# Water tap > Opening and shutting a flow of water by hand - Date: c. 40 - Era: Antiquity - Domain: [Building & Cities](https://lastcodex.org/en/domains/building/) - Rebuild stage: III (Crafts & cities) - Difficulty: 2/5 - URL: https://lastcodex.org/en/inventions/water-tap/ A tap lets water out of a pipe or a vessel and stops it again: a part inside closes the passage, either a pierced plug turned by a quarter turn or a soft washer screwed down onto a seat. The oldest taps known for certain are Roman and bronze: one from the ships of the emperor Caligula on Lake Nemi (37–41 CE), others from Pompeii, buried in 79 CE; a bucket with a tap above a basin still makes a simple handwashing station. ![Water tap · Opening and shutting a flow of water by hand](https://lastcodex.org/_astro/plate.Bd6wCz6__Z1UJcER.webp) ## Legend 1. Crosshead handle 2. Threaded spindle 3. Gland 4. Jumper and washer 5. Seat 6. Spout ## What it is ![A lidded bucket on a wooden stand with a small tap near its bottom, a basin underneath and a bar of soap on the stand](https://lastcodex.org/_astro/v1.B83jfDqA_ZgIQbg.webp) _A bucket with a tap over a basin is enough for washing hands under running water._ A tap, or faucet, is a valve that a person opens and closes by hand to draw water from a pipe or a vessel. Water in a supply pipe is under pressure, and the tap holds it back until someone turns the handle. Opening it part of the way gives a thin stream, opening it fully a strong one. The same part serves at the end of a mains pipe and on a vessel filled by hand. On a sink it delivers water to drink, cook and wash with. Where there is no piped water, a bucket fitted with a tap and set above a basin gives a stream of running water for washing hands. The WHO and UNICEF count such buckets among handwashing stations, together with sinks, basins and tippy-taps. ## How it works Every tap puts a movable part across the flow. In the Roman tap, a bronze cylinder pierced right through turns in a body with a branch on each side. When the hole lines up with the branches, water passes; a quarter turn of the key sets the solid part of the cylinder across them, and the flow stops. The screw-down tap works differently. Water comes in through the pipe and rises from below to a round seat inside the body. Above the seat sits the jumper, a small disc carrying a soft washer. Turning the handle screws the spindle down through the fixed headpiece of the tap, and the spindle presses the washer onto the seat, which closes the passage. Turning the other way lifts the spindle, the washer leaves the seat and water flows over it to the spout. Because the spindle moves along a thread, the tap closes gradually, and a small turn gives fine control of the flow. Where the spindle leaves the body, a gland, a nut squeezing a packing round the spindle, stops water from leaking up past it. The washer is the part that wears: once it is cut or hardened, the tap drips even when closed, and replacing the washer cures it. Modern taps often use a cartridge instead, in which two ceramic discs with openings slide against each other, or a single lever that mixes hot and cold water. ## How to do it ![A bucket cut open to show the body of a tap passing through its wall, with a rubber washer on each side of the wall, a knurled back nut inside and a lever handle and spout outside](https://lastcodex.org/_astro/v2.DrzTAIpv_LOES.webp) _The rubber washers on both sides of the wall, pressed by the back nut, keep the bucket from leaking round the tap._ A handwashing station uses a ready-made tap. You need a plastic bucket of about 20 litres with a lid, made for food or water, a plastic tap with a threaded body, two rubber washers and a back nut, a stand that holds the bucket at about waist height and a basin or bucket to catch the used water. Mark a point about 5 cm above the bottom of the bucket and drill a hole the size of the thread of the tap there, with the bucket held firmly and safety glasses on. Smooth the edge of the hole. Push the tap through from outside with a washer on it, put the second washer and the back nut on from inside and tighten them by hand, then a little more, until the washers are pressed against the wall. Fill the bucket with clean water and check that no drop forms round the tap. Set the bucket on its stand, the basin underneath and soap beside it. Label the bucket as not for drinking. Empty, wash and refill it regularly, and empty the basin of used water often, away from where people walk. Never fill it with hot water, which can scald. ## History and