Kitchen Faucet Parts: Everything You Need To Know – This Old House

If your kitchen faucet has ever dripped at 2 a.m. like it’s auditioning for a suspense movie, you already know the truth: a faucet is basically a tiny plumbing orchestra. When one little part gets cranky, the whole performance turns into a squeaky solo.

This guide breaks down the most important kitchen faucet parts, what they do, how they fail, and how to identify what you actually need before you buy the wrong piece (and create a special drawer full of “maybe someday” parts). You’ll also learn the common valve styles, what’s inside single-handle vs. two-handle faucets, and how to troubleshoot leaks and low flow with confidence.

Kitchen Faucet Anatomy: The Parts You’ll Hear About Most

Most kitchen faucetsno matter how fancyshare the same core components. The difference is mostly in how they package them (and how much they charge for “European-inspired minimalism”).

1) Spout

The spout is the curved “neck” that delivers water into the sink. On many faucets, the spout swivels and seals with one or more O-rings at its base. If you see water pooling around the base when the faucet runs, spout O-rings are prime suspects.

2) Handle (and Set Screw)

The handle is your control leversingle-handle faucets mix hot and cold together, while two-handle faucets separate them. Many handles are held in place with a small set screw (often hidden under a cap). A loose handle doesn’t just feel annoyingit can also stop the valve from closing properly, leading to drips.

3) Faucet Body

The body is the main housing that holds internal parts. It’s the “engine block” of the faucet. Inside, you’ll find the valve systemcartridge, ball, or discplus seals and hardware that keep everything watertight.

4) Cartridge (or Valve Assembly)

The cartridge is the most commonly replaced internal part in modern faucets. It controls water flow and temperature mixing. When cartridges wear out, you may get dripping, stiff operation, temperature swings, or weak flow.

Some faucets use a ball valve assembly (common in certain single-handle designs), while others use ceramic disc cartridges known for durability and smooth movement.

5) Aerator

The aerator screws onto the tip of the spout. It adds air to the water stream to reduce splashing, and it can also restrict flow for efficiency. If your faucet suddenly has low flow, sputters, or sprays sideways like a naughty garden hose, the aerator is often clogged with sediment.

6) Seats and Springs (Common in Ball-Valve Faucets)

In some faucet designs, especially ball-valve types, small seats and springs create a seal. If these wear out, you can get persistent dripping even when the valve looks fine. They’re small, easy to lose, and suspiciously talented at bouncing into unreachable places.

7) O-Rings, Washers, and Gaskets

These are the unsung heroes. O-rings seal moving parts like spouts and cartridges. Washers and gaskets seal stationary connections. When they harden, crack, or flatten over time, leaks follow.

8) Sprayer Head (Pull-Down / Pull-Out Faucets)

If you have a pull-down or pull-out faucet, you also have a sprayer head with its own internal screen, seals, and sometimes a flow restrictor. Mineral buildup can affect spray modes and pressure.

9) Diverter

The diverter is what switches water from the main spout stream to the sprayer (or between spray patterns). If you press the sprayer button and water still pours from the spout like it didn’t get the memo, the diverter may be worn or clogged.

10) Hose, Weight, and Quick-Connect Fittings

Pull-down faucets use a flexible hose under the sink, often paired with a weight that helps the sprayer retract. Many modern faucets use quick-connect fittingsconvenient, but they must be fully seated to prevent leaks.

11) Mounting Hardware: Deck Plate, Escutcheon, and Mounting Nuts

The deck plate (sometimes called an escutcheon) covers extra holes in the sink or countertop. Under the sink, mounting nuts, brackets, and washers keep the faucet tight. If the faucet wobbles, the issue is often herenot in the water valve itself.

12) Supply Lines and Shutoff Valves (Not “Faucet Parts,” But Still Part of the Story)

Under the sink, flexible supply lines connect to shutoff valves. A leak at a connection point might not be the faucet at allit could be a supply line fitting, a worn compression seal, or a valve that needs service.

Valve Types: What’s Inside Your Faucet (and Why You Should Care)

When people say “replace the cartridge,” they’re often describing the whole valve mechanism. But faucets don’t all work the same way. Knowing your valve type helps you buy the correct replacement and avoid turning a quick fix into a weekend project with emotional damage.

Compression Valves (Classic Two-Handle Style)

Compression faucets typically use rubber washers pressed against a valve seat. They’re common in older two-handle faucets. Symptoms include dripping from the spout that improves or worsens based on how tightly you crank the handle. (If you have to “Hulk tighten” the handle to stop a drip, something’s worn.)

Cartridge Valves (Common, Simple, Reliable)

Cartridge-style faucets can be single- or two-handle. They use a cartridge that moves up/down or rotates to control flow. These are usually straightforward to serviceif you can identify the correct cartridge model.

Ball Valves (Often Single-Handle)

Ball-valve faucets use a rounded ball mechanism plus seals like seats and springs. They can work well, but they have more small parts than some other styles.

