Top 13 Important Parts and Terms to Know to Better Understand Your Water Heater

Dunedin’s cold climate and unpredictable weather mean that around-the-clock access to hot water is more important than it is compared to other areas elsewhere in New Zealand. Few other cities in the country get below-freezing temperatures in winter and ground frost in the spring, making a functioning water heater a priority in any Dunedin property. A malfunctioning water heater during these times can cause serious discomfort and possibly even result in costly repairs if you don’t attend to it right away.

Thankfully, knowing the key parts and parlance of water heaters can make maintaining, troubleshooting, and choosing the right upgrades that much easier. Learn what the terms below mean, and you’ll be on your way to having a reliable water heater that works when you need it to. Then, when it’s time to upgrade or fix your water heater, don’t forget to call plumbers Dunedin property owners depend on—like us here at Mains Plumbers.

1. Thermostat

Thermostats are automatic controls that keep water inside the heater at a set temperature. Most modern units will give you a way to control the temperature, like a manual knob or a digital remote; the usual range is from 40°C to about 60°C. A faulty thermostat can lead to inconsistent water temperatures, which can be frustrating and even dangerous at times. As ambient temperatures change, periodically check and adjust your heater’s thermostat so you get a good balance between comfort and energy efficiency.

2. Heating Element

Most commercially available electric water heaters rely on at least one heating element to warm the water. These elements work similarly to the heating coils in an electric kettle, except at a larger scale. As with electric kettles, mineral buildup from hard water can reduce your water heater’s efficiency, making it important to periodically check, maintain, and replace the heating element as needed.

2. Heating Element

Most commercially available electric water heaters rely on at least one heating element to warm the water. These elements work similarly to the heating coils in an electric kettle, except at a larger scale. As with electric kettles, mineral buildup from hard water can reduce your water heater’s efficiency, making it important to periodically check, maintain, and replace the heating element as needed.

3. Anode Rod

Mineral buildup and corrosion are primary concerns for home water heaters. For that reason, most home water heating systems have an anode rod that attracts minerals and sediment, preventing damage to the tank’s interior. Anodes can last for years, but they are all “sacrificial” and will eventually cease to function. When that happens, it’s only a matter of time before the heater is choked with minerals and starts to clog or leak. 

It’s generally good practice to replace the anode rod every 3 to 5 years, perhaps sooner if your water has higher mineral content. Before you install a new anode rod, be sure to check the recommended replacement frequency and consider ordering a replacement ahead of time.

4. Sediment Buildup

Even with an anode rod, some minerals and debris will eventually accumulate at the bottom of the water heater tank. While mostly harmless, this sediment buildup can reduce efficiency. If you leave sediment to build up, your water heater can overheat, start making loud noises, or even fail completely. Flushing the tank every 6 months (or more frequently if you have hard water) can prevent these issues and improve your heater’s performance.

5. Pressure Relief Valve

This safety device is designed to release excess pressure from the water heater tank, much like the one on a typical pressure cooker. If the pressure inside the tank builds up too much, this valve will automatically open to prevent explosions and warping in your plumbing. When maintaining your heater, always check that the pressure relief valve is functioning properly. If you suspect a malfunction, contact a qualified plumber immediately.

6. Cold Water Inlet Valve and Dip Tube

The cold water inlet valve controls the flow of cold water into the heater’s tank. This is usually connected to a dip tube that directs incoming cold water to the bottom of the tank, allowing for more efficient heating. If either of these components is broken or deteriorated, your heater may become less efficient, causing lukewarm water to come out of your taps instead of hot water. Check these components if your water heater has trouble maintaining a target temperature.

7. Tank Insulation

Proper insulation helps keep your heated water hotter for longer, reducing the need to turn on electric heating elements or fire up some gas. However, insulation can increase the cost of a water heater, which means that many home heaters lack any insulation, resulting in higher energy usage in the colder months. Models that lack insulation may require additional insulating blankets for better performance.

8. Pilot Light and Thermocouple (for Gas Water Heaters)

Some gas-fired water heaters use a small flame, known as a pilot light, to ignite the burner that heats the water. If the pilot light goes out, a safety mechanism called the thermocouple may keep the heater from releasing gas into the burner, which prevents the heater from running. Provided the rest of the heater is functioning, checking and relighting the pilot light should restore a steady supply of hot water. 

9. Expansion Tank

Some plumbing systems require extra space to accommodate the thermal expansion of water as it heats up. This prevents pressure from building up and damaging your plumbing. If your water heating system lacks an expansion tank, you may start experiencing pressure-related issues, especially as your heater ages.

10. Recirculation Pump



Some modern water heating systems use a secondary pump to keep hot water readily available, which means you won’t have to keep your taps running before you get hot water. While these pumps save water, they also increase the complexity and maintenance needs of your water heating system. They may need to be flushed occasionally to prevent clogging and excess pressure buildup.

11. Energy Factor Rating

The Energy Factor or EF rating measures the relative efficiency of a water heater. This is done by comparing the amount of hot water produced to the amount of energy needed. A higher EF rating indicates better energy efficiency, which can be important when you’re choosing between two similar heaters.

12. Gas Burner (for Gas Water Heaters)

In gas-fired heaters, the burner is what heats the water, directly analogous to the burner on a typical gas stove. Located beneath the tank, it automatically ignites when the thermostat signals the need for heat. As with stove burners, water heater burners can corrode or become clogged with debris when not maintained, so periodic maintenance is necessary to maintain efficiency.

13. Flue Pipe (for Gas Water Heaters)

In gas water heaters, the flue pipe serves as an exhaust system, venting harmful gases like carbon monoxide safely outside the home. A damaged or blocked flue pipe can lead to dangerous gas buildup. Schedule regular inspections of the flue pipe to help ensure safety.

Keep Your Water Heater in Peak Condition

As with many other things, knowledge is power. Once you understand your water heater’s components, you’ll get a better appreciation of how it works and what must be done to keep it in good running order.

For expert water heater maintenance and installation services in Dunedin, you can trust the team at Mains Plumber. Our experienced professionals are also fully qualified to perform emergency plumbing services in case you need your heater fixed immediately. If you have a gas-powered water heater, we also have licensed gas fitters who can diagnose and fix any issues. Contact us today to keep your hot water running year-round.