Electric Water Heater: Safety Features to Check

Electric water heater safety comes down to four parts: earth-leakage protection, a relief valve, a thermostat you can set, and a clean installation. Check all four before you pay. Water and mains power sit very close together in a bathroom, so a small fault can matter a lot.

This guide is general information, not medical advice and not a substitute for a licensed electrician. It lists what to look for in a shop and what to ask the installer.

1. Ask about earth-leakage protection

An earth-leakage device is the most important electrical safety part. It watches the current going out on one wire and coming back on the other. If some current leaks away, for example through a person or a wet fault, the two no longer match. The device then cuts the power very fast.

Common devices of this kind are often called RCDs or ELCBs. A rating of about 30 mA is the usual choice for protecting people from shock in many countries. Some water heaters come with the device built into the power cord plug. Others rely on a breaker in your home. Ask which one you are getting, and ask to see it.

Look for a test button on the device. Pressing it makes a small, pretend leak. The device should switch off at once. If it does not, it must be replaced. Press the button on a regular schedule, such as once a month, and note the date.

Know the limit too. This device lowers the harm from a shock. It cannot help if someone touches both live wires at once.

Sources: Wikipedia, "Residual-current device" (https://en.wikipedia.org/wiki/Residual-current_device), on how the device compares current, the 30 mA protection level, the test button and its limits.

2. Confirm the earth wire and the cable

A metal tank needs a working earth connection. The earth wire gives stray current a safe path. Ask the installer to confirm that your bathroom socket or wall box has an earth terminal, and that it is connected. Do not accept a heater wired to a two-pin socket with the earth wire left loose.

Check the power cable size too. A heater draws a lot of power while it heats. Small point-of-use units commonly use an element of about 1 to 1.5 kW, and larger tank units use more. Read the power figure on the label and ask the installer if your wiring can carry it. A thin cable or a worn socket can overheat.

Keep the heater and its controls out of direct splashes. Ask the installer where the plug or switch will sit. It should be out of reach of the shower spray.

Sources: Wikipedia, "Water heating" (https://en.wikipedia.org/wiki/Water_heating), on typical element sizes of small electric heaters.

3. Look for a relief valve on a tank heater

A storage heater keeps a tank of hot water under pressure. Household tanks are typically between 75 and 400 litres. If the water gets too hot, or the pressure builds up, the tank needs a way to let it go. This is the job of a temperature and pressure relief valve, usually mounted on top.

Ask where the valve is and where it drains. The drain pipe should lead to a safe spot, away from people. Never block the valve or cap it. If a valve drips often, call a repair person instead of plugging it.

Open-vented and pressure models differ, so ask the seller which kind you are buying and what safety part it uses. A good seller can show you the part, not just describe it.

Sources: Wikipedia, "Water heating" (https://en.wikipedia.org/wiki/Water_heating), on tank sizes and the temperature and pressure relief valve.

4. Use a thermostat and keep the heat sensible

A thermostat keeps the water at the set temperature. Choose a model with a dial or marked settings you can read. Also ask about a second cut-off that switches the element off if the thermostat fails.

Hot water can burn skin fast. Skin can burn in under 5 seconds at 60 degrees Celsius. At 53 degrees it takes about a minute to cause a second-degree burn. This matters most for children and older family members. Many people set the tank near 55 degrees as a balance between scald risk and keeping the water clean. Mix the water with cold at the tap before you step in.

The thermostat only reads the water at its own height. Water lower in the tank can be cooler. So test the water at the tap with your hand briefly, or use a thermometer, rather than trusting the dial alone.

Sources: Wikipedia, "Water heating" (https://en.wikipedia.org/wiki/Water_heating), on scald times, the 55 degree setting and thermostat placement.

5. Get a proper installation

A safe heater can still be made unsafe by poor fitting. Ask a qualified installer to do the job, and ask what is included in the price: cable, breaker, valve, hoses and wall bracket. Ask for the warranty card and keep it with your receipt.

Make sure the wall can hold a full tank. Water is heavy, so a 50 litre tank weighs about 50 kilograms before the heater itself is counted. Use the bracket supplied and fix it into solid wall, not a thin panel.

Ask the installer to explain how to switch the heater off at the wall, and where the breaker is. Learn this before something goes wrong.

Quick checklist

• Earth-leakage device with a test button, tested monthly.
• Earth wire connected, and a cable and socket that suit the power figure on the label.
• Relief valve with a safe drain on a tank heater.
• Thermostat with readable settings and a second cut-off.
• Qualified installer, solid wall fixing, and a warranty card.

Print the list and take it to the shop. A seller who answers each point clearly is a good sign.

Sources

• Wikipedia, "Residual-current device": https://en.wikipedia.org/wiki/Residual-current_device
• Wikipedia, "Water heating": https://en.wikipedia.org/wiki/Water_heating