Bosch Gas Hot Water System Troubleshooting: Your Ultimate Guide

Bosch hot water systems are known for their efficiency and reliability, but they can sometimes encounter issues, just like any other gas appliance.

In this ultimate guide, we will discuss common problems your hot water pipe might face and provide you with Bosch gas hot water system (HWS) troubleshooting tips to help you diagnose and potentially resolve these issues.

However, it is essential to hire a professional service technician to ensure that your water heaters are safe and running to their full potential.

How Does a Bosch Gas HWS Work?

A Bosch gas hot water system functions on the principle of heating water using natural gas or liquefied petroleum gas (LPG), providing a steady source of hot water whenever needed. Here’s a basic rundown of the workings of these devices.

  • Starting the heating process: To start, the entire process is initiated when a hot water tap in your home is turned on. This action sends a signal to the water heater, indicating that hot water is required.
  • Gas flow and water channeling: Once this message is conveyed, the gas control valve on the hot water system opens, allowing gas to flow into the burner. Simultaneously, the water is channeled from your home’s water supply through a pipe into the heat exchanger.
  • Heating the water:  The gas burner ignites, and the heat generated from this ignition is transferred to the water through the walls of the heat exchanger. The heat exchanger is an integral part of the system that allows for the efficient transfer of heat from the burning gas to the water. This heating process elevates the temperature of the water without any direct contact between the water and the combustion gases, ensuring safe operation.
  • Hot water supply: As the hot water is produced, it’s directly sent to the open hot water tap, providing a steady flow of hot water for your use. The gas hot water system continues this operation until the hot water tap is turned off, reducing waste and ensuring energy efficiency.
  • On-demand hot water: One of the standout features of a Bosch gas hot water system is its ability to heat water “on demand”. Instead of storing a large volume of hot water in a tank, gas instantaneous models heat water as it passes through the unit, saving energy by only heating the water you need, when you need it.
  • Special features: Note that while the process outlined above is a simplified general explanation of how a Bosch gas hot water system works, different models may come with their unique features and mechanisms, such as temperature controllers or compatibility with solar water heating systems. Always refer to your user manual or contact a professional if you have specific questions about your particular model.
  • Maintenance and safety: Regardless of model, remember that any maintenance or repairs on a gas hot water system should be carried out by a certified technician to ensure safety and proper operation. Now that you have a basic understanding of what the Bosch gas hot water system is and how it works, it’s time to finally explore the common issues it has and what you can do with it.

Man adjusts a gas hot water system

Problem 1. No Hot Water

Experiencing no hot water can be frustrating, especially during cold weather. There could be several reasons behind this issue, such as gas supply problems or a malfunctioning pilot light.

Check Other Gas Appliances

The first step in troubleshooting your Bosch hot water system is to ensure the gas supply is not the issue. Check other gas appliances in the house, such as a gas stove, to confirm that they are operating correctly. If other gas appliances are not working, this could indicate a gas supply problem, which will require contacting your gas company.

Check Pilot Light, Gas Valve, and Mains Power

Another common reason for no hot water is a pilot light that has gone out. Consult your user manual for instructions on how to relight the pilot light. Additionally, ensure that the gas valve is in the “on” position. Also, check the power point where the hot water unit is plugged in to ensure proper electricity supply. If in doubt, consult an expert or contact Bosch for guidance.

2: Insufficient or Fluctuating Hot Water

At times, you may face issues with inconsistent hot water supply, which could be due to variations in water pressure or issues with the heat exchanger. Identifying the reasons can help you tackle them effectively.

Check Water Pressure and Flow Rates

An inconsistent flow of hot water may be due to variations in water pressure or flow rates from hot water taps. Make sure that the water pressure and flow rates in your house are consistent by testing all hot water taps. If the water pressure and flow rates are not the same throughout the house, you may need to consult a professional plumber to resolve the issue.

Check the Heat Exchanger

Another possible cause of insufficient hot water is a blocked or malfunctioning heat exchanger. The heat exchanger is a critical component of your Bosch hot water system, as it transfers heat between the gas burner and the water. It is essential to service this part regularly and hire a professional service technician to clean or replace it if needed.

3: Water Temperature Too High or Too Low

Problems with water temperature can be uncomfortable and may lead to potential safety hazards. Learn how to adjust the controller or identify issues with the cold-water pipe to address these concerns.

Adjust the Controller

A Bosch hot water system can be adjusted to the desired water temperature by turning the controller knob. Check your user manual for specific instructions on how to set and adjust the temperature of your Bosch water heater. If the problem persists even after setting the correct temperature, this could indicate a manufacturing fault, and you should contact Bosch for assistance.

