slowly chokes off flow
In San Antonio, TX, hard water is a real-life factor, not a marketing scare. San Antonio Water System notes typical hardness ranges around 15 to 20 grains per gallon, which is considered very hard and is plenty to leave mineral scale inside fixtures over time (SAWS water quality FAQ). That crusty buildup (mostly calcium and magnesium minerals) can narrow passages inside faucet bodies, showerheads, and valves.
What to do: If aerators and sprayers keep clogging every few months, treat that pattern as a clue. Regular vinegar soaks help, but they don’t stop buildup inside the plumbing. A whole-home softener reduces scaling by removing hardness minerals before they settle in your fixtures, and it can also help protect appliances like dishwashers and water heaters.
Pressure vs. flow (the myth that trips people up): Pressure is the “push” in the pipes; flow is how much water actually comes out. Hard water scale often reduces flow at the fixture even when pressure in the home is normal. That’s why the sink feels weak, but your pressure gauge (if you have one) might still read fine.
A clogged supply line or failing shutoff valve under the sink
Even if the valve is fully open, the short braided line feeding your faucet can clog internally with sediment. Some older shutoff valves also shed rubber or corrosion that ends up stuck at the inlet of the supply line.
What to do: Shut off the valve, remove the supply line from the faucet, and aim it into a bucket. Crack the valve open briefly to see how strong the flow is coming directly from the shutoff. If it’s weak there, the valve or pipe feeding it is the issue. If it’s strong there but weak when connected to the faucet, the restriction is in the faucet or supply line.
Quick win: Swapping the supply line is inexpensive and often restores flow. If the shutoff valve itself is the weak link, replacing it prevents future clogs and reduces the chance of a surprise leak.
A pressure-reducing valve that’s out of adjustment or wearing out
Many homes have a pressure-reducing valve, or PRV, which is a bell-shaped regulator on the main water line that lowers incoming city pressure to a steady level for the house. When it fails or drifts out of adjustment, the whole home can feel weak at once: showers, sinks, laundry, everything.
What to look for: Low pressure throughout the house, pressure that changes randomly, or pressure that seems fine early in the day but drops during heavy use. A PRV can also clog with debris and behave like a partially closed valve.
What to do: This is a good time to use a simple pressure gauge on an outdoor spigot. If the reading is unusually low, or if it swings wildly when a faucet turns on, the PRV may be failing. Replacement is often more reliable than trying to nurse an old one back to life.
A hidden leak or pipe problem stealing your pressure
A leak doesn’t always announce itself with a puddle. A pinhole in a pipe, a slab leak, or a failing fitting can divert water away from fixtures and reduce pressure. You might notice a faint hissing sound, damp spots, warm areas on the floor, or a water bill that creeps up.
What to do: If pressure dropped suddenly and you can’t tie it to one fixture, check for obvious signs: wet cabinet bottoms, moisture around the water heater connections, and any area that smells musty. Also pay attention to whether the water meter moves when no water is running, which can be a big clue.
What not to do: Don’t ignore “minor” drops that come with a bigger bill. Leaks rarely stay minor, and the damage can be far more expensive than the repair.
Mineral buildup, aging pipes, or city-side issues you can’t fix with a wrench
In older homes, especially those with galvanized steel piping, the inside of the pipe can narrow over decades due to corrosion and scale. It’s like cholesterol in an artery: water can still move, but not like it used to. You’ll often see low pressure at multiple fixtures, and cleaning aerators becomes a constant chore.
There are also times when the issue isn’t inside your house at all. Neighborhood work, valve adjustments, or a partially blocked main line can cause widespread drops. In parts of San Antonio, TX, you might also feel pressure changes during high-demand times, like early mornings.
What to do at home: Confirm whether the problem is isolated or whole-house. If every fixture is weak, it’s time to stop chasing aerators and look upstream at the regulator, main shutoff, or service line.
A gentle, money-saving move: This is where calling the right pro can actually prevent wasted DIY spending. If you’ve cleaned fixtures and checked valves but pressure stays low, PlumbSmart can track down the cause fast, whether it’s a faucet issue or something bigger. A proper diagnostic visit often beats replacing parts at random. If the problem is limited to your sink, start with kitchen plumbing repair. If you suspect water is escaping somewhere you can’t see, leak detection and repair can pinpoint it before damage spreads. And if the pressure drop traces back to the supply coming into the home, main water line repair is the right next step.
One more safety note when replacing parts: anything that contacts drinking water should be certified for health effects. Look for components that meet NSF/ANSI 61, a standard that sets health-effects requirements for materials used in drinking-water system components (NSF overview of NSF/ANSI 61). It’s an easy way to avoid “mystery metal” problems when you swap a valve, faucet, or fitting.
