How a Faucet Works: Cartridge, Ball, and Compression Types

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Every faucet does the same job through a different mechanism inside. The handle you push, lift, or twist is just a lever. What actually starts and stops the water is a valve hidden in the faucet body, and there are four common designs: compression, ball, cartridge, and ceramic disc. Knowing which one is sitting under your handle tells you why your faucet behaves the way it does, why it eventually fails, and what gets replaced when it does.

This guide is the anatomy lesson, not the repair. It explains how each valve seals and what moving the handle does to the parts inside. It does not diagnose a specific drip, walk through a fix, or cover the aerator screen at the tip of the spout, which is a separate part entirely. Once the mechanism makes sense, the diagnosis and repair guides in this cluster have something solid to build on.

The Four Faucet Valve Types and How Each One Seals

A faucet controls water in one of two ways: by pressing a soft part against a hard surface, or by sliding hard parts past each other. That single distinction sorts all four valve types.

Compression faucets use the first method. A rubber or silicone washer gets squeezed against a metal seat to block the water, the same way a cork seals a bottle. Everything that came later is some version of the second method, often called washerless because it stops relying on a soft part that crushes and wears. Ball, cartridge, and ceramic-disc faucets all move solid components so that ports either line up to let water through or slide out of line to shut it off.

Here is the quick map before the detail:

  • Compression: a washer presses down onto a seat. Two handles, oldest design.
  • Ball: a slotted ball rotates over spring-loaded seats. One handle, rounded cap.
  • Cartridge: a single insert moves up, down, and side to side inside a sleeve. One or two handles.
  • Ceramic disc: two polished ceramic plates slide across each other. Usually one handle.

The washer-versus-washerless split is the reason the newer types last longer and shut off more cleanly. A soft washer hardens and deforms with use, so a compression faucet tends to drip as it ages. The harder sliding surfaces in the other three resist that kind of wear, which is why they came to dominate.

Inside a Compression Faucet: Rubber Washers and Seats

A compression faucet shuts water off by screwing a washer down tight against a seat, and it is the only common type that does the job this way. Each handle threads onto a stem, and the bottom of that stem holds a small rubber or silicone washer. Turn the handle clockwise and the stem screws down, pressing the washer against a machined ring called the valve seat until the opening is sealed and the flow stops. Turn the handle the other way and the stem lifts, the washer pulls back off the seat, and water passes.

This is why a compression faucet always has two handles, one for hot and one for cold. Each handle drives its own independent stem and washer, so there is no mixing inside the body. The hot and cold streams meet only after they leave their separate valves. It is also why these handles need a firm, multi-turn twist to shut off fully, since you are physically compressing a washer rather than flipping a lever.

The design is simple and cheap, which is exactly why it shows up in older homes and on utility sinks. The trade-off is the washer. Rubber and silicone harden, flatten, and tear over time, and a worn washer no longer seats flat. The valve seat itself can also corrode or pit, so even a fresh washer cannot seal against it. That combination is the classic reason a two-handle faucet starts to drip from the spout. The how-to-tell and the repair for that drip live in their own guides; here the point is only that the failure traces back to a soft part being crushed against a hard one thousands of times.

Inside Ball, Cartridge, and Ceramic-Disc Faucets

These three are the washerless designs, and they share a common idea: instead of crushing a washer, they line up openings in moving parts to let water through, then slide those openings out of register to stop it. They differ in the shape of the moving part.

A ball faucet uses a slotted metal or plastic ball seated in the faucet body. As you move the single handle, the ball rotates, and holes drilled through it line up with the hot and cold inlet ports underneath. Spring-loaded rubber seats press up against the ball to keep the seal tight, and a cam and packing assembly holds the ball in position. Tilting the handle up and down changes how much the ports overlap, which sets the volume, while swiveling it side to side changes the mix of hot and cold. The springs and seats are the parts that wear, since they are the only soft components left, and a rounded dome-shaped cap over a single handle is the usual tell for this type.

A cartridge faucet replaces all of that with one sealed insert that drops into a sleeve in the faucet body. The handle connects directly to the top of the cartridge. On a single-handle model, lifting the handle up and down opens and closes the flow, and rotating it left and right blends hot and cold. The cartridge has ports along its body that align with the inlets as it moves, controlling both volume and temperature in one part. Cartridge faucets come as single-handle or two-handle units, and on a two-handle cartridge faucet each side has its own smaller cartridge that simply opens and closes that stream. The whole cartridge is meant to be pulled and swapped as a unit when it wears.

A ceramic-disc faucet, often grouped as a kind of cartridge, controls water with two hard ceramic discs. One disc is fixed in the housing and the other is attached to the handle and moves over it. Each disc has ports cut through it, and as the moving disc slides across the fixed one, the ports either align to pass water or offset to block it. The discs are polished so flat that they seal against each other almost on contact, with no rubber washer involved at all. That hard-on-hard sealing is why ceramic-disc valves are prized for resisting drips and lasting a long time, and many run for years without service.

How to Tell Which Valve Type You Have Without Taking It Apart

You can usually narrow down your valve type just by reading how the handle behaves, before you remove a single screw. The handle count and the way it moves are the strongest clues.

Start with how many handles there are:

  • Two separate handles, each needing several firm turns to shut off: almost always a compression faucet, especially on an older or utility sink. If it has two handles but each one is a quick quarter-turn lever rather than a multi-turn twist, it is more likely a two-handle cartridge or ceramic-disc design.
  • One handle: a ball, cartridge, or ceramic-disc faucet. The next clues separate these three.