Ceramic Disc Valves (Smooth Operator)

Ceramic disc faucets use very hard ceramic discs to control flow. They’re known for durability and smooth handle action. When they fail, it’s often due to debris or worn seals rather than the ceramic itself.

How to Identify the Exact Parts You Need

Here’s the hard truth: “universal cartridge” is sometimes real, but it’s also sometimes marketing poetry. The safest path is identification first, shopping second.

Step 1: Find the Brand and Model

• Check the faucet base, underside of the handle, or under-sink supply lines for tags or labels.
• Look for a model number in the paperwork or installation manual if you still have it.
• If you can’t find it, take clear photos from multiple angles, including the handle and spout profile.

Step 2: Identify the “System” You’re Repairing

Is it a spout leak (O-rings), a handle leak (cartridge/seals), low flow (aerator/screen), or a sprayer issue (diverter/hose/head)? The symptom tells you where to focus.

Step 3: Remove the Old Part and Match It

For cartridges, the gold standard is removing the old one and matching itsame length, stem shape, and tabs. Even within one brand, cartridges can vary by series and year.

Common Kitchen Faucet Problems (and Which Parts Usually Cause Them)

Problem: Dripping from the spout

Likely culprits: cartridge, seats and springs (ball-valve), worn washers (compression style), mineral buildup preventing full closure.

Example: You turn the faucet off, but a slow drip continues. If tightening the handle doesn’t help, the valve seal is worn or debris is stuck in the valve path. Replacing the cartridge (or seats/springs) often resolves it.

Problem: Water leaking from under the handle

Likely culprits: cartridge seals, packing nut area, O-rings, worn gasket.

Example: You see water around the handle base when the faucet runs. That’s often a worn seal around the cartridge stem. Fixing it typically involves replacing O-rings or the whole cartridge.

Problem: Water pooling around the faucet base

Likely culprits: spout O-rings, loose mounting hardware, worn gasket under the deck plate.

Example: Everything looks fine until you move the spout side-to-side, and suddenly you’re hosting a tiny lake. Spout O-rings may be worn and need replacement plus a small amount of plumber’s grease.

Problem: Low flow or weird spray pattern

Likely culprits: clogged aerator screen, debris in sprayer head screen, partially closed shutoff valve, kinked hose.

Example: Flow is weak on both hot and cold. First stop: aerator. Unscrew and rinse it. If you have a pull-down sprayer, check the spray head screen too.

Problem: Sprayer won’t switch modes (or won’t return)

Likely culprits: diverter, sprayer head mechanism, hose issues, retraction weight snagging.

Example: The sprayer button sticks or the head doesn’t dock smoothly. Look under the sink: the weight may be catching on a cleaning bottle (the most common “hidden villain” in modern kitchens).

DIY Repair Basics: Smart Moves Before You Take Anything Apart

Turn off the water (yes, really)

Shut off hot and cold valves under the sink. If those valves are stiff or unreliable, shut off the main water supply. Then open the faucet to relieve pressure.

Protect your sink and your sanity

• Plug the drain so small parts don’t disappear.
• Use a towel or rubber mat to protect finishes.
• Lay parts out in the order you remove them.

Use the right tools

A basic kit might include an adjustable wrench, Allen keys, screwdrivers, slip-joint pliers, and a strap wrench for delicate finishes. A flashlight is also importantbecause under-sink lighting is apparently designed by vampires.

Replacement Parts Shopping Tips (So You Don’t Buy the Wrong Thing)

Cartridges are not “close enough” parts

Match the exact cartridge whenever possible. Even small differences in stem shape or tabs can prevent proper seating and cause leaks.

Consider a repair kit instead of a single piece

For some faucet designs, kits that include seats, springs, cams, and O-rings can be more effective than replacing one part at a timeespecially when multiple seals have aged together.

Bring the old part (or detailed photos)

For O-rings and washers, measure carefully. For cartridges, bring the old one if you can. A photo plus a model number is the next best thing.

Don’t ignore water-efficiency upgrades

Many modern aerators are designed to reduce water use while maintaining a comfortable stream. If you’re replacing an aerator anyway, it’s a good moment to choose an efficient option that still feels strong for rinsing dishes.

When to Repair vs. Replace the Faucet

Repair is usually the move when:

• The faucet body is in good shape (no cracks, severe corrosion, or major pitting).
• The leak is clearly coming from a serviceable part (cartridge, O-rings, aerator).
• Replacement parts are readily available.

Replacement may make more sense when:

• The faucet is heavily corroded or the finish is failing badly.
• Parts are discontinued or unusually expensive.
• You’re already remodeling and want a different layout (like a pull-down sprayer or higher arc).

Maintenance That Actually Helps (Without Turning You Into a Faucet Influencer)

Clean the aerator periodically

Unscrew, rinse, and remove debris. In hard-water areas, soaking the screen in vinegar can help dissolve mineral buildup (rinse thoroughly afterward).

