11 · MIXER TAPS · posted 6 Oct 2026

What actually happens when you lift your tap lever?

In a conventional single-lever cartridge, a fixed ceramic disc has a hot port and a cold port. A second disc sits on top, and the lever moves it.
Lift the lever and the top disc slides, uncovering both ports together. That sets the flow.
Swivel it and the disc rotates, so one port opens wider while the other narrows. That sets the temperature.
The discs are lapped so flat, no washer is needed between them. One patent specifies a maximum shape defect of two light fringes (helium light, 0.589 µm).
Ball-type mixers work differently: a ball with a channel pivots in a socket. That design traces to Landis Perry's 1945 patent (granted 1952), not to Al Moen's separate single-handle faucet, which is often confused with it.

Line by line

Every claim, with its source.

Every spoken or on-screen factual claim is listed here with the source wording it rests on. Sources were fetched on 2026-10-01.

Shot	Claim as spoken or shown	Source and verbatim support
hook	"Two ceramic discs, each with holes."	US7318450B2: a "base disk" "crossed by two intake ports" and a "mixing disk" that moves over it. US5150737A: "Angular displacement of the mobile disc relative to the fixed disc progressively superposes the openings". Kerox K-45 P datasheet: "Material: AL2O3" (alumina ceramic).
lever	"The lever moves a top disc across a fixed one, with a hot port and a cold port."	US7318450B2: base disk "crossed by two intake ports...which can be connected respectively to a cold water feed duct and to a hot water feed duct"; mixing disk "can move with respect to the base disk along a direction that is parallel to the coupling plane...and can rotate about an axis that is perpendicular to said coupling plane".
flow	"Lift, and the top disc slides. It uncovers both ports. That's your flow."	US7318450B2: "by means of the translational motion, the mixing disk varies the passage sections of the intake ports...keeping their ratio constant so as to vary the flow-rate". (Lever lift = translation: the conventional two-motion cartridge.)
temp	"Swivel, and it rotates. One port opens wider, the other narrows. That's your temperature."	US7318450B2: "by means of the rotary motion the mixing disk varies the ratio between the passage sections of the intake ports...accordingly varying the ratio between hot water and cold water". On screen the "% HOT" readout is the computed circle-overlap area ratio, not a measured temperature.
seal	"No washer between them."	US5150737A: "the flatness of these ceramic discs and their smoothness are sufficient for the contact between their surfaces to provide the necessary sealing". US4651770A: discs "can slide against one another to selectively seal liquid under pressure". MadeHow: "Unlike cartridges that use rubber in the waterway, ceramic discs are lapped and polished to a degree of flatness that can only be measured in light bands."
seal	"The discs are lapped flat to about a wavelength of light." On screen: "2 LIGHT FRINGES MAX, HELIUM LIGHT, 0.589 µm, ONE PATENT'S SPEC".	US5150737A: "maximum shape defect is two interference fringes--helium emission ray, i.e. 0.589 um". US4651770A: "lapped and honed to provide extremely flat valving surfaces". "About a wavelength" is our plain-words paraphrase of two fringes at 0.589 µm (about 0.6 to 1.2 µm depending on fringe convention). A single patent's specification, not an industry standard.
ball	"A ball with a channel pivots in a socket."	US2592062A (Perry): "a spherical valve element universally pivotal in said socket", with "a single recess" communicating with the inlet ports and the outlet port.
ball	"Landis Perry filed that in 1945." On screen: "PERRY · FILED 1945".	US2592062A, Mixing valve, inventor Landis H. Perry, filed 21 Aug 1945, granted 8 Apr 1952. MadeHow: "Landis H. Perry created the first ball valve design in 1945, receiving a patent in 1952."
payoff	"Slide for flow. Turn for mix."	Summary of flow and temp (US7318450B2).

What the drawing simplifies

The top-down view is a schematic of the principle. Port positions, disc sizes and the round mixing chamber are illustrative; real cartridges use kidney-shaped cavities and a third (outlet) port in the base disc. The section view routes the mixed water out through the top for simplicity. Labelled "SCHEMATIC · NOT TO SCALE".
The hot and cold bars are computed from circle-circle overlap areas of the chamber and each port (lens formula) and assume equal supply pressure. They show the principle, not measured flow.
The section is a cut through both port centres; the swivel is not visible there (only the chamber position changes).
The fringe picture on seal is a cartoon of light fringes; real fringes are not like this, and the discs' flatness is far too small to draw to scale. The caption on screen says "fringes exaggerated".
The ball is drawn as a section with inlets at equal angles and one recess arc; Perry's patent has two lever axes (blend and volume) and only the blend axis is animated. The overlap bars for the ball are arc-overlap fractions.
Cartridges also contain rubber seals elsewhere (around the housing); the reel claims only that there is no washer between the two discs.

Checked, and cut

"Al Moen invented the ball faucet": false mix-up. The ball mixer is Perry's 1945 patent (granted 1952), developed by Delta. Moen's single-handle faucet (first sold late 1947) is a different design (encyclopedia.com: "a cylindrical design with a piston action"). Not spoken; corrected in the caption.
"Moen invented the single-handle mixer": Perry filed a single-lever ball mixer in 1945 too, so "first" is contestable. Not used.
Any flatness in nanometres, "perfectly flat" or "atomically flat": no source.
Cartridge lifetime figures (American Standard "1.5 million uses"): marketing claim. Not used.
KWC US5341845A (rotation-only cartridge): real, but a different motion scheme; the caption says "conventional cartridge".
Kerox K-45 P numbers (25 degree opening, 110 degree mixing angle, 28.2 l/min): verified, unused.

Sources

US Patent 7,318,450, "Mixing cartridge for single-lever mixing faucets" (Carlo Nobili). patents.google.com/patent/US7318450B2
US Patent 5,150,737, "Ceramic discs for taps and taps equipped with such discs". patents.google.com/patent/US5150737A/en
US Patent 4,651,770, "Ceramic disc faucet valve" (Speakman). patents.google.com/patent/US4651770
US Patent 2,592,062, "Mixing valve" (Landis H. Perry, filed 1945). patents.google.com/patent/US2592062A/en
Kerox K-45 P cartridge datasheet. noelsplumbingsupply.com/wp-content/uploads/2019/02/Kerox-K-45-P-Specifications.pdf

Found an error?

Tell us at hello@workingshown.xyz or in the comments. We check it against the sources, pin the correction, fix the caption, and log it on the corrections page.