Instant Gas Hot Water System Problems and How to Fix Them

No hot water or sudden temperature changes often mean your instant gas hot water isn’t working properly. These issues can disrupt your day, including showering, doing laundry, and cleaning.

When there’s a problem, it’s best to call a gas hot water installation service to fix it safely. However, knowing some common problems can help you identify what’s wrong and try simple fixes while you wait for help.

This article will explain everything you need to know about troubleshooting instantaneous gas hot water systems. Keep reading!

How Does an Instant Gas Hot Water System Work?

Before talking about the common problems with instant gas hot water systems, let’s first learn how gas hot water system works. 

Here’s how an instant gas hot water system works, step by step:

1. When you turn on the hot water tap, cold water enters the heater. A sensor detects this flow at about 1 to 2.5 litres per minute and instructs the control panel to start heating.
2. The system checks the safety parts to make sure everything is safe and working right. Once approved, a fan starts to bring in fresh air for burning and to vent out exhaust gases.
3. The gas valve opens and sends gas to the burner. A spark lights the gas, making a steady flame. Sensors monitor the flame to ensure safety.
4. Cold water moves through the heat exchanger, taking in the heat from the burning gas. Its design makes the heat transfer fast and efficient, so the water gets warm as it flows through.
5. Thermistors and sensors monitor the water temperature all around the unit. The control system opens or closes valves to keep the temperature steady at about 50°C.
6. Hot water moves through pipes to your taps and showers. Safety parts like mixing valves control the temperature to avoid scalding and stop dirty water from flowing back.
7. When you turn off the hot water tap, sensors detect no flow. The system then shuts the burner and closes the gas valve.

Common Issues with Instant Gas Hot Water Systems and How to Fix Them

If your instant gas hot water system isn’t working, check these common issues and fix them with the right steps:

1. No Hot Water

When your instant gas hot water system isn’t working, the most obvious problem is that you have no hot water.

Unlike traditional heaters, instant systems don’t store hot water in a tank. Instead, they heat water as it flows through the unit. This means they depend on all parts functioning correctly every time you turn on the tap.

Common issues include a power outage to the control unit, a closed or empty gas supply, or water flow being too low or high to trigger heating.

Here’s what you can do for instant gas hot water system maintenance:

1. Make sure other gas appliances have the gas turned on and are working.
2. Check the power outlet or turn on any circuit breakers that are off.
3. Clean the inlet water filter to remove any dirt blocking it.
4. Reset it. Turn off the power at the outlet, wait 30 seconds, then turn it back on.
5. If these steps don’t solve the problem, call a licensed plumber to check the ignition and other parts safely.

2. Lukewarm Water Delivery

Lukewarm water is when the water from your tap is neither hot nor cold. And this is one of the signals that your instant gas hot water system is not working.

Lukewarm water usually indicates an issue with the heating elements, thermocouple, or temperature control valve. Unlike a complete loss of hot water, it suggests the system is struggling to heat properly.

Here are some quick steps for instantaneous gas hot water system troubleshooting:

1. Check your thermostat and raise the temperature slightly, but stay below 50°C for safety.
2. Open a single hot tap fully. High flow can overwhelm the burner and result in lukewarm water.
3. Look at the display for error codes that show problems with overheating, thermostat, or pilot light.
4. Clean the water inlet filter to prevent dirt or debris from blocking flow in your instant gas hot water system.
5. Press the reset button to clear minor faults and restart the heating cycle.

3. Fluctuating Temperature

This is known as the “cold sandwich” effect in an instant gas hot water system. Hot water suddenly turns cold, then hot again. These temperature fluctuations can be uncomfortable and catch you off guard with cold bursts.

It happens when your gas hot water heater struggles to maintain a consistent temperature due to issues like fluctuating water flow, inadequate gas pressure, or faulty thermocouples.

So, what to do when your instant gas hot water system is not working properly due to fluctuating temperature?

1. Turn on the hot tap after a brief pause of about 5 to 10 minutes and note the patterns of change.
2. Make sure your gas supply is steady. Call a licensed gas fitter to check for gas pressure issues.
3. Clean the inlet filters, strainers, and aerators on your hot water taps and shower heads.
4. If temperature keeps changing, have a licensed plumber inspect and replace any broken parts.

4. Low Water Pressure

Did you notice a weak flow from your hot water tap? It makes showers less fun and washing dishes take longer.

Your gas hot water system needs enough water to flow through the pipes, including the cold water inlet and hot water outlet. If the flow slows down, it might not heat correctly or might turn off.

