Master Timeline of Water Heating

 

This page is the dated spine of Waterheaterhistory.com. The homepage is the map. This is the calendar.

Read it as one line from heated stones to heat-pump tanks. Each entry is a checkpoint, not a full article. When you want the story behind a date, open the page that owns it:

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• Ancient Origins for baths, floors, and hypocausts

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• Inventors and Pioneers for Maughan, Ruud, Kemp, and Bailey

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• Technology Evolution for how the machines changed

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• Company Histories for the factories

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• Heat Pump Inventors for the efficiency chapter

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• Technical Glossary when a word gets in the way

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How to use this timeline

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Start at the top if you want the whole arc. Jump to an era heading if you already know the century.

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Treat a patent date as the legal date, not always the first day someone built a prototype. Edwin Ruud designed his automatic storage heater in 1889. The U.S. patent issued on December 30, 1890. Both dates are true. They answer different questions.

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If a date or a credit is still thin, the notes at the bottom of this page say so. The timeline is updated when better evidence shows up.

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The eras on this page

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• Ancient & Pre-Modern — public heat, kitchen range boilers, and the first solar experiment

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• 19th Century: The Birth of Dedicated Water Heaters — the first machines built only to make hot water

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• 1900–1945 — electric units, glass lining, and wartime interruption

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• Post-War Expansion (1945–1980s) — tanks in ordinary houses

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• Efficiency Era & Modern Systems (1987–Present) — federal rules, tankless revival, and heat pumps

 

 

Ancient & Pre-Modern

 

c. 5000 BCE — Stone boiling

 

Long before anyone owned a tank, people heated rocks in a fire and dropped them into water. That method shows up in river valleys around the world. It is slow and messy. It is also the first clear way humans stored heat and then gave it to water. The longer account is on Ancient Origins.

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c. 2500 BCE — The Great Bath at Mohenjo-daro

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In the Indus Valley, builders made a huge brick tank with stairs and a drain. Whether the water was warmed is still unproven. The engineering is not. Public stored water already existed, thousands of years before a closet tank.

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c. 1000 BCE — Ondol floors in Korea

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A kitchen furnace sent heat through flues under a stone floor. The house itself became the radiator. That idea never really died. Later floor-heating systems still follow the same logic: put the fire in one place, move the heat under the people.

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Roman period (1st–4th centuries AD) — Hypocausts and public baths

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Rome did not invent hot water. It industrialized it.

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A furnace called a praefurnium pushed hot gases through a forest of brick piers under the floor and up flues in the walls. That system is the hypocaust. Large public and private baths used boilers and a steady supply of heated water. In some designs a bronze heater called a testudo — “tortoise” — sat over the fire and warmed the pool.

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This is one of the earliest large-scale approaches to hot water for bathing. Ruins at Pompeii, Herculaneum, and sites across North Africa still show the fireboxes, channels, and rooms. For who bathed there, and what a bathhouse was for, see Cultural & Social Impact. For the archaeological detail, see Ancient Origins and Ancient Early Baths.

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18th–early 19th century — Range boilers and water-backs

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Dedicated water heaters did not appear overnight. The in-between step sat in the kitchen.

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A water-back, also called a water jacket, was a cast-iron chamber built into the firebox of a coal, wood, or later gas cooking range. Water warmed while dinner cooked, then moved to a nearby storage tank. That tank was often called a range boiler.

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These systems gave a household a little stored hot water. The catch was simple: the stove had to be running. No fire, no heat. That is why range boilers belong on this timeline but are not yet the modern appliance. They are the last major batch-heat setup before Maughan’s Geyser and Ruud’s automatic tank. Technology Evolution places them in that transitional line.

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1767 — Horace-Bénédict de Saussure’s solar hot box

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In 1767 the Swiss scientist Horace-Bénédict de Saussure built an insulated box with glass covers. Sunlight went in.

 

Heat had a hard time getting back out. The box reached high temperatures.

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It was an experiment, not a product you could buy. It still matters. The same idea — glass, insulation, a dark surface that holds heat — sits inside Clarence Kemp’s 1891 Climax solar heater and William Bailey’s later Day and Night system. Solar water heating is not a 1970s add-on. The concept is on this timeline before the first household gas geyser.

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What comes next on this page

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The next heading, 19th Century: The Birth of Dedicated Water Heaters, is where the modern appliance starts:

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• 1868 — Benjamin Waddy Maughan patents the Geyser, the first instantaneous gas heater for a home

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• 1889–1890 — Edwin Ruud designs the first automatic storage-tank gas water heater in Pittsburgh

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• 1891 — Clarence M. Kemp patents the Climax, the first commercial solar water heater

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• 1897–1898 — Ruud founds his company and patents an improved automatic instantaneous heater

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• 1909–1910 — William J. Bailey’s Day and Night system splits the solar collector from indoor storage

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​19th Century: The Birth of Dedicated Water Heaters

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In 1868, Benjamin Waddy Maughan, a London painter, patented the first gas instantaneous domestic water heater that did not use solid fuel. Named the “Geyser,” cold water flowed through pipes heated by a gas burner at the base. The design had no flue to remove combustion gases and was therefore dangerous, yet it established the principle of on-demand (tankless) heating.

