How Do Hot Water Systems Work?

Hot water systems are integral to every home, providing comfort and convenience for daily activities such as bathing, cooking, and cleaning. But how exactly do these systems work? This article provides an overview of how various types of hot water systems function, their components, and the importance of regular maintenance. When it comes to professional services for your hot water system, look no further than Superior Plumbing Drainage & Gas, your trusted local expert plumber in Perth. 

Types of hot water systems 

Hot water systems come in various forms. Here are the three primary types: 

  1. Storage tank water heaters: This is the traditional type of water heater and is most commonly used in residential settings. The system consists of an insulated tank that heats and stores water until it’s needed. 
  2. Tankless water heaters: Also known as demand-type or instantaneous water heaters, these devices heat water directly without storing it, providing hot water only as it’s needed. 
  3. Heat pump water heaters: These energy-efficient heaters transfer heat from the air or ground to heat water, drastically reducing the amount of electricity required. 

Did you know Superior Plumbing also offers commercial plumbers Perth services. Learn more. 

Storage tank water heaters 

Storage tank water heaters, the most common type found in households, maintain a reservoir of hot water that is heated and stored for use when needed. They are designed to provide a large volume of dependable, low-cost hot water.  

Basic components of storage tank water heaters: 

  • The tank: The heavy metal tank, usually made of steel, has a protective inner lining to resist rust and corrosion. The capacity of the tank varies depending on the model, typically ranging from 75 to 300 litres. 
  • Insulation: Surrounding the tank is a layer of insulation to help keep the water hot with minimal energy usage. The efficiency of the insulation significantly influences the standby energy loss of the unit. 
  • Heating mechanism: This could be an electric resistance heating element or a gas burner, depending on the model. Electric models have one or two heating elements, while gas models have a burner and chimney system. 
  • Thermostat: This device controls the temperature of the water inside the tank. When the water temperature drops below the set level, the thermostat activates the heating element or burner. 
  • Dip tube: The water supply pipe that delivers cold water to the bottom of the tank. 
  • Heat-out pipe: Located at the top of the tank, it allows hot water to exit and flow through the home’s plumbing. 
  • Pressure relief valve: An essential safety device that releases pressure if it exceeds a preset level. 
  • Drain valve: Positioned near the bottom of the exterior tank, it allows for easy draining, flushing of sediment, or replacing the unit. 
  • Anode rod: This rod, made from magnesium or aluminium with a steel core, helps to prevent tank corrosion. 

Working mechanism of storage tank water heaters 

When a hot water tap is opened, hot water exits the tank and is replaced by incoming cold water, which is heated at the bottom. The thermostat activates the heating mechanism as needed to maintain the preset temperature. Heated water rises to the top, ensuring a steady supply of hot water. 

Safety features 

Storage tank water heaters feature a pressure relief valve that releases excess pressure to prevent damage or explosions. In gas models, a flue expels combustion gases from the heater to the outside, ensuring safety. 

Tankless water heaters  

Tankless water heaters, often referred to as demand-type or instantaneous water heaters, offer a modern, energy-efficient alternative to traditional storage tank heaters. Unlike their counterparts, tankless heaters do not store a large volume of hot water; instead, they heat water directly as it flows through the unit. 

Key components of tankless water heaters: 

  • Heat exchanger: This is a device that transfers heat from one source (either an electric element or a gas burner) to the water flowing through the unit. It’s activated by the flow of water when a hot water tap is opened. 
  • Temperature sensors: These monitor the incoming water temperature and the outgoing water temperature to determine how much heat is needed. 
  • Modulating gas valve (in gas models): This adjusts the amount of gas delivered to the burner, matching the heat needed to maintain the desired water temperature. 
  • Electric elements (in electric models): These heat the water as it passes through the exchanger. 
  • Flow sensors: These detect when a hot water tap is turned on and off, triggering the heater to start and stop heating. 
  • Venting components (in gas models): Gas models require an air supply for combustion and a venting system to expel the combustion gases safely. 
  • Inlet and outlet water connections: Cold water enters the unit through the inlet, and hot water is delivered to the tap through the outlet. 

Operation of tankless water heaters 

When a hot water tap is opened, a tankless heater’s flow sensor triggers the heating mechanism. Water is directly heated as it passes through the heat exchanger, with temperature sensors adjusting the heat to maintain a steady output. When the tap is closed, the unit enters standby mode, reducing energy use. 

Considerations and limitations 

Tankless water heaters, while energy-efficient, can struggle with multiple simultaneous demands due to limited flow rates (8–19 litres per minute). Gas models generally offer higher flow rates than electric ones. To manage high demand, some homes install multiple tankless heaters dedicated to specific appliances or areas. 

