Why Did the Warm Water in a Japanese Toilet Seat Suddenly Turn Cold?

Press a button beside a Japanese toilet seat, and warm water comes out, but where is that water heated? And why did the very system that keeps the water warm once make it cold? Ahead of World Toilet Day (November 19, a United Nations observance), Sayo and Hau follow the warm-water bidet seat's long battle with temperature, from a medical seat imported from America in 1964 to an idea borrowed from traffic signals. Chapters 00:00 Where is the warm water heated, and why did it once turn cold? 00:45 Chapter 1: A Medical Seat from America 02:36 A weak point: the water temperature was unstable 03:57 Chapter 2: Where 300 People Sat, and Three Temperatures 05:59 Chapter 3: The Highlight — Unsteady with the Plate, Fatigue with the IC 07:14 Electronics near water? An idea from traffic signals 07:50 June 1980: TOTO's "Washlet" goes on sale 09:22 Chapter 4: Where Is the Water Heated? 10:35 How widespread did seats like this become in Japan? 11:07 Field notes from our supervising electrician 11:52 Closing: Two Answers About this video Supervised by a licensed electrician (the channel owner). Field notes are from our supervising electrician's own experience. This video is a history of household tools, not advice on electrical work or safety. Scene images are AI-generated illustrations, not photographs of real products, places or people. Diagrams are drawn by our own program. Narration is an AI voice (Kokoro-82M, Apache-2.0). Sayo/SAYO and Amehare Hau are used as unofficial fan works. This channel is an independent production, not an official one. Where sources disagree, we either leave the point out or say which source we follow. Main sources "The Introduction of Bidet Toilet Seats," High-Tech Toilets, Kids Web Japan (Web Japan, Ministry of Foreign Affairs of Japan) https://web-japan.org/kidsweb/hitech/... 100 Japanese Postwar Innovations: [warm-water bidet seat] — Background (in Japanese) https://koueki.jiii.or.jp/innovation1... Toilet Timeline, Japan Sanitary Equipment Industry Association (in Japanese) https://www.sanitary-net.com/history.... Mechanical Engineering Heritage No. 55 (designated 2012): [warm-water bidet seat], The Japan Society of Mechanical Engineers (in Japanese) https://www.jsme.or.jp/kikaiisan/heri... News release on the 40th anniversary of the [warm-water bidet seat] launch (June 23, 2020), PDF, TOTO LTD. (in Japanese) https://www.toto.com/jp/press/pdf/202... "The Birth of the Shower Toilet" (History of Manufacturing), LIXIL Corporation (in Japanese) https://www.lixil.co.jp/square/histor... 100 Japanese Postwar Innovations: [warm-water bidet seat] — Overview of Technical Development (in Japanese) https://koueki.jiii.or.jp/innovation1... TOTO History, Challenge 5: [warm-water bidet seat], TOTO LTD. (in Japanese) https://jp.toto.com/pages/history/cha... History of the [warm-water bidet seat], a page by a TOTO subsidiary (in Japanese) https://twt.jp.toto.com/product/histo... Toilet Q&A: "Warm-water bidet seats come in instantaneous and storage types. What are they?", Japan Sanitary Equipment Industry Association (in Japanese) https://www.sanitary-net.com/faq/answ... Consumer Confidence Survey, long-term time series: diffusion rates of major consumer durables (households of two or more people), Cabinet Office (via e-Stat) (in Japanese) https://www.e-stat.go.jp/stat-search/... Consumer Confidence Survey: results of the March 2026 survey (report), Cabinet Office (in Japanese) https://www.esri.cao.go.jp/jp/stat/sh... Other sources are shown on the source cards in the video (top right of the screen). Credits Voice: Kokoro-82M (Apache-2.0) Character art: Oyodo Hisaaki (大淀久明 様) Characters: Sayo/SAYO (小夜), Amehare Hau (雨晴はう) — unofficial fan work (非公式の二次創作) BGM: "Hirusagari Kibun" (昼下がり気分) by KK (DOVA-SYNDROME / OpenTracks) #JapaneseToilet #BidetSeat #ShowaJapan