Why does my faucet squeal or screech?

Inside the faucet body sits a cartridge on a single-handle faucet, or a stem with a washer on an older two-handle faucet. Both control flow with rubber seals. When a seal dries out, hardens or picks up scale, water squeezing past it can make it chatter, and the chatter is the squeal you hear.

Moen's troubleshooting page for a faucet handle that is hard to operate points to the same parts. Its typical cause "is usually caused by (but not limited to) sediment or debris in the cartridge, mineral buildup or a damaged seal within the cartridge." The page addresses a stiff handle, not a squeak, so read it as a list of what wears out in there, not a diagnosis of your noise. Phoenix water is hard, so scale in a cartridge is not unusual here.

The fix is to service or replace the cartridge. Which one you own matters, because they are not interchangeable. If you have a Moen, see how to identify a Moen faucet cartridge. For a Delta, see how to replace a Delta faucet cartridge. If a faucet is also dripping, how to fix a dripping faucet covers the parts involved.

One warning before you reach for a lubricant. Moen says one-handle faucets with a 1225 cartridge can be serviced by lubricating it "both inside and out with a silicone-based grease." It then says: "Do not use plumber's grade faucet grease, silicon sprays or any lubricant that may contain petroleum." Its reason is that "petroleum-based lubricants may react with the rubber seals and could cause the handle to become even more difficult to operate." Check your own manufacturer's instructions before you grease anything.

Under a sink you will find a small shutoff valve, called an angle stop, on each supply line. If a valve is only partly open, water has to squeeze through a narrow gap, and a narrow gap can whistle. Lennox, writing about water heaters, describes the same physics: "When water is forced through a tight space, like a partially closed valve or mineral-clogged pipe, it creates turbulence and that characteristic screech." A shutoff valve under a faucet is a different fixture, but the principle is the same. Turn the handle on each angle stop slowly counterclockwise until it is fully open and listen again. If a valve has been closed for years, open it gently so it does not start dripping at the stem.

Next, the aerator: the small screen at the tip of the spout. Scale and grit collect there, and a partly blocked screen can hiss or whine. Unscrew it, rinse it, and soak it in white vinegar if it is crusty. Our page on why water flow is low at just one faucet has the full steps. If the noise stops when the aerator is off, you found it. Run the water for a moment with it off to flush any debris out of the spout before you reinstall it.

If the shutoff valve and the aerator check out, the valve itself may be failing. If a shutoff valve still squeals when it is fully open, its internal parts may be worn, and the valve can be replaced. See how to shut off water to a single fixture so you can work on one faucet without turning off the whole house.

When more than one fixture screeches, look at the whole house. Zurn Wilkins says in its installation sheet that "high velocity tends to cause whistling and humming." Its troubleshooting table gives a high velocity of flow as the usual cause of a hum or whistle, and says "frequently noise appears in a faucet or appliance and seems to originate from the reducing valve." In other words, the noise you hear at a faucet may start at a regulator or an undersized pipe.

The Zurn sheet also says "chatter usually originates with worn seat washer or loosely installed seal ring." That line is about pressure regulators, but it is a useful reminder that a worn seat washer is a classic noise source in any valve, whether it is a faucet or a regulator.

Pressure matters here. The City of Phoenix says: "Water pressure greater than 80 psi requires action by the home or business owner as it can damage your water pipes and appliances." Phoenix "requires that customers install a pressure regulator (pressure reducing valve) on the customer's side of the water meter to ensure that the water pressure does not exceed 80 psi in the home or business." A regulator that has worn out can let pressure creep up over time, so a house that was quiet for years can start squealing. What home water pressure should be explains the healthy range, and signs your pressure regulator is going bad lists what failure looks like. If pressure is fine and the squeal is at the water heater rather than the faucets, see why a water heater screeches or whines.

A squeal is a warning, and it usually gets louder as the part wears or the scale builds. Sorting it out early keeps a small repair small. Here is the fast version of everything above, in the order that rules out the easy causes first.

1. 1Note which faucet, which handle position, and whether it is hot, cold or both.
2. 2Open the angle stops fully.
3. 3Remove the aerator and run the water.
4. 4Try another faucet in the house.
5. 5Take a pressure reading at an outdoor spigot with a screw-on gauge.

The results narrow it down. Noise only in one handle position means a cartridge or washer. Noise gone with the aerator off means the aerator. Noise at every fixture means pressure or velocity.

Replacing a cartridge or cleaning an aerator is a reasonable do-it-yourself job with the water shut off at the fixture. Call a plumber if the shutoff valves will not turn or will not close, a valve drips from the stem when you move it, the noise continues after you have cleaned and replaced the parts, or the pressure reading is high. Forcing an old shutoff valve is how a small squeal becomes a leak under the sink.

HQ Plumbing & Air is licensed and insured, and we give free estimates and upfront pricing before work begins. If a faucet repair turns up a leak that will not stop, we handle emergencies 24/7.