Low Water Pressure in One Faucet? How to Find and Fix the Cause

When water pressure is low everywhere, the cause is usually outside your control. When it is low at one faucet, the cause is almost always within a few inches of the spout, and you can usually fix it with a bowl of vinegar and an old toothbrush. Start with the question that splits the problem in half.

One faucet or the whole house?

Turn on the cold water in a few other sinks and the shower.

• Only one fixture is weak: the problem is local (aerator, cartridge, shut-off valve or supply line). This guide covers that.
• Every fixture is weak: check that the main shut-off is fully open, ask neighbors whether they have the same issue (could be the utility), and check the pressure regulator if your home has one. A plumber can test static pressure with an inexpensive gauge on a hose bib.
• Only hot water is weak: the issue may be at the water heater (a partly closed valve or sediment), or in the hot side of that faucet.

Fix 1: Clean the aerator (most common)

The aerator is the small screen screwed into the tip of the faucet spout. It mixes air into the stream and catches debris. Over time, mineral scale and grit clog it, especially after plumbing work or a water main repair stirs up sediment.

1. Close the drain so nothing falls in.
2. Unscrew the aerator by hand (counterclockwise looking from below). If it is stuck, wrap it in tape and use pliers gently. Some recessed aerators need a small plastic key that came with the faucet.
3. Take it apart, noting the order of the screens and washer.
4. Soak the parts in white vinegar for 30 minutes to an hour to dissolve scale.
5. Scrub with an old toothbrush, rinse, and reassemble.
6. Before reinstalling, run the faucet for a few seconds without the aerator to flush debris.

If the aerator is damaged, replacements are cheap. Bring the old one to match the thread size (male or female) and diameter.

Fix 2: Clean the showerhead

Same idea: unscrew the showerhead, or tie a bag of vinegar around it overnight if it will not come off, then scrub the nozzles. Some showerheads have a small filter screen where they attach to the arm; clean it with a toothpick.

Fix 3: Check the shut-off valves under the sink

Someone may have partly closed the valve during a repair. Turn each supply valve counterclockwise until it stops. If it is very stiff or leaks at the stem when turned, do not force it; old valves can fail. A quarter-turn replacement valve is a modest upgrade a handy homeowner or plumber can install.

Fix 4: Clean or replace the cartridge

If the aerator is clean and the valves are open but flow is still weak, debris or scale may be inside the faucet cartridge. Shut off the water, remove the handle and cartridge (see our leaky faucet guide for each faucet type), inspect for grit, and rinse. Hold a cup over the opening and briefly turn on the supply valve to flush the line. Replace the cartridge if it is cracked or heavily scaled.

Fix 5: Check the supply line

Flexible braided supply lines can kink, and some have small internal restrictions. With the water off, disconnect the line at the faucet, put the end in a bucket and briefly open the valve. If flow from the line is strong, the problem is in the faucet. If weak, the valve or line is the issue.

Diagnosis checklist

• Compared other fixtures (local vs whole house)
• Compared hot vs cold at the weak fixture
• Cleaned or replaced the aerator
• Confirmed shut-off valves fully open
• Flushed or inspected the cartridge
• Tested supply line flow into a bucket

Hard water: preventing it from coming back

If you clean aerators every few months, you likely have hard water. Signs include white crust on fixtures, spotty glasses and scale in kettles. Options include cleaning on a schedule (put it on your calendar), installing a whole-house water softener, or using fixtures with rubber nozzles that are easier to wipe clean. Many local water utilities publish water quality reports that list hardness.

When the whole house is affected

Common causes: a failing pressure-reducing valve (PRV) near the main, a partially closed main valve, corroded galvanized steel pipes in older homes, or leaks. A plumber can measure pressure and inspect. Typical residential pressure is often cited around 40 to 80 psi; much higher can stress fixtures, much lower feels weak.

Kitchen pull-down faucets

Pull-down and pull-out sprayers have extra places to clog: the spray head itself and a check valve in the hose connection. Unscrew the spray head from the hose (often by hand), check the small screen or check valve at the joint for debris, and soak the head in vinegar if scaled. Make sure the hose is not kinked under the sink and that the counterweight slides freely. Many brands sell replacement spray heads; note the model number usually printed on a tag on the hose or under the sink.

When to replace rather than clean

If the aerator threads are stripped, the cartridge is cracked, or the faucet body is corroded inside, cleaning will not restore good flow. A replacement part or new faucet is the better fix.

Showers with weak flow

Many showerheads include a flow restrictor; US federal standards limit showerheads to 2.5 gallons per minute and WaterSense-labeled models to 2.0 or less. Low flow after cleaning may come from the shower valve's cartridge or an anti-scald balancing spool that is clogged. Shut off water and service it following the valve manufacturer's instructions, or call a plumber if you cannot identify the brand.