A clogged aerator is the most common reason a single faucet loses pressure while the rest of the house runs fine. A dirty aerator isn’t always the culprit, though, and knowing the difference matters before assuming you’ve found the fix.
What an Aerator Does and Why It Clogs
The aerator is the small mesh screen screwed onto the end of your faucet spout. It mixes air into the water stream for a smooth, even flow without splashing. Over time, mineral deposits (mostly calcium and magnesium from hard water), sediment, and debris collect in the mesh and restrict flow.
Water hardness varies across the Bay Area. San Francisco water is quite soft, while parts of the South Bay and East Bay run harder. If you live somewhere with harder water and haven’t had the aerator cleaned in a year or two, it’s a reasonable first thing to check.
What Aerator Cleaning Involves
Cleaning an aerator means unscrewing it from the spout tip, separating the internal parts (housing, rubber washer, one or two mesh screens), soaking them in white vinegar to dissolve mineral deposits, scrubbing with a small brush, and reassembling in the correct order.
On Kohler faucets, the aerator is a cache-style unit recessed inside the spout. Removing it requires a specific plastic cache key, not pliers. Using pliers on a cache aerator will damage the seat. Getting the parts back in the right order matters, too.
If the aerator is corroded in place, or you’re not sure what you’re dealing with, a licensed plumber can handle it as a straightforward service call.
When Cleaning Doesn’t Fix It
If the aerator is clean and pressure at that faucet is still weak, the problem is upstream. Most common causes, roughly in order:
Partially closed shutoff valve. The angle stop under the sink (or behind the wall for a shower valve) may not be fully open. These get bumped during cleaning or other work. Check that it turns counterclockwise as far as it goes, then retest.
Kinked supply line. The braided lines from the shutoff to the faucet can develop a kink if something got pushed against them under the sink. Pull out what’s stored there and look. A kinked line needs replacement.
Cartridge restriction. Sediment can lodge in the valve cartridge, especially after the water was shut off and turned back on. Clearing or replacing a cartridge means disassembling the faucet handle and internals. That’s plumber work.
PRV set too low or failing. If multiple fixtures have low pressure (not just one), the pressure-reducing valve on the main line is the more likely cause. PRVs wear out and sometimes drift low over time, typically well below the normal 50 to 60 PSI range. Adjustment or replacement is a job for a licensed plumber.
Corroded pipe upstream. Galvanized steel pipes, common in older Bay Area homes, corrode internally over decades. If the restriction is in the branch line feeding that faucet, no aerator cleaning will fix it.
A Note on Kohler Faucets
Kohler’s cache aerator sits recessed inside the spout tip, so you won’t see anything to grab with pliers. The plastic cache key is inexpensive and available at any hardware store. Kohler’s website has model-specific installation guides if you want to confirm your faucet’s aerator configuration before a plumber comes.
When to Call a Licensed Plumber
If cleaning the aerator doesn’t restore flow, or if you run into any of the situations below, get a licensed plumber to diagnose it:
- Low pressure at more than one fixture
- A shutoff valve that won’t fully open or feels stiff
- Supply lines that look corroded, bulging, or damaged
- Any work on the PRV or main supply line
In California, plumbing work beyond minor fixture maintenance requires a C-36 licensed plumber. Verify any plumber you hire at cslb.ca.gov before work starts. It takes thirty seconds and protects you.
An aerator is worth checking first. It just isn’t the fix for every pressure problem, and a licensed plumber can diagnose the real cause faster than chasing it yourself.