Keep the area under the sink organized

Pull-down hoses and weights need a clear path. If your sprayer won’t retract, it may be fighting a tangle of cleaning products and spare sponges.

Use plumber’s grease (sparingly) on O-rings

When replacing spout O-rings, a small amount of silicone-based plumber’s grease can improve sealing and reduce wear. Don’t use petroleum jelly unless the manufacturer says it’s compatible; some rubbers don’t love it.

Real-World Experiences: What People Learn the Hard Way About Kitchen Faucet Parts (Extra Notes)

Below are common, real-life experiences homeowners and DIYers run into when dealing with kitchen faucet partsshared here so you can skip the “trial,” keep the “learning,” and avoid inventing new words while kneeling on a cabinet hinge.

1) “It’s definitely the faucet!” (Spoiler: sometimes it’s the shutoff valve)

A classic under-sink mystery: you see water, you blame the faucet, you buy a cartridge, and… the leak continues. Often the drip is actually coming from a supply line connection or a tired shutoff valve packing nut. A quick test is to dry everything thoroughly, run the faucet, and watch where the first bead of water appears. Faucet leaks usually show up above the countertop (handle area, base, spout). Supply line and valve leaks appear below. It’s not glamorous detective work, but it saves money.

2) Aerators are tiny drama magnets

People expect big problems to have big causes. But low flow is frequently a clogged aeratorespecially after plumbing work, a water shutoff, or a local water main repair that shakes sediment loose. The “fix” can be as simple as unscrewing the aerator, rinsing out grit, and reinstalling it. The catch: some aerators use special keys, some are recessed “cache” aerators, and some have thread sizes that are not as universal as they look online. The practical lesson is to identify your aerator type before ordering, and keep the old one until the new one is installed and confirmed.

3) The “almost right” cartridge is the most expensive one

One of the most common experiences is buying a cartridge that looks nearly identicalsame brand, same basic shapeonly to discover it won’t seat, the handle won’t align, or the faucet drips worse than before. Cartridges can differ by millimeters, stem shape, or tab orientation. People often learn to bring the old cartridge to match it physically (or to rely on the faucet’s model number and parts diagram). If you’re stuck, taking multiple photos of the cartridge next to a ruler can prevent the “close enough” mistake.

4) Pull-down sprayers fail in surprisingly ordinary ways

When a pull-down faucet misbehaves, it’s tempting to assume something fancy broke. In reality, many issues are simple: the hose weight gets snagged on stored items, the quick-connect isn’t fully seated, or the sprayer head screen is clogged. A common experience is “the sprayer won’t retract” that turns out to be a detergent bottle blocking the weight. Another is “weak spray” that turns out to be mineral buildup in the sprayer head screencleanable in minutes. The lesson: before replacing parts, look under the sink and check the hose path.

5) O-rings: cheap parts, big payoff

When a faucet leaks at the base or around a swiveling spout, people often assume the whole faucet is failing. In many cases, it’s just worn spout O-rings. Replacing them can make the faucet feel brand new, and it’s usually inexpensive. The “real-world” catch is that O-rings must be the correct diameter and thickness, and some faucets require a specific material. Many DIYers learn to take the old O-ring to match it exactly, and to use a tiny amount of silicone plumber’s grease to help the spout rotate smoothly without chewing up the new seals.

6) Reassembly is where confidence goes to get tested

Another universal experience: disassembly feels great (“I am unstoppable”), then reassembly introduces doubt (“Why do I have one extra screw?”). The practical strategies people swear by include laying parts out in order, snapping quick photos during each step, and placing small screws in a cup so they don’t teleport away. Even if you’re not “a photo person,” a couple of pictures can be the difference between a 30-minute repair and a 3-hour puzzle.

7) The best faucet-part habit is knowing when to stop tightening

Over-tightening is a frequent DIY regret. Too much force can crack plastic retainers, strip threads, or distort washers so they leak. Many people learn the “snug plus a little” rule: tighten until secure, then a small additional turnespecially on compression fittings and plastic components. If a connection leaks, the fix is often reseating the washer or fitting, not cranking harder like you’re trying to win an arm-wrestling match with your plumbing.

The bottom line from these experiences: most kitchen faucet problems are fixable, and many are caused by small, affordable parts. The real trick is diagnosisfiguring out which component is actually failing before you replace half the faucet out of frustration.

Conclusion

Kitchen faucets aren’t mysteriousthey’re just busy. Once you understand the key kitchen faucet parts (cartridge, aerator, O-rings, diverter, hose, and mounting hardware), you can troubleshoot leaks and low flow like a pro, shop smarter, and keep your sink from starring in its own drip soundtrack. Whether you’re repairing a simple aerator clog or swapping a cartridge, the goal is the same: steady flow, solid seals, and a faucet that behaves like it pays rent.