Now read the single handle’s motion and feel:

  • A single handle under a distinct rounded, dome-shaped cap, with a slightly loose or wobbly feel as it swivels, points to a ball faucet.
  • A single handle that lifts straight up to turn on and rotates side to side for temperature, with a smooth and fairly stiff travel, points to a cartridge or ceramic-disc faucet. A very smooth, almost frictionless glide with a crisp stop often signals ceramic disc specifically.

A few outside hints help confirm it. A brand name on the handle or spout narrows the field, since some makers favor particular valve types, and the model often appears under the handle or on paperwork that came with the faucet. The faucet’s age matters too: a valve in a home from the 1970s or earlier is far more likely to be compression, while a faucet installed in recent decades is usually cartridge or ceramic disc. None of this requires tools or shutting off the water. You are reading behavior, not parts.

Why the Valve Type Decides How a Faucet Fails and Gets Repaired

The valve type is the single fact that predicts both how a faucet fails and what fixing it involves, because each design wears at its own weak point. Match the symptom to the mechanism and the rest follows.

A compression faucet fails at the washer and the seat. The soft washer flattens and the seat corrodes, so these faucets tend to develop a spout drip as they age, and the repair is at the washer-and-seat level. A ball faucet fails at its springs and rubber seats, the only soft parts left, so its leaks usually come back to those small components and the cam that holds the ball. A cartridge faucet concentrates the wear in the cartridge itself, which is why the standard fix is to pull the whole cartridge and seat a new one rather than rebuild it piece by piece. A ceramic-disc faucet has the fewest wear points, since the discs are extremely hard, so it leaks least often, and when it does the cause is usually grit caught between the discs, a cracked disc, or a worn inlet seal rather than a crushed washer.

This is also why a part bought for one valve type will not fit another. A compression washer means nothing to a cartridge faucet, and a Moen cartridge will not seat in a Delta ball body. Identifying the valve type first is what keeps you from buying the wrong repair part. The actual diagnosis of a specific drip and the step-by-step repairs branch off from here into their own guides, each one organized around the valve family this overview just laid out.

One practical note on flow while we are inside the faucet. The valve sets how the water is controlled, but how much water comes out is capped separately by federal and efficiency standards. Federal rules limit faucets to 2.2 gallons per minute at 60 psi, and EPA WaterSense labeled bathroom faucets go further, at a maximum of 1.5 gallons per minute at 60 psi while still delivering at least 0.8 gallons per minute at 20 psi. That ceiling is built into the faucet regardless of which of the four valves is doing the sealing.

Frequently Asked Questions

What are the four types of faucet valves?
Compression, ball, cartridge, and ceramic disc. Compression faucets press a rubber washer against a seat to stop water. Ball, cartridge, and ceramic-disc faucets are washerless, meaning they line up ports in moving parts instead of crushing a washer. The washerless types generally last longer and drip less.

How can I tell what kind of faucet I have without disassembling it?
Read the handle. Two handles that each take several firm turns to shut off usually mean a compression faucet. One handle under a rounded dome cap suggests a ball faucet. One handle that lifts up and swings side to side with a smooth, stiff feel suggests a cartridge or ceramic-disc faucet. Age and brand markings help confirm it.

What is a washerless faucet?
A faucet that does not use a soft rubber washer to seal. Ball, cartridge, and ceramic-disc faucets all control water by moving hard parts so that openings either align to pass water or offset to block it. Because there is no washer being crushed flat, these designs resist the wear that makes older compression faucets drip.

Why does my two-handle faucet drip but a single-handle one rarely does?
Two-handle faucets are usually compression types that seal with a rubber washer pressed onto a metal seat. The washer hardens and the seat corrodes with use, so they drip as they age. Single-handle ball, cartridge, and ceramic-disc faucets seal with harder sliding parts that wear more slowly, so they tend to drip less often.

Is a cartridge faucet the same as a ceramic-disc faucet?
They are closely related and ceramic-disc valves are often sold as a type of cartridge, but the sealing parts differ. A standard cartridge moves a single insert with ports inside a sleeve, while a ceramic-disc valve seals by sliding two polished ceramic plates across each other. Ceramic-disc designs are known for being especially durable and drip-resistant.

This article is general information about how faucet valves work and is not professional or safety advice. For diagnosing or repairing a specific faucet, follow the manufacturer’s guidance for your model or consult a licensed plumber.

Sources

  • U.S. Environmental Protection Agency, WaterSense, Bathroom Faucets (WaterSense labeled lavatory faucets use a maximum of 1.5 gpm at 60 psi and at least 0.8 gpm at 20 psi). https://www.epa.gov/watersense/bathroom-faucets
  • U.S. Department of Energy, Federal Energy Management Program, Best Management Practice #7: Faucets and Showerheads (federal maximum faucet flow rate of 2.2 gpm at 60 psi). https://www.energy.gov/femp/best-management-practice-7-faucets-and-showerheads
  • Delta Faucet, Ball Valve Repair Kit (single-handle ball faucet: rotating ball with ports, spring-loaded seats, and a cam assembly that seal against the ball). https://www.deltafaucet.com/parts/product/RP77763.html
  • Moen, Model 1225 One-Handle Replacement Cartridge (single-handle cartridge controls volume by raising and lowering the handle and temperature by rotating it side to side, blending hot and cold inside the cartridge). https://www.moen.com/products/Moen/Moen-One-handle-Replacement-Cartridge/1225
  • American Standard, What Is a Ceramic Disc Valve (two polished ceramic discs, one fixed and one moving, with ports that align to control flow and temperature; durable, washerless sealing). https://www.americanstandard-us.com/blogs/about-bathroom-sink-faucets/what-is-a-ceramic-disc-valve

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