How Does a Gas Hot Water System Work?

Many homeowners prefer gas hot water systems. They are more consistent than electric ones, which can experience temperature swings. But how does a gas hot water system work?

In short, it burns natural gas to heat a heat exchanger, which then heats the water, with a thermostat controlling the temperature.

So, is a gas system the right choice for your home? Let’s look at what it is, along with its pros and cons, so you can discuss it with your gas hot water installation service before deciding. Read on!

What is a Gas Hot Water System?

A gas hot water system is a setup where a gas burner heats up your water. The burner creates controlled flames, and then a heat exchanger transfers that heat to the water without direct contact.

These systems are designed to deliver hot water whenever you need it. They supply taps, showers, appliances, and fixtures. This makes daily activities like bathing, cooking, and cleaning more convenient.

Unlike electric hot water systems that use heating elements, gas-fired water heaters burn natural gas or propane to generate heat. Their steady flame heats water faster, giving you hot water quickly.

In general, there are two main types of gas hot water systems: storage tank and tankless systems.

Storage tank systems usually hold about 30 to 80 gallons of hot water. So you have a steady supply whenever you need it. In a gas storage hot water system, the heated water is kept in an insulated tank.

They’re ideal for larger homes with high hot water demand, as they can serve multiple fixtures at once without running out.

Tankless systems, or instant hot water systems, heat water only when you need it. This on-demand approach saves energy by avoiding standby heat loss.

They also save space and tend to last longer because they have fewer parts exposed to constant heat.

How Do Gas Hot Water Systems Work?

Here are the main steps showing how a gas hot water system works:

1. Gas Supply — Natural gas or propane enters the water heater through a dedicated pipe. It passes a manual shut-off valve and a pressure regulator, which lowers and steadys the pressure for the burner to operate well.
2. Thermostat Call — A temperature sensor inside the tank keeps track of the water temperature. When it drops below your setpoint, the thermostat control opens the gas control valve. This allows fuel to reach the gas burner ignition.
3. Ignition — When the thermostat calls for heat, the gas control valve sends fuel to either a standing-pilot or an electronic ignition. In standing-pilot models, a small flame keeps a thermocouple warm. In electronic units, a hot-surface igniter or a spark lights the main burner immediately.
4. Combustion — Gas and combustion air mix at special burner ports. This creates a steady flame. The fuel and air amounts are carefully adjusted for efficient and clean burning. This controlled burning releases a lot of heat directly into the flue tube or heat exchanger chamber.
5. Heat Transfer — Hot gases rise through the flue, heating the water. This heat moves through the metal walls. Then, the water circulates, warm water up, cool water down, until the tank reaches the right temperature.
6. Flame Sensing — A flame sensor, like a thermocouple or flame rod, constantly checks for the burner flame. If the flame goes out unexpectedly, it sends a signal to shut off the gas valve.
7. Safety Monitoring — Pressure and temperature sensors track tank conditions constantly. If water gets too hot or pressure rises too high, the relief valve opens to release steam and water. Draft-switch interlocks detect blocked or reversed vents and shut off the heat to keep everything safe.
8. Venting — Combustion gases exit the chamber and travel through the vent or flue. Properly sized and sloped pipes carry the exhaust safely outside above the roof, preventing back-drafting. In systems with a blower, the induced draft helps pull the gases out, ensuring reliable venting in all weather.
9. Burner Shutdown — When the thermostat feels the water is hot enough, it shuts off the gas valve, which puts out the flame. The fuel stops flowing, and the chamber seals shut. This automatic shutdown saves energy and keeps the tank at the right temperature until more hot water is needed.
10. Standby — After burner shutdown, the unit returns to standby mode. In standing-pilot systems, the pilot flame stays lit. In electronic-ignition models, all flames go out. The thermostat keeps checking the water temperature, ready to restart heating when the water drops below the setpoint.

That’s how a gas hot water system works (especially for the ones with the storage tanks). For a tankless system, it’s way simpler:

• When you turn on a hot water tap, cold water flows into the unit.
• A sensor detects the flow and ignites the gas burner.
• The water passes through a heat exchanger and is quickly heated.
• The hot water then flows directly to the tap.
• When you turn off the tap, the sensor shuts off the burner, stopping the heating.

What are the Advantages and Disadvantages of Gas Hot Water Systems?

You know what a gas hot water system is and how it works. So, before installing one, let’s look at its pros and cons:

Advantages of Gas Hot Water Systems

These are the reasons that might encourage you to install a gas hot water system in your home:

• Cheaper to run than electric systems because gas costs less per unit of energy.
• Gives hot water instantly and keeps it coming without running out.
• Heats water faster than electric tanks, so you don’t have to wait long.
• Takes up less space because it doesn’t need a big storage tank.
• Works even during power outages if it has a pilot light.
• Built strong to last 15-20 years if you take good care of it.
• Can be installed inside or outside and uses natural gas or propane.
• Very energy efficient, especially condensing models that reuse heat from the exhaust.
• Produces fewer greenhouse gases than electric systems that use coal power.
• Can be combined with solar or heat pumps to save even more on energy bills.

Disadvantages of Gas Hot Water Systems

These are the factors you should consider carefully before making the decision to install one:

• It costs more to buy and install initially.
• Needs a natural gas line or propane tank.
• Must have a vent or chimney.
• If not maintained, there’s a risk of dangerous carbon monoxide leaks.
• Needs regular check-ups to ensure it burns safely.
• Models with a pilot light use a small amount of gas continuously.
• Changes in gas prices can affect the running costs.
• You might need more than one heater for very large houses.

FAQ about Gas Hot Water Systems

Here are some key questions about the gas hot water system you should know:

Does gas hot water still need electricity?

Modern gas water heaters usually need electricity for ignition and controls. Older models with a standing pilot light don’t.

They run on a constant flame and work without power, as long as the pilot stays lit. Keep this in mind when planning for outages.

What is the lifespan of a gas hot water system?

A gas water heater typically lasts 10 to 15 years. Regular check-ups and cleaning can help it last longer.

Its lifespan depends on how you use it, how it’s installed, and your water’s mineral content. Proper maintenance and quick repairs make a difference.

Is it cheaper to have gas or electric hot water?

Gas hot water systems in Australia tend to be cheaper to operate. Natural gas costs less per unit of energy than electricity.

Although the upfront price of a gas system may be higher, the lower ongoing costs usually save you money in the long run.

How does a gas hot water heater work without electricity?

A gas water heater with a standing pilot runs without electricity. The pilot stays lit with minimal gas. When hot water is needed, the gas valve opens and ignites the main burner. A thermocouple acts as a safety switch, allowing gas flow only if the pilot burns.

Conclusion

Gas hot water systems are a good choice for reliable, quick, and energy-efficient hot water. They use natural gas to heat water fast, so you get hot water whenever you need it.

Choosing the right system means considering your home’s needs and budget. Since you know how gas hot water systems work, you can make an informed decision that best suits your household.

We hope this information is helpful. Remember to contact a trusted gas maintenance service when needed to keep your system safe.