The core idea: one heater, two kinds of hot water
Behind a wall or out on the balcony sits one water heater, kyūtōki (給湯器), literally supply-hot-water device. It sends hot water two ways. Kyūtō (給湯) is water from the taps and the shower, where the panel simply sets the temperature. Furo (ふろ) is the tub, which the heater can fill, reheat and keep warm through a fitting in the tub wall. Every button on the panel belongs to one side or the other.
Over both sits unten (運転), operation, the same word as driving a car: the master switch, marked iri and kiri for on and off. When it is off the heater does not fire, and the hot taps run cold. That one fact solves most first-night problems. The etiquette of the bath itself, washing before you get in and sharing the water, is covered in a separate guide.
| Button | Reading | Side | What it does |
|---|---|---|---|
| 運転 入/切 | unten iri/kiri | Both | Turns the heater on or off |
| 給湯温度 | kyūtō ondo | Taps | Sets tap and shower temperature |
| 優先 | yūsen | Taps | Gives this panel control of tap temperature |
| ふろ自動 | furo jidō | Tub | Fills, announces, keeps warm |
| ふろ温度 | furo ondo | Tub | Sets the bath temperature |
| 湯量 | yuryō | Tub | Sets how full the tub gets |
| 追いだき | oidaki | Tub | Reheats the water already in the tub |
| たし湯 | tashiyu | Tub | Adds more hot water |
| 保温 | hoon | Tub | Keeps the bath warm for set hours |
The bathroom panel, button by button
The bathroom panel, yokushitsu rimokon (浴室リモコン), is waterproof and sits beside the tub or shower. A typical layout puts unten and the display at the top, the tap-temperature arrows on one side and the bath buttons on the other, with furo jidō the largest. The display shows two numbers: the tap temperature and the bath temperature. Some panels hide less-used keys, such as yuryō and hoon, under a flap.
Makers write the same button differently. Furo jidō may be jidō or ofuro; oidaki appears as 追いだき, おいだき or 追焚; tashiyu may be たし湯 or 足し湯. The job is the same, so read the kanji you know and the position. A host showing a new flatmate the panel might put it like this.
| Japanese | Romaji | Meaning |
|---|---|---|
| まず運転を入れてね。 | Mazu unten o irete ne. | First, switch it on. |
| シャワーの温度はここで変えられるよ。 | Shawā no ondo wa koko de kaerareru yo. | You can change the shower temperature here. |
| お風呂はふろ自動を押すだけ。 | Ofuro wa furo jidō o osu dake. | For the bath, you just press furo jidō. |
| ぬるかったら追いだきして。 | Nurukattara oidaki shite. | If it's lukewarm, reheat it. |
| お湯が少なかったら、たし湯ね。 | Oyu ga sukunakattara, tashiyu ne. | If there's not enough water, top it up. |
Furo jidō from an empty tub to keep-warm
Furo jidō is a sequence, and the panel narrates it. Put the plug, sen (栓), in the tub and close the lid. Press furo jidō; its lamp flashes while the tub fills through the wall fitting. Filling a tub is oyuhari (お湯はり), from yu o haru, where haru literally means to stretch or spread. Near the end the panel beeps and warns that the bath is almost ready. When the set level and temperature are reached, a melody plays and the voice says ofuro ga wakimashita.
Then comes hoon. For the number of hours set, often four by default, the heater watches the tub and reheats it if it cools; full-auto models also top up the level. When the hours run out, the lamp goes off by itself. Until then the machine is still in charge of the tub, which matters when you drain it.
What the recorded voice is telling you
The announcements are short, polite masu forms, with the panel speaking as a helpful machine, so they are easy to learn by ear. Exact wording varies by maker; these are typical. If yours plays only a melody, the voice may be switched off in the settings.
| Japanese | Romaji | Meaning |
|---|---|---|
| お湯はりをします。 | Oyuhari o shimasu. | I'll fill the bath now. |
| おふろの栓を確かめてください。 | Ofuro no sen o tashikamete kudasai. | Please check the bath plug. |
| まもなくおふろが沸きます。 | Mamonaku ofuro ga wakimasu. | The bath will be ready shortly. |
| おふろが沸きました。 | Ofuro ga wakimashita. | The bath is ready. |
| 4時間保温します。 | Yo-jikan hoon shimasu. | I'll keep it warm for four hours. |
| おいだきをします。 | Oidaki o shimasu. | Reheating the bath. |
| 20リットルのお湯をたします。 | Nijū rittoru no oyu o tashimasu. | Adding 20 litres of hot water. |
| あついお湯が出ます。 | Atsui oyu ga demasu. | Very hot water will come out. |
| おふろで呼んでいます。 | Ofuro de yonde imasu. | Someone is calling from the bath. |
Confusable buttons: oidaki, tashiyu and the two temperatures
Oidaki (追いだき) is literally chase-heating: the heater draws the tub water out through the wall fitting, heats it and sends it back. The level stays the same and only the temperature rises. It needs water above the fitting, and it reheats water someone may already have bathed in, which is normal in a Japanese family bath.
