By the HalfKey team
No hot water in a Tokyo apartment: what to check first
Whether the hob still lights tells you where to look. A blinking gas meter needs a careful reset, an ignition error usually points back to the gas supply, and an electric tank may simply be empty for the day.
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Turn on one burner of the gas hob. If it lights, gas is reaching the apartment and the problem is in the water heater. If nothing lights, go to the gas meter. If you smell gas at any point, stop checking and use the leak steps near the end of this guide instead.
Water-heater makers start with the same question. Noritz's guidance for its ignition error tells you to check first whether other gas appliances, such as the hob, will light. If they won't, the heater probably isn't getting gas and should work again once the supply is restored. If they do, the heater itself likely needs a repair. Tokyo Gas Network's no-gas checklist covers the same check in English.
If your kitchen has an induction hob, you can't use this test. Start with the water heater's control panel, then check the gas meter if the apartment has one.
| What you notice | Likely cause | What to do first |
|---|---|---|
| The hob lights, but the shower stays cold and the panel shows a number | A water-heater fault | Write down the code and report it |
| Neither the hob nor the hot water works | The gas meter has shut off, or its tap is closed | Check the meter's red light |
| The control panel is completely dark | No power reaching the heater | Press the on button, then check the breakers |
| The panel shows a nearly empty tank gauge | An electric hot-water tank has run out | Use the reheat button, or wait |
| On a freezing morning, the hot tap gives no water at all | A frozen pipe | Switch the heater off and wait for it to thaw |
Read the water heater's control panel
Look for the 給湯リモコン (kyūtō rimokon — water-heater control panel) on a kitchen or bathroom wall. Not every heater has one. If the display is dark, press the 運転 (unten — on) button. If it stays dark, check the apartment's breaker panel, the box of switches that controls the power. A gas water heater with a control panel still needs electricity: Tokyo Gas lists these heaters among the gas appliances you can't use during a power cut.
A blinking number on the panel is an error code. Write it down and photograph it. On Noritz heaters, 111 means the burner failed to light, and Rinnai's help page for the same code opens with the same hob question.
In an apartment building, Rinnai notes that the heater itself may be on the balcony or near the gas meter. The label on the heater shows the maker and model number, which anyone arranging a repair will ask for.
If the gas meter's red light is blinking
An apartment's gas meter is usually in a meter box beside the front door or along the shared hallway. Tokyo Gas Network's meter page shows how the common box latches open. It also warns that the key to a locked box is often kept by the building manager.
A blinking red light means the meter's safety device has stopped the gas. According to Tokyo Gas Network's meter guide, this happens when the meter detects an unusually large flow, a drop in gas pressure, strong earthquake shaking (about 5-strong or more on Japan's seismic intensity scale), or gas flowing steadily for a very long time. A bicycle or bag knocking against the meter can also set it off.
If there is no gas smell, you can reset it yourself:
- Turn off every gas appliance, including the water heater. Switch its control panel off too.
- If the reset button has a cap, take it off. Leave the meter's own gas tap open.
- Press the reset button firmly all the way in, then release it slowly. The red light comes on and then starts blinking again.
- Wait without using any gas. On the common meter with a capped button, that's three minutes. Some newer meters need only one or two, so follow the label on yours.
- When the light stops blinking, the gas is back. Put the cap back, turn the water heater on and run the hot tap.
The meter uses those minutes to check for a leak, and the gas stays off until it finishes. If the light is still blinking afterwards, check again for anything left on, such as a bath filling, and repeat from the first step.
After a large earthquake, Tokyo Gas Network may also stop the supply to a whole area for safety. A reset won't bring the gas back then. Its Japanese reset page links to a restoration map, and in an affected area you wait for the supply to restart.
While you're at the meter, look at its gas tap. Tokyo Gas Network's checklist says it should point vertically; if it's horizontal, turn it upright.
These are Tokyo Gas Network's instructions. If the meter or bill shows another gas company, follow that company's label. LP (bottled) gas meters also shut off automatically, but the reset button can be in a different place.
After the reset, check the water temperature on the control panel. Some heaters return to their default settings after losing power.
An electric hot-water tank that has run out
Some buildings use an electric storage tank, which heats the day's hot water in advance. Hitachi's guide for its tanks says the control panel shows how much hot water is left. When the tank is empty, the shower runs cold until it heats more.
Hitachi's advice when you're running low is to press タンク沸き増し (tanku wakimashi — heat more water). It estimates that one hour of heating makes about 120 litres of 40°C water in winter, or 240 litres in summer, and that a shower uses about 10 litres a minute.
So an hour of reheating on a winter evening gives roughly 120 ÷ 10 = 12 minutes of showering. Filling a bath, which Hitachi puts at about 180 litres, needs more than an hour's winter reheating. If you often run short, Hitachi suggests a setting that heats more water each day. In a rental, ask the rental company before changing it, since it changes how much electricity the tank uses.
Cold mornings: a frozen pipe
On a freezing morning, if the hot tap gives no water at all, a pipe to the water heater may have frozen. Tokyo Gas's freezing advice is to switch off the control panel, leave the heater plugged in and wait for the temperature to rise. It warns that pouring hot water over the pipes or using a hair dryer can damage them. When water flows again, check the heater and its pipes for leaks before using it normally.
Rinnai counts November to February as its freezing season, including in warmer regions. A snowman symbol or 凍結予防 (tōketsu yobō — freeze prevention) on its panels means the heater is protecting itself. That isn't a fault. Rinnai also warns that if you ask a repairer to visit for a frozen pipe, you pay for the visit even when nothing is damaged, so waiting for the thaw is usually the right first step.
Stop and report instead
Leave the troubleshooting and get help when:
- You smell gas. Don't reset the meter. Don't light a flame or touch light or fan switches, since they can spark. Open the windows, close the gas taps and move away. For buildings supplied by Tokyo Gas Network, call its 24-hour gas-leak line on 0570-002299, or 03-6735-8899 if that number won't connect. The apartment emergencies guide covers what to do when there's fire or other danger.
- The meter won't reset, or keeps stopping the gas. Tokyo Gas Network asks you to contact it in both cases.
- The hob works, but the error code returns. The heater itself likely needs repair.
- Water is leaking from the heater. Rinnai's advice is to close the valve that shuts off water to the heater, then report it.
In a rented apartment, report a water-heater fault to the rental company rather than calling the maker yourself. Rinnai asks tenants to arrange repairs through their management company. If the gas has been stopped over an unpaid bill, the utility cut-off guide explains who needs to act.
Send one message with everything the repair company will ask about:
No hot water at [address and room] since [time]. The gas hob [does / doesn't] light. The water heater panel shows [error code, or "nothing"]. The gas meter light is [blinking / off], and I [did / didn't] try a reset at [time]. Photos of the panel and the label on the heater are attached.