Heat pump water heaters 

Heat pump water heaters, or hybrid water heaters, represent an innovative approach to domestic water heating. Instead of creating heat directly, these systems use electricity to transfer heat from a relatively low-temperature source (air or ground) to heat water, a process that is more energy-efficient than conventional methods. 

The components of heat pump water heaters: 

Heat pump water heaters consist of two main components: a heat pump, which is responsible for heat extraction, and a storage tank that holds the heated water. Here’s a more detailed look at how they function: 

  • Heat absorption: The system starts with the heat pump extracting heat from the surrounding air or ground. A fan pulls air into the unit and over an evaporator, which contains refrigerant. As the air passes over the evaporator, the refrigerant absorbs heat from the air and evaporates, transforming from a liquid into a gas. 
  • Heat transfer: The now-heated refrigerant gas is compressed in a compressor, increasing its temperature further. This hot refrigerant then passes through a condenser, which is wrapped around the water storage tank. The heat from the refrigerant is transferred to the water in the tank, heating it up. 
  • Cooling and reuse: After transferring its heat to the water, the refrigerant cools down and turns back into a liquid. It then returns to the evaporator to begin the cycle anew. 
  • Back-up heating: In periods of high hot water demand or when the ambient temperature is too low for efficient heat extraction, an electrical resistance heater kicks in. This element is located inside the tank and works like those in a conventional electric water heater, heating the water directly. 

Mechanism of heat pump water heaters 

Heat pump water heaters use electricity to transfer environmental heat to water. When hot water is needed, the heat pump activates, heating water via a refrigerant and heat exchanger. Upon reaching the set temperature, the system goes into standby mode. An auxiliary heater assists during high demand or cold conditions. 

Efficiency and considerations 

Heat pump water heaters, being 2–3 times more energy-efficient than conventional ones, are ideal for Perth’s warm climate. They transfer heat, using less energy, but need a backup in colder months. Installation requires a space with temperatures between 4.4°C and 32.2°C and enough air around the heater. Though taller than traditional heaters, their energy efficiency makes them an excellent option for Perth’s residents. 

The importance of regular maintenance 

Keeping a hot water system in optimal working condition requires regular maintenance. While some homeowners might feel comfortable undertaking basic tasks, many will benefit from the expertise and convenience provided by a professional service. Superior Plumbing Drainage & Gas, with its team of trained professionals, can provide comprehensive services to help Perth homeowners maintain and improve the efficiency of their hot water systems. 

Regular maintenance and inspection  

Superior Plumbing Drainage & Gas conducts regular maintenance checks to ensure that your hot water system is functioning optimally. This includes: 

  • Flushing the tank: Over time, sediment can accumulate at the bottom of your water heater tank, causing it to work harder and potentially shortening its lifespan. The team at Superior Plumbing can flush your tank every six months to a year, as needed, to prevent this build-up and improve the efficiency of the system. 
  • Checking the pressure relief valve and thermostat: The pressure relief valve is a critical safety feature in your water heater, which helps prevent pressure build-up. Along with the thermostat, which regulates water temperature, it’s essential to ensure these components are working correctly. Superior Plumbing’s professionals can conduct regular checks and make necessary adjustments or replacements. 
  • Inspecting and replacing the anode rod: The anode rod in your water heater is designed to attract corrosive elements, preventing them from damaging the tank. It’s generally recommended to check this rod every two years, and the experts at Superior Plumbing can replace it when necessary to extend the life of your hot water system. 

Expert consultation and replacement services 

If you’re considering upgrading your current water heater or need advice on choosing the best system for your needs, Superior Plumbing Drainage & Gas can provide expert consultation based on our extensive knowledge and experience. We can help guide you to the most efficient and cost-effective solutions, such as tankless or heat pump water heaters, especially suited to Perth’s climate. 

Furthermore, if your water heater needs replacement, Superior Plumbing provides hassle-free installation services, ensuring that your new system is installed correctly and safely. Whether you require routine maintenance, repair, or a complete system replacement, our team can provide professional and reliable service to ensure you always have hot water when you need it. Learn more about our hot water plumbing and repairs. 


Understanding how your hot water system works can help you make informed decisions about maintenance, repair, and replacement. It’s essential to schedule regular inspections and services to keep your system running efficiently and extend its lifespan.  

With Superior Plumbing Drainage & Gas, you can rest assured that your hot water system will remain in top condition, providing reliable and efficient service for your home. We offer our services to Perth and its surrounding areas—if you need a plumber in Booragoon, Claremont, Fremantle, Armadale or any other Perth area, reach out to us today for all your hot water system needs.