Low water pressure at faucet
Weak flow at a single faucet is usually a clogged aerator or partially closed supply valve — 15-minute fixes. Whole-house pressure issues point to different problems: pressure regulator, main valve, or municipal supply.
Quick answer
For low pressure at just one faucet: unscrew the aerator at the tip of the spout, soak in vinegar for an hour, brush clean, reinstall. Also verify the supply valves under the sink are fully open (counterclockwise). If pressure is low throughout the house, the pressure regulator or main shutoff is the likely culprit — those require different investigation.
Key facts
| Difficulty | Easy |
|---|---|
| Time | 15–45 min |
| Parts cost | $0–$15 |
| Tools needed | Adjustable pliers, small bowl, old toothbrush, white vinegar |
| Parts needed | Replacement aerator ($3–$8) if damaged |
What's happening
Water pressure to any faucet depends on multiple factors: municipal supply pressure, your pressure regulator (if installed), the main shutoff valve being fully open, each faucet's supply valves being open, and finally the aerator at the faucet tip being clear.
If only one faucet has low pressure, the problem is downstream — supply valves or aerator. If the whole house has low pressure, look upstream — regulator, main valve, or supply line issue.
Aerator clogging is by far the most common issue — mineral deposits (in hard water areas) and sediment build up in the tiny screen at the spout tip. Cleaning takes 15 minutes.
Common causes (ranked by frequency)
- Clogged aerator 50% of single-faucet cases
Mineral deposits or sediment in the aerator screen at the faucet tip. Very common in hard water areas.
- Partially closed supply valve 20% of single-faucet cases
The shutoff valve under the sink got bumped closed or was never fully opened after a repair. Turn counterclockwise to open.
- Clogged supply line filter 15% of single-faucet cases
Some faucets have small filters inside the supply hoses that catch sediment. May need cleaning or replacement.
- Cartridge issue 10% of single-faucet cases
Debris or wear in the faucet cartridge itself, especially in newer single-handle faucets.
- Kinked supply line 5% of single-faucet cases
The flexible supply line under the sink got kinked during a repair or when items were stored beneath.
How to diagnose
Step 1 — determine scope: Does the problem affect just one faucet, all hot water only, all cold water only, or the entire house?
- One faucet only: Aerator or supply valve. Continue below.
- All hot water low: Water heater issue — sediment buildup or dip tube failure.
- Whole house low: Pressure regulator failing, main valve not fully open, or municipal supply issue.
- Sudden and severe: Possible main line break — call water utility.
Step 2 — for single-faucet problems, test the aerator: Unscrew it and run the water. If flow is now strong, aerator is the problem. If still weak, check the supply valves.
Step 3 — check both supply valves under the sink: Hot and cold. Turn counterclockwise as far as they go. If pressure is now good, valves were partially closed.
Step 4 — check supply lines: Look for kinks or crimping. Disconnect and blow through them — should be unobstructed.
The fixes
Clean the aerator TRY FIRST
Tools
- Adjustable pliers
- Small bowl
- Old toothbrush
Parts
- White vinegar (household)
- Optional: replacement aerator ($3–$8) if damaged
- Wrap the aerator in a rag or tape before using pliers — prevents scratching the finish.
- Unscrew the aerator counterclockwise from the faucet tip. Some are recessed and require a special wrench (usually comes with the faucet).
- Disassemble the aerator — screen(s), rubber washer, and housing. Note the order for reassembly.
- Soak all parts in white vinegar for 30–60 minutes. This dissolves mineral deposits.
- Scrub gently with a toothbrush to remove loosened deposits.
- Rinse under running water.
- Reassemble in the same order and hand-tighten back onto the faucet. Snug with pliers if needed — do not over-torque.
Open supply valves fully IF AERATOR IS CLEAN
Tools
- None
Parts
- None
- Look under the sink — you'll see two small valves, one for hot and one for cold.
- Turn each valve counterclockwise as far as it goes. This is fully open.
- If a valve is stuck, don't force it — cheap ball valves ($15) or a plumber can replace.
- Test the faucet after each valve adjustment.
Clean or replace supply line inlet filters IF STILL WEAK
Tools
- Adjustable wrench
- Bucket
- Rags
Parts
- None (unless replacing)
- Turn off supply valves under the sink.
- Disconnect the supply lines from the faucet — a bucket underneath catches drips.
- Look inside the faucet inlets and the supply line ends for small screens or filters — clean or remove obstructions.
- Reconnect and turn valves back on.
Prevention
Preventing low pressure issues:
- Clean aerators annually in hard water areas — quick maintenance.
- Install a whole-house sediment filter if your water contains lots of sediment.
- Consider a water softener if you have very hard water (constant mineral clogging).
- Address municipal pressure issues — install a pressure regulator if house pressure exceeds 80 PSI (which damages fixtures).
When to call a pro
- Whole-house low pressure not resolved by checking main valve
- Suspected pressure regulator failure (over $200 to replace)
- Sudden severe pressure loss (possible pipe break)
- Hot water only affected (water heater diagnosis needed)
- Recurring aerator clogging (indicates water quality issue needing whole-house solution)
Plumber cost: $85–$150 diagnostic visit. Pressure regulator replacement: $250–$500. Whole-house sediment filter install: $200–$500.
Cost estimate
Frequently asked questions
Usually sediment buildup in the water heater (older tanks) or a partially closed hot water shutoff valve. Flushing the tank annually prevents this. If persistent after flushing, dip tube may have deteriorated — pro repair needed.
40–80 PSI is the target range. Below 40 PSI feels weak; above 80 PSI causes fixture damage and pipe wear. A pressure gauge that screws onto a hose bib ($10) confirms your house pressure. Install a pressure regulator if consistently above 80 PSI.
Older homes with 1/2" supply lines can't deliver enough volume to run multiple fixtures simultaneously. Upgrading to 3/4" main and branches solves this — significant plumbing job.
For hard water or sediment issues, yes. Prevents constant aerator clogging, extends fixture life, improves appliance longevity (dishwashers, water heaters). $200–$500 installed.