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1889–1890: Edwin Ruud, a Norwegian-American mechanical engineer working in Pittsburgh for the Fuel Gas and Manufacturing Company (associated with George Westinghouse), designs and patents the first automatic storage-tank gas water heater.

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• Design completed in 1889

• U.S. Patent 443,797 granted 30 December 1890

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The unit used a bottom gas burner controlled by a temperature-sensitive valve — the foundation of the modern automatic storage water heater.

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1891: Clarence M. Kemp of Baltimore patents the Climax, the first commercial solar water heater (U.S. Patent 451,384, 28 April 1891). Black tanks enclosed in a glass-covered, insulated box heated water using solar energy. The system sold especially well in Southern California; by the late 1890s, roughly one-third of homes in Pasadena used solar water heating.

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1897–1898: Edwin Ruud leaves the Fuel Gas company, founds Ruud Manufacturing, and patents an improved automatic instantaneous (coil-type) water heater (U.S. Patent 610,281, 6 September 1898). This design used a copper coil inside a cast-iron shell with thermostatic gas control. Ruud popularized both storage and instantaneous automatic heaters and remained a major manufacturer for decades (later under Rheem).

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1909–1910: William J. Bailey patents the Day and Night solar water heater. The critical innovation was separating the outdoor flat-plate collector from an insulated indoor storage tank, allowing hot water day and night via thermosyphon circulation. Thousands were installed in California; rights were later transferred to Florida, where solar water heating became widespread until cheap natural gas displaced it.

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1900–1945: Electrification, Mass Production Foundations, and War

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1924–1927: Dr. Theodor Stiebel founded ELTRON in Berlin and developed the coil immersion heater (1924). In 1927, the company produced its first small instantaneous electric water heater — an early commercial electric tankless design. Stiebel Eltron would become a major force in electric water heating.

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1930–1931: Rheem enters the automatic gas storage water heater market. By 1941, the company is the largest U.S. manufacturer of automatic water heaters.

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1936: A.O. Smith patents a process for glass-lining steel tanks (adapted from its brewery-tank technology developed during the Depression). Glass lining dramatically improves corrosion resistance and makes reliable, affordable storage tanks practical for average households.

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1939: A.O. Smith begins mass production of residential glass-lined water heaters. Production is interrupted by World War II, during which the company manufactures bombs, aircraft components, and military water heaters.

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1946: State Water Heaters is founded in Nashville by Herbert Lindahl Sr. The company later pioneers foam insulation between the tank and jacket (late 1970s) and is acquired by A.O. Smith in 2001.

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1948: A.O. Smith acquires the Burkay Company, entering the commercial instantaneous and coil-type market. The first glass-lined commercial water heater (Burkay B-65) appeared in the early 1950s.

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Post-War Expansion (1945–1980s)

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Late 1940s–1950s: Post-war housing boom and expanding gas and electric utility networks drive rapid adoption of automatic storage water heaters. Glass lining becomes the industry standard. Monthly production at major plants reaches tens of thousands of units.

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1950s–1960: Continued refinement of thermostats, immersion elements, anode rods, and safety controls. Electric storage heaters become practical in more regions as electrical infrastructure improves.

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1970s: Energy Crises: Rising energy costs spur interest in efficiency. Foam insulation reduces standby heat loss. Early modern tankless systems gain attention in Europe and Japan; U.S. interest begins to grow.

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In the late 1970s, State Water Heaters pioneered the use of polyurethane foam insulation between the tank and outer jacket, a major improvement over earlier fiberglass methods.

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Efficiency Era & Modern Systems (1987–Present)

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1987: National Appliance Energy Conservation Act (NAECA) establishes the first federal minimum efficiency standards for residential water heaters in the United States (effective approximately 1990). Subsequent DOE rulemakings progressively raise requirements.

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1990s–2000s: Modern gas tankless water heaters, refined by Japanese manufacturers (notably Rinnai and others), enter the U.S. market in greater numbers. Condensing technology, digital controls, and better reliability drive adoption. Energy efficiency and unlimited hot water become primary selling points.

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In 2009, ENERGY STAR began certifying heat-pump water heaters. These units, which move heat rather than generate it directly, achieve coefficients of performance typically between 2 and 4.

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2010s–2020s

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• Continued tightening of DOE efficiency standards (including the 2015 update that effectively pushed larger electric storage units toward heat-pump technology).

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• Growth of hybrid heat-pump water heaters with electric resistance backup.

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• Condensing tankless systems are becoming more common.

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• Integration of recirculation, smart controls, and improved scale resistance for hard-water regions.

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• Ongoing research into further efficiency gains, materials, and grid-interactive systems.

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Notes on Sources & Accuracy

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Dates and attributions on this timeline are drawn from patent records (USPTO and historical British patents), manufacturer histories, contemporary engineering literature, and museum collections. Common online discrepancies (especially around Ruud’s 1889 design versus 1890 patent) have been resolved in favor of primary documentation.

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This timeline is updated as new verified research becomes available.