Why your water pressure dropped in one faucet — but nowhere else
When pressure drops across your whole house, the cause is usually upstream — a failing pressure regulator, a partially closed main shutoff, or a supply issue from the street. But when the drop is isolated to a single faucet, the problem is almost always inside or immediately upstream of that fixture. The water supply to the rest of your home is completely unaffected, which is actually good news: it narrows the diagnosis considerably. The three most common culprits are a clogged aerator, a compromised faucet cartridge, or a partially closed supply valve under the sink.
The aerator is the small mesh screen screwed onto the tip of the spout. Over time — especially in homes with hard water — mineral deposits (primarily calcium carbonate) build up in that mesh and physically block water flow. The faucet cartridge, which is the internal valve mechanism that controls flow and temperature, can also accumulate scale or simply wear out, restricting flow from inside the body of the faucet. And the shut-off valve beneath the sink — the small oval-handled valve on the supply line — is sometimes bumped partially closed without anyone noticing, particularly after work has been done under that sink.
Less commonly, a section of the supply line feeding just that faucet may have developed a kink, a small internal crack, or a partial blockage due to pipe corrosion. In older homes with galvanized steel pipes, localized rust buildup can restrict a branch line while leaving the rest of the system unaffected. This is rarer but worth knowing, especially if the aerator and valve checks come up clean.
Low pressure in one faucet isn't always the same problem
The same symptom — pressure that suddenly dropped in just one faucet — can have several different root causes depending on the details. Pick the description that fits your situation most closely.
What happens if you leave it alone
A clogged aerator left untreated won't cause structural damage — it will just keep getting worse as mineral buildup continues, eventually reducing flow to a trickle. A partially closed shut-off valve is similarly low-stakes on its own. But if the reduced pressure is a symptom of something more serious — a corroding supply line, a failing cartridge that's beginning to leak internally, or a pinhole developing in a pipe behind the wall — ignoring it can turn a five-dollar fix into a much more expensive repair. The distinction between "annoying but harmless" and "early warning sign" is worth making quickly.
According to the American Society of Home Inspectors, supply-line failures under sinks are among the most common causes of water damage in residential properties — and those failures are frequently preceded by symptoms like reduced pressure or intermittent flow. A supply line replacement costs roughly $10–$30 in parts; the water damage from a burst line can easily run $5,000–$15,000 before remediation. Checking the supply lines while you're already diagnosing the pressure issue takes two minutes and costs nothing.
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What others have experienced
47 community experiences-
DM
Woke up one morning and the kitchen faucet was barely a trickle — every other tap in the house was fine. I was convinced it was something serious. Ended up being the aerator, completely gunked up with white crusty buildup. Soaked it in vinegar overnight, rinsed it, screwed it back on, and the pressure was back to normal. Genuinely could not believe it was that simple after how panicked I was.
34 found this helpful -
RK
Mine was the hot water side only — cold was totally fine. Turned out the cartridge inside the faucet had basically failed on the hot side. I replaced the whole cartridge myself, found the part number on the manufacturer's website, cost me about $18 and maybe an hour including watching a video. A plumber quoted me $180 for the same job. Worth diagnosing it yourself first.
27 found this helpful -
TP
I tried the aerator first, that wasn't it. Then I noticed the shut-off valve under the bathroom sink was only about halfway open — no idea how long it had been like that, probably since we had some work done last fall. Turned it fully counterclockwise, pressure came right back. I felt a little silly but honestly glad it wasn't anything expensive. Check the obvious stuff before you call anyone.
19 found this helpful
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