Quick Answer:
The faucet whistles when the flow is low because a restriction is forcing a narrow, high‑velocity jet through a small opening. That jet makes the parts it passes—often the stop valve, the aerator, or the cartridge—vibrate and whistle. Start by checking the shutoff stops and the aerator before replacing larger parts.
Why This Happens
When water is restricted, the same volume must pass through a smaller gap. The faster flow can create turbulence and a focused stream that causes metal or plastic parts to vibrate. Common restriction points are:
- Supply stop (shutoff) partly closed or worn
- Clogged aerator screen or damaged insert
- Worn or damaged cartridge, seat, or washer inside the faucet
If you also notice other symptoms, you may want to check related topics like Low water pressure at one faucet only for additional troubleshooting steps.
Step-by-Step What to Do
1. Try fully opening the stops
Find the small shutoff valves under the sink (one for hot, one for cold). Turn each fully counterclockwise to open. Test the faucet. A partially closed stop is a common cause of low‑flow whistling.
2. Remove the aerator and test the noise change
Unscrew the aerator at the tip of the spout. Run the faucet briefly with the aerator off and listen. If the whistle stops or changes, the aerator or its insert is the likely cause.
3. Slightly reduce flow to see if the whistle changes
Use the faucet handle to lower the flow slightly (don’t throttle the stop). Note whether the pitch or volume of the whistle changes. A change tells you the noise is flow‑dependent and helps confirm a restriction is creating a high‑velocity jet.
4. Clean or replace the aerator or cartridge
- Aerator: Unscrew, take it apart, and clean screens and inserts. Soak parts in white vinegar to dissolve mineral deposits, brush gently, rinse, and reassemble. If damaged, replace the aerator.
- Cartridge: If cleaning the aerator didn’t fix it and the whistle seems to come from inside the faucet, replace the cartridge. Turn off the shutoffs, relieve pressure by running the faucet, remove handle and cartridge, then install a new cartridge that matches your faucet model.
5. If the whistle persists at the stop valve, replace the stop
If the sound seems to originate at the shutoff when you open the valve, the stop may be worn or partly blocked internally. Replacing the valve with a new quarter‑turn stop is a common fix. If you’re not comfortable swapping a valve, call a plumber.
What Not to Do
- Don’t try to “fix” a whistle by partially closing the stop—throttling often makes noise worse.
- Avoid stuffing cloth or tape into the aerator or spout as a permanent fix; that can cause more damage and restrict flow further.
- Don’t use strong chemical descalers inside a cartridge unless the product specifically states it is safe for your faucet—it can damage seals.
When to Call a Professional
Call a plumber if:
- You can’t find the source of the whistle after the aerator and cartridge checks.
- The stop valve is the suspect and you’re not comfortable replacing it.
- The faucet requires soldering, pipe replacement, or the leak risk is high.
If the whistle appeared after a recent DIY change to your fittings, also review guidance on Pressure loss after replacing faucet before proceeding further.
Safety Notes
- Always shut off the local shutoffs before removing cartridges or doing internal faucet work. If no local stops exist, shut off the house water main.
- Relieve pressure by opening the faucet after turning off the stop valves.
- Protect finishes by wrapping jaws or tools with a cloth when loosening fittings.
- If you need to cut or solder pipes, stop and call a licensed plumber—don’t use an open flame if you’re inexperienced.
Common Homeowner Questions
- Why did the faucet start whistling suddenly? A build‑up of mineral deposits, a partly closed stop, or a failing cartridge can suddenly create the restriction that causes whistling.
- Will a new aerator stop the noise? Often yes—if the aerator is the source. Cleaning or replacing the aerator is an inexpensive first fix.
- Is a whistling stop dangerous? No, it’s not dangerous by itself, but it indicates a restriction that can shorten valve life and may signal worn parts that should be replaced.
For more related articles, see the Low Pressure at Single Fixture hub.