Water heaters are a familiar appliance in most households, especially during colder months. However, improper use can turn this convenient device into a serious safety hazard.

In December 2023, a water heater unexpectedly exploded in a home in Ha Long City, Vietnam, despite no one using it at the time. The blast severely damaged the bathroom ceiling. Fortunately, no injuries were reported. According to the homeowner, the water heater was usually left switched on continuously and only turned off during showering.

This incident alarmed many people because it stemmed from a habit widely considered harmless: leaving the water heater on all day and night for convenience. Experts warn that this practice is one of the leading causes of equipment failure, excessive electricity consumption, and increased risk of fire or explosion.

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Why You Should Not Leave a Water Heater On Continuously

In principle, when powered on, an electric water heater heats water to a preset temperature, then automatically shuts off via a thermostat. Once the water cools down, the thermostat reconnects the circuit and reheats the water. This creates a constant cycle of heating – stopping – reheating, even when no hot water is being used.

According to electrical engineers, keeping the heater in this mode forces it to operate nearly 24/7. Over time, this causes excessive strain on internal components, shortens the appliance’s lifespan, and significantly increases the risk of electrical faults or explosions.

Key components such as the heating element, temperature sensor, insulation, and wiring deteriorate much faster under continuous operation. If the thermostat loses accuracy or pressure builds up due to overheating, the unit may leak electricity, crack, or even explode.

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Increased Electricity Bills and Energy Waste

Beyond safety concerns, leaving a water heater on continuously leads to substantial electricity waste. Tests show that a 2,431-watt water heater running nonstop for two days can consume nearly 14 kWh of electricity. Over a month, this can translate into electricity costs exceeding the equivalent of running an air conditioner for many hours daily.

Vietnam Electricity (EVN) identifies water heaters as the second-largest electricity-consuming appliance in households, after air conditioners. Similarly, the U.S. Department of Energy estimates that water heating accounts for about 18% of total household energy use, more than refrigerators or washing machines.

A 2024 study published in Energy Informatics found that over 50% of users keep their water heaters in “continuous heating” mode, leading to significant energy waste and reduced appliance lifespan. Researchers noted that simply adjusting heating schedules and lowering temperature settings could save 20–30% of monthly electricity consumptionwithout affecting daily comfort.

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Recommended Usage for Safety and Efficiency

Experts generally advise that households should operate water heaters for only 1–3 hours per day, depending on family size and season.

• Turn the heater on 15–30 minutes before showering, then switch it off immediately afterward.

• In colder months, 30–60 minutes of heating is usually sufficient.

• In warmer seasons, 15–20 minutes is often enough.

• Using a timer to automatically control heating during peak usage times is strongly recommended.

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Warning Signs You Should Never Ignore

According to electrical safety specialists, most water heater accidents do not happen suddenly. They are often preceded by warning signs, including:

• Unusual noises or persistent humming, indicating scale buildup or unstable heating elements

• Weak hot water output or longer heating times, suggesting thermostat or sensor malfunction

• Water leaks around the tank or base, especially after long periods without maintenance

• A burning smell near the power socket or wiring, signaling a potential electrical short circuit

If any of these signs appear, the power supply should be disconnected immediately, and a qualified technician should be contacted. Never attempt to repair or dismantle the unit yourself.

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The Importance of Regular Maintenance

Routine maintenance is essential for safety. Experts recommend servicing water heaters at least once a year, or every six months in areas with hard water. Maintenance includes cleaning the heating element, checking safety valves, inspecting wiring, and ensuring insulation integrity.

Statistics show that water heaters used for more than five years without maintenance are significantly more likely to leak electricity or explode. Some manufacturers advise replacing units after 7–10 years, particularly if rust or metallic-smelling water is detected.

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Conclusion

The water heater explosion in Ha Long is a stark reminder that danger can arise from everyday habits. Leaving the heater on “for convenience” not only increases electricity bills but also puts constant stress on the device, creating serious safety risks.

Experts emphasize that small habit changes—turning the heater off after use, scheduling heating times, and performing regular maintenance—can greatly reduce risks and protect household safety. Sometimes, what seems like a convenient shortcut can become the very cause of an avoidable disaster.