See how your water heater works.

In this atmospheric gas tank, a burner adds heat below the stored water. Combustion gases rise through the central flue and continue through the vent toward the outdoors. The tank supplies hot water while the controls call for reheating as needed. Other gas designs have different venting arrangements.

Tank & insulation

The inner vessel stores water under pressure. A protective lining and surrounding insulation serve different purposes: the lining helps protect the steel, while insulation slows heat loss between uses.

Cold in, hot out

Opening a hot tap draws water from the upper part of the tank. Incoming cold water travels down the dip tube toward the bottom, where it can be heated for later use.

Burner & gas control

The gas control responds to water temperature and regulates fuel delivery. When heating is needed, combustion at the burner transfers heat to the tank through the appliance’s design.

Flue & draft hood

In this natural-draft design, combustion gases rise through the central flue and draft hood into the vent. That entire route and the available combustion air are part of safe operation.

Corrosion & pressure protection

The anode is a consumable part that helps protect the tank from corrosion. The temperature-and-pressure relief valve serves a separate purpose: it can release water when its rated limit is exceeded.

This electric tank uses upper and lower resistance elements to add heat to stored water. Thermostats call for heating as temperatures change. The tank and heating capacity work together to supply the household; this design has no gas burner or combustion flue.

Tank & insulation

An insulated vessel stores water under pressure. The outer jacket covers the assembly, while insulation reduces heat escaping into the room between periods of use.

Cold in, hot out

The dip tube directs new cold water downward as hot water leaves from the upper outlet. This arrangement helps separate the incoming supply from the stored hot water.

Upper & lower heating elements

The submerged elements turn electrical energy into heat at different heights in the tank. The controls determine their operation; another model may use a different arrangement.

Thermostats & high limit

Thermostats respond to water temperature during normal heating. A separate high-temperature cutoff interrupts operation if its limit is reached, providing protection beyond the everyday thermostat setting.

Anode & relief valve

The anode helps limit corrosion of the steel tank. The temperature-and-pressure relief valve protects against a different condition: excessive temperature or pressure. Neither replaces the normal heating controls.

A heat pump transfers warmth from room air into the tank. The fan, evaporator, compressor and condenser carry out that heat-transfer cycle. This hybrid example also has resistance elements that can add heat when its controls call for them. Room conditions and household demand affect performance.

Insulated storage tank

The insulated storage vessel sits below the heat-pump assembly. It holds the heated water while the system replenishes heat as needed. Stored volume and recovery together determine how it serves the home.

Fan & evaporator

The fan moves room air across the evaporator, where refrigerant absorbs heat. Air leaving this stage is cooler, and moisture can condense from it during operation.

Compressor

The compressor uses electricity to raise the pressure and temperature of refrigerant vapor. That makes it possible to transfer heat into the water. Refrigerant stays in its own sealed circuit.

Condenser coil

In this example, a coil around the tank wall releases refrigerant heat into the stored water. The two fluids remain separate. Other models may arrange the heat exchanger differently.

Supplemental electric elements

Resistance elements provide an additional way to heat the tank. The selected mode, water demand, room conditions and model controls determine when they are used.

Controls & tank protection

Sensors give the controller information to coordinate heat-pump and resistance heating. The relief valve provides separate temperature-and-pressure protection regardless of the selected operating mode.

This condensing gas example heats water while it flows through the unit. Controlled combustion supplies two heat exchangers, including a secondary stage that recovers additional exhaust heat. Available hot-water flow depends on demand and the required temperature rise. The illustration represents a layout; actual models vary.

Cabinet & support frame

The front cover and support frame enclose the working components. They separate in the illustration so you can understand the layout. Keep actual equipment closed during normal use.

Combustion fan & burner

The fan supports combustion airflow, while gas controls supply the burner. Intake and exhaust connections provide separate paths as the system creates heat for the exchangers.

Dual stainless-steel heat exchangers

The primary exchanger transfers combustion heat into flowing water. The secondary recovers more heat from the exhaust, cooling it enough for water vapor to condense.

Water connections & flow sensing

Cold water enters the heater, passes through the internal water path and leaves through the hot outlet. Flow sensing tells the controls when and how much water is moving.

Electronic controls & display

The control board uses sensor information to coordinate heating. The display reports operating status and faults so a technician can investigate the condition in context.

Condensate collection

Recovering exhaust heat causes water vapor to condense. The trap is part of the route that collects and drains that condensate, separate from the household’s drinking-water supply.