evolution The oldest taps known for certain are Roman. The first of the two ships that the emperor Caligula (37–41 CE) had built on Lake Nemi, south of Rome, carried lead water pipes stamped with his name and a large bronze plug tap, finely turned and well preserved, recovered when the level of the lake was lowered by pumping from 1928. Bronze taps from Pompeii, buried by the eruption of Vesuvius in 79 CE, have a body with two side branches joined to the pipes, a cylinder pierced through that turns inside it, and a square or ring-shaped key to turn it. One is still soldered into a length of lead pipe. The Science Museum in London holds other Roman bronze taps dated between the first century BCE and the third century CE. They were made in standard sizes, matched to the pipe sizes set out by Frontinus, who ran the water supply of Rome at the end of the first century. ![A Roman bronze tap cut open on a stone slab: a body with two opposite side branches, a tapered plug seated in it and pierced by a hole lined up with them, its square head standing out at the top, beside a ring-shaped key](https://lastcodex.org/_astro/v3.Cp3Kjugd_2fXV13.webp) _In a Roman tap, a quarter turn of the key moves the hole in the plug in or out of line with the pipes._ Until the middle of the twentieth century, sinks usually had separate taps for hot and cold water. After scalding his hands in 1937, the American Al Moen designed a tap with a single handle that mixes the two, first sold in San Francisco in 1947. Ceramic discs later replaced the washer in many taps. Taps also serve where there are no pipes. In Ghana, the scientist Veronica Bekoe developed a bucket with a tap for washing hands in medical laboratories that had no running water, around 1990. Called the Veronica bucket, it spread to clinics, restaurants and homes. ## Key facts - Oldest taps known: Roman bronze plug tap from Caligula's ships on Lake Nemi, 37–41 CE - Roman tap: A pierced cylinder turned a quarter turn by a key - Screw-down tap: A washer pressed onto a seat by a threaded spindle - Single-handle mixer: Sold by Al Moen from 1947 ## Requires - [Bronze](https://lastcodex.org/en/inventions/bronze/): Copper and tin, harder together (c. 3,300 BCE) - [Aqueduct](https://lastcodex.org/en/inventions/aqueduct/): Water carried by gravity alone (c. 690 BCE) - [Leather Tanning](https://lastcodex.org/en/inventions/leather-tanning/): Raw hide, oak bark and months in pits (c. 1,500 BCE) ## Sources - [Enciclopedia Italiana (1934), Lago di Nemi: bronze plug tap and Caligula's lead pipes from the first ship](https://www.treccani.it/enciclopedia/lago-di-nemi_(Enciclopedia-Italiana)/) - [Osservatorio Colli Albani, Le navi di Nemi](https://www.osservatoriocollialbani.it/2017/05/24/le-navi-di-nemi/) - [Homo Faber, Science and technology of water: hydraulic valves (Pompeii, 1st century AD)](https://mostre.museogalileo.it/homofaber/en/technology/3-science-and-technology-of-water/3-1-hydraulic-valves.html), Museo Galileo, Florence - [Ancient garden from Babylon to Rome: bronze tap from Pompeii](https://brunelleschi.imss.fi.it/giardinoantico/egar.asp?c=24653), Istituto e Museo di Storia della Scienza, Florence - [Water taps in the collection (Roman bronze taps, 100 BCE–300 CE; later taps)](https://collection.sciencemuseumgroup.org.uk/search/object_type/tap-%252d-water), Science Museum Group - [How is TAP assembled (ME371 course project)](https://home.iitk.ac.in/~amit/courses/371/gaurava/assembly.html), Indian Institute of Technology Kanpur - [Faucet (How Products Are Made)](https://www.encyclopedia.com/science-and-technology/technology/technology-terms-and-concepts/faucet), Gale / Encyclopedia.com - [A burst of hot water leads to Al Moen's invention of the single-handle faucet](https://www.designerstoday.com/kitchen-bath/a-burst-of-hot-water-leads-to-al-moens-invention-of-the-single-handle-faucet-archive), Designers Today - [Handwashing Facility Worksheet (with the WHO/UNICEF JMP definition of a handwashing station)](https://www.unicef.org/media/75706/file/Handwashing%20Facility%20Worksheet.pdf), UNICEF - [What is a Veronica Bucket?](https://thp.org/news/what-is-a-veronica-bucket/), The Hunger Project - [Veronica bucket inventor seeks government support for patenting](https://www.graphic.com.gh/news/general-news/veronica-bucket-inventor-seeks-government-support-for-patenting.html), Graphic Online (Ghana) Fact-checked on 2026-10-19. --- The Last Codex · https://lastcodex.org/en/inventions/water-tap/ · © The Last Codex. 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