TapClear

How does a tap work?
Nothing inside a tap pushes the water. The push comes from a tank on the roof, and the tap is only a gate. Slice open a brass tap, turn two ceramic discs, snap a valve shut and watch the pipe bang.

▶ Play with it  ·  Read the 60-second explainer  ·  Watch the 40-second video

In 60 seconds

1. A tap is a gate, not a pump. The water in the pipe is always under pressure. A tap only blocks the pipe and unblocks it. In a brass bib tap, a screw presses a rubber washer on to a hole called the seat. Packing round the spindle and PTFE tape on the thread stop water escaping anywhere else.
2. The push comes from height. In most Indian homes the pressure comes from an overhead tank. It depends only on how far the water surface is above the tap: P = ρ g h, about 0.1 bar for every metre. So the ground floor gets a strong flow and the top floor a weak one, unless the tank is raised or a pump is added.
3. The screw-down tap: many turns, one hard squeeze. Each turn of the handle moves the washer only about 2 mm, which is how a light twist becomes a tight seal. The flow rises quickly in the first turn and then levels off. When the washer wears, the tap drips: one drip a second is about 21 litres a day.
4. The ceramic disc: a quarter turn. Modern taps use two discs of alumina ceramic, polished so flat that water cannot pass between them. One is fixed and one turns. Line up their ports and water flows; a quarter turn later each port faces solid ceramic. Nothing is squeezed, so there is no washer to wear, but grit and limescale can ruin them.
5. Stop valves, and the bang in the pipe. A ball valve is a bored ball that turns a quarter turn. A gate valve is a wedge lifted by a screw. Shut a valve in an instant and the moving water piles up against it. The pressure jumps by density × wave speed × flow speed, and a wave bangs along the pipe: water hammer.
6. At the spout: air and less water. An aerator pushes the water through small holes, draws air in through side slots and mixes them through mesh. The stream feels full and does not splash, with less water. A rubber ring can hold the flow steady whatever the pressure, which is how taps earn star ratings.

Words worth knowing

Term	Meaning
Head	The height of the water surface above a tap. Each metre of head gives about 0.1 bar of pressure.
Seat and washer	The brass rim round the hole inside a tap, and the soft disc a screw presses on to it to stop the water.
Spindle	The threaded rod joined to the handle. One turn moves it about 2 mm, turning a light twist into a strong squeeze.
Ceramic disc cartridge	Two flat alumina discs with ports. A quarter turn slides the ports into or out of line.
Ball valve	A stop valve with a bored ball between PTFE seats. A quarter turn opens or shuts it.
Gate valve	A stop valve with a wedge that a screw lifts clear of the flow. Slow to work, clear when open.
Water hammer	The jump in pressure, and the bang, when flowing water is stopped suddenly. Joukowsky's rule: ΔP = ρ c v.
Aerator	An insert at the tip of the spout that mixes air into the water for a soft stream that uses less.
Flow rate	How much water comes out each minute. It depends on the pressure and on the narrowest opening on the way.

A short history

4,500 years from city wells and Roman bronze plugs to a ceramic disc in your kitchen and a tap in almost every home.

• 79 · The Roman bronze tap (Roman bronze workers, Pompeii, Italy)
• 1845 · The screw-down tap (Guest and Chrimes (the Chrimes brothers), Rotherham, England)
• 1937 · Air in the stream: the aerator (Elie Aghnides, USA)
• 1947 · One handle for hot and cold (Al Moen, Seattle, Washington, USA)
• 1954 · The ball faucet called Delta (Landis H. Perry and Alex Manoogian, Detroit, Michigan, USA)
• 1972 · Two ceramic discs replace the washer (American Standard and Ideal Standard (credit is shared), USA and Germany)
• 2010 · Water is declared a human right (United Nations General Assembly, New York, USA)
• 2019 · Har Ghar Jal: a tap for every rural home (Government of India (Jal Jeevan Mission), India)

The full story, with 27 moments, charts, people and 53 sources: glassbox.how/e/tapclear/history. The data lives in history.json.

Video and slides

Made with the Glassbox studio from this box's storyboard (window.glassbox.director). Free to reuse under CC BY 4.0.

File	What	Size
glassbox/reel.mp4	Reel / Short, with captions and soundtrack	1080×1920
glassbox/video.mp4	YouTube video, with captions and soundtrack	1920×1080
glassbox/slide-1…10.jpg	Instagram carousel	1080×1350
glassbox/thumb.jpg	YouTube thumbnail	1280×720
glassbox/cover.jpg	Share card and repo social preview	1200×630
glassbox/history-reel.mp4	“History in 10 moments” Reel / Short	1080×1920
glassbox/history-slide-*.jpg	History carousel	1080×1350
glassbox/post.json	Post copy and schedule used by the publish kit

Privacy

This box has no accounts and no ads, and it ships its own fonts and libraries. When you run it yourself it sends nothing anywhere. On glassbox.how, the site's /bar.js also loads Glassbox's analytics: Google Analytics to count visits (it asks first in the EU, UK and Switzerland, and stays off when your browser sends Global Privacy Control or Do Not Track) and ClickTrust to detect bots.

It remembers a few things in your own browser only, and never sends them anywhere:

Browser storage key	What it holds
tapclear.v1	Which chapters you have opened, your best quiz scores, and sound on or off.

Exactly what each one sees is at glassbox.how/privacy.

Licences

• Code: MIT. Use it, change it, ship it.
• Explanations, text, images and videos (glassbox.json, glassbox/): CC BY 4.0. Credit “Glassbox, glassbox.how/e/tapclear”.
• Third-party parts keep their own licences: three.js (MIT), Geist, Instrument Serif (SIL OFL 1.1).
• The Glassbox name and logo aren't covered by either licence. See the terms.

Found a mistake? Open an issue. Corrections happen in public.

Run it

It's plain HTML, CSS and JavaScript. No build step and no dependencies. Run locally, it contacts no other website.

python3 -m http.server 8000

Three.js and the fonts ship in vendor/ and fonts/, so it also works offline.

Then open http://localhost:8000.

How it's built

File	What
index.html, css/app.css	The page and its styles
js/app.js, js/stage.js, js/ui.js, js/kit.js	The shared Glassbox 3D engine: chapters, 3D stage, controls, quiz, video director
js/tap.js	TapClear's own physics and parts: head and pressure, flow through pipes and valve openings, water hammer, sliced (cut-away) geometry, flowing water particles, the brass bib tap
js/chapters/*.js	One file per chapter: the 3D model, controls, text, key terms, quiz and video scenes
glassbox.json	Title, question, explainer beats, key terms, browser storage and credits shown on glassbox.how
reel in each chapter	The storyboard the Glassbox studio records into short videos
glassbox/	The published video, slides, thumbnail and post copy
fonts/, vendor/three/	Self-hosted Geist and Instrument Serif (SIL OFL 1.1) and three.js (MIT)