Tashiyu (たし湯), literally added hot water, pours in new water at the bath temperature, about 20 litres a press on many models. The level rises and the temperature barely changes. Its partner tashimizu (たし水), added water, cools a bath that is too hot. So: too cold, oidaki; too little, tashiyu; too hot, tashimizu.
The two temperatures are another pair. Kyūtō ondo is what comes out of the taps and shower; furo ondo is what the tub is filled and kept at. Turning up the shower does nothing to the bath, and the reverse. In the evening, family members call to each other between rooms.
| Japanese | Romaji | Meaning |
|---|---|---|
| お風呂ちょっとぬるいから、追いだきして。 | Ofuro chotto nurui kara, oidaki shite. | The bath's a bit lukewarm, reheat it, please. |
| お湯が減ってるから、たし湯しようか。 | Oyu ga hetteru kara, tashiyu shiyō ka. | The water's gone down, shall we add some? |
| 熱すぎるなら、水をたせばいいよ。 | Atsusugiru nara, mizu o taseba ii yo. | If it's too hot, just add cold water. |
Kitchen panel versus bathroom panel
Most homes with a bath-filling heater have two panels. The kitchen panel, daidokoro rimokon (台所リモコン), is simpler: unten, tap temperature and usually furo jidō, so you can start the bath while cooking. The bathroom panel adds tub controls such as oidaki and tashiyu. Both play the same announcements, so the kitchen knows when the bath is ready.
Two buttons exist because of the pair. Yūsen (優先), priority, decides which panel controls the tap temperature; the bathroom panel usually takes it while someone showers, so nobody in the kitchen can change it. Tsūwa (通話), talk, or on simpler panels yobidashi (呼び出し), call, lets someone in the bath speak to or buzz the kitchen.
| Japanese | Romaji | Meaning |
|---|---|---|
| 台所からお風呂沸かしておくね。 | Daidokoro kara ofuro wakashite oku ne. | I'll start the bath from the kitchen. |
| 今、お風呂のリモコンが優先になってるよ。 | Ima, ofuro no rimokon ga yūsen ni natteru yo. | Right now the bathroom panel has priority. |
| シャンプーがないから、持ってきて。 | Shanpū ga nai kara, motte kite. | There's no shampoo, could you bring some? |
| お風呂のリモコンで呼んだ？ | Ofuro no rimokon de yonda? | Did you call from the bath panel? |
Beyond the basics: hoon hours, full-auto models and error numbers
Hoon hours are adjustable with a hoon or hoon jikan key; choices typically run from zero to several hours, and four is a common factory setting. Zero means the panel fills the tub and then leaves it alone.
Heaters come in grades. An ōto (オート) model fills the tub and keeps the temperature. A furu ōto (フルオート), full-auto, model also tops up the level during keep-warm and, on many models, rinses the pipe to the tub when you pull the plug after bathing. Homes with an electric heat-pump system, often called Eco Cute, heat a tank of water at night; their panels add a remaining hot water gauge, zantōryō (残湯量), and can run out, yugire (湯切れ), after heavy use.
When something goes wrong, the display shows a number instead of a temperature: the maker's error code. Note it down, photograph the sticker on the heater unit, and give both to the management company or gas company when you call.
| Japanese | Romaji | Meaning |
|---|---|---|
| リモコンに数字が点滅しています。 | Rimokon ni sūji ga tenmetsu shite imasu. | A number is flashing on the panel. |
| お湯が出なくなりました。 | Oyu ga denaku narimashita. | The hot water has stopped coming out. |
| お風呂のお湯はりができません。 | Ofuro no oyuhari ga dekimasen. | The bath won't fill. |
| 管理会社に連絡してみます。 | Kanri gaisha ni renraku shite mimasu. | I'll try contacting the management company. |
Common mistakes with a Japanese bath panel
Leaving unten off and wondering why the shower is cold. The cause is expecting hot water to be always available, as with a hot-water tank. A gas heater only fires when the panel is on; press unten.
Pressing furo jidō without the plug in. The cause is a tub that looks ready. The water drains as it fills, which is why many panels say ofuro no sen o tashikamete kudasai. Plug first, then press.
Pressing oidaki on an almost empty tub. The cause is reading oidaki as heat the bath. It only circulates water that is already there and needs water above the wall fitting; use furo jidō or tashiyu instead.
Pulling the plug while keep-warm is still running. The cause is not noticing the furo jidō lamp. On full-auto models the heater sees the level drop and adds water again. Press furo jidō to switch it off, then drain.
Topping up from the tap during automatic filling. The cause is impatience. The heater measures the level itself, so extra water can make the tub overflow.