Low flow often comes from clogged inlet filters, mineral buildup, or pipe leaks. Issues with the pressure regulator can also decrease flow and make your system not work well.

If this happens, you can try these steps to improve low water flow or pressure:

1. Turn on the cold tap fully and compare its pressure to the hot water to check for hot water system issues.
2. Shut off your water and check the inlet filter for dirt or trash.
3. Check taps and shower heads for clogs or flow restrictors, and keep aerators and filters clean.
4. Make sure your water pressure regulator is set the right way or checked by a professional.
5. Don’t use more than one outlet at the same time to keep the water flowing smoothly and prevent pressure drops.

5. Longer Time to Heat

This is also a common problem when your instant gas hot water isn’t working. You still have hot water, and it stays hot while you’re using it, but it takes longer to heat up.

This often happens because of problems with water flow, gas supply, or old parts that make the system slower to react.

For example, a blocked or dirty heat exchanger can cause mineral buildup, which slows down heating. Or, a faulty thermostat or flow sensor might misread the water flow or temperature, leading to delays.

To reduce longer heating times, try these steps:

1. Make sure there is enough gas supply because low pressure can make heating slower.
2. Turn on a hot tap and listen for a quick ignition sound like when you reignite the pilot light
3. Clean or change the inlet water filter so water can flow properly into the system.
4. Flush the unit to wash away mineral deposits and dirt that build up in the heat exchanger.
5. Check thermostat settings and raise the temperature if it’s too low.
6. Don’t run several showers or taps at the same time to help the heater work better.

6. System Trips

Your gas hot water system has safety features that shut it off if there’s a problem: a system trip. While it can be frustrating when hot water stops unexpectedly, these trips protect you from gas leaks and overheating.

Common causes include a faulty thermocouple, a blocked burner, or a clogged flue that restricts airflow. Also, faulty wiring or a malfunctioning control valve can also trigger the safety shut-off.

Here’s how to manage and troubleshoot system trips:

1. Check your power supply and reset any tripped circuit breakers connected to the heater.
2. Check around the controller, ignition module, and wires for any leaks or moisture.
3. Inspect vents, flues, and exhaust pipes for blockages or damage; clear debris if safe or call a technician.
4. If the system trips frequently or won’t reset, call a licensed plumber or gas fitter.

7. Higher Bills

This is also a common problem when your instant gas water heater isn’t working properly. When your gas bills increase, it usually means the heater is using more energy than it should.

Efficient systems can waste energy if the temperature isn’t set correctly. Hard water causes mineral buildup that clogs parts and hampers heat transfer. And multiple outlets can strain the system and increase gas use.

Here’s how to cut running costs when the instant gas hot water system isn’t working:

1. Track your hot water use. Do you take longer showers, do more laundry, or run the dishwasher more?
2. Set the thermostat between 50-60°C. Higher settings waste gas as the burner works harder to stay hot.
3. Check for leaks or hissing sounds. Small leaks waste gas and raise bills, often without clear signs.
4. Confirm if your unit fits your household, as mismatched systems use more gas for the same output.
5. Schedule regular maintenance to clean the system, remove mineral buildup, and boost efficiency.

FAQ about Instant Gas Hot Water Systems Problems

How to reset instant gas hot water systems?

If your gas hot water system isn’t working, reset it by turning off power and gas. Find the red reset button near the gas valve or thermocouple, press and hold for 5–10 seconds, then turn power and gas back on.

How to troubleshoot an instant gas hot water heater?

Sometimes, resetting your instant gas hot water system doesn’t solve the issue. Mineral buildup can block the heat exchanger and sediment may clog it. To maintain it properly, flush the system, clean the heat exchanger, and check for leaks. If problems persist, you can contact a professional plumber.

What is the life expectancy of an instant water heater?

A water heater usually lasts 15 to 20 years. Regular cleaning and flushing prevent mineral buildup and help it last longer. But, without proper maintenance, rust, dirt, and worn parts can cause it to fail sooner.

Conclusion

Nothing is more frustrating than running out of hot water or experiencing sudden temperature changes during a shower. These issues are often caused by broken thermostats, dirt build-up, or problems with the gas supply.

This article explains common problems with your instant gas hot water system and offers simple solutions. Some fixes you can do yourself, but others require a professional for safe repair.

At Melbourne Gas Plumber, we specialise in repairing gas hot water systems. Our experienced technicians quickly diagnose and fix issues, ensuring safety and convenience. Call us today to restore your hot water.