Check for a Blocked Cold-Water Pipe

A too-hot water temperature could also be caused by a blocked cold-water pipe. Confirm that the cold-water supply is not impeded and that the hot and cold-water pipes have not been mixed up during installation. If unsure, consult a professional plumber to inspect and fix any issues with the plumbing system.

A plumber works on a gas hot water system

4: Water Leaks or Gas Leaks

Leaking water or gas from your hot water system can lead to damage and health hazards. Learn how to identify the source of the leak and seek professional help to resolve the issue.

Identify the Source of the Leak

Leaking water or gas can not only cause damage to your house but can also be a hazard to your health. If you detect a leak around your Bosch hot water unit, first attempt to determine the source of the leak. Water leaks could be caused by a damaged water valve or a loose connection, while gas leaks could stem from a faulty gas valve or old, worn-out connections.

Remember, gas leaks can be dangerous, and it is always advisable to seek professional help when dealing with them.

Contact a Professional

If you are unable to resolve the issue or find the source of the leak, shut down your Bosch hot water system and contact a professional service technician to resolve the problem safely and efficiently.

Always Consult the Manual

While this guide covers some essential Bosch gas hot water system troubleshooting tips, we cannot overemphasise the importance of involving a professional service technician when facing issues with your hot water system.

They have the knowledge and experience required to diagnose and resolve problems accurately, ensuring your system is safe and efficient.

For further assistance or information, consult your user manual or visit the Bosch website for additional resources on your specific hot water system model.

Bosch Gas Hot Water System Troubleshooting

Experiencing issues with your Bosch gas hot water system? The following error codes suggest basic actions to rectify these.

Keep in mind that although these quick fixes can be tried at home, it’s crucial to consult a trained professional for a thorough diagnosis and repair if problems persist.

Code 11

  • Problem: Unit ignition fault.
  • Solution: Confirm the gas valve is open and the supply is adequate. Test this by lighting the gas stove; if it fails to light, the supply is likely compromised.

Code 29

  • Problem: Blockage in the unit’s neutraliser.
  • Solution: Attempt to reset the controller by switching off the main power, and then switching it back on.

Code 90

  • Problem: Abnormal combustion or low gas supply pressure.
  • Solution: Shut off the control unit, activate the hot water tap, and then turn on the control unit.

Code 92

  • Problem: The water heater’s neutraliser needs replacement.
  • Solution: Contact a plumber to replace the neutraliser.

Code 99

  • Problem: The hot water system has shut down due to abnormal combustion.
  • Solution: If a power cycle (off and on) doesn’t resolve the issue, seek help from a qualified plumber experienced in hot water systems.

Code A0

  • Problem: Issues with your heater’s hot and cold sensors.
  • Solution: Shut down the unit, turn on the hot water tap, and then power the unit up again.

Code A1

  • Problem: Excessive temperature within the hot water unit.
  • Solution: Resolve the A1 code by enlisting a qualified plumber.

Code A4

  • Problem: The air temperature sensor is malfunctioning.
  • Solution: Clear the A4 code by contacting a qualified plumber.

Code A7

  • Problem: The water temperature sensor is malfunctioning.
  • Solution: Get a qualified plumber to rectify the A7 code.

Code A9

  • Problem: No hot water or fluctuating temperatures.
  • Solution: Power off the unit, turn on the hot water, and power on the unit again. If unsuccessful, verify the gas supply pressure.

Code C1

  • Problem: Insufficient airflow prevents the heater from starting.
  • Solution: Fully open the hot water tap, then shut it off. Power the system off and on afterwards.

Code C7

  • Problem: The fan is faulty, restricting water use to cold only.
  • Solution: Clear the C7 code by reaching out to a qualified plumber.

Working on a gas hot water system

Achieve Reliable Hot Water with Bosch

This Bosch gas hot water system troubleshooting guide provides a basic understanding and first-aid solutions for common issues.

Despite their reliability, these hot tap systems may sometimes need expert attention. It’s strongly recommended to engage professionals for precise diagnoses and safe, effective repairs.

Also, don’t overlook the wealth of information that your user manual and the Bosch website provide. Becoming familiar with potential issues can help extend your system’s lifespan, ensuring your home always remains warm and comfortable.

Please note: This information is provided for advice purposes only. Regulations differ from state to state, so please consult your local authorities or an industry professional before proceeding with any work. See Cyber Plumbers’ Terms & Conditions here.

Need a Plumber?

Local Plumbers available 24/7

Recent Posts

The Cyber Group is on call for all plumbing, air conditioning and electrical needs over ...

Discover common causes of low water pressure at home and learn how to fix them. ...

Discover the top benefits of installing a gas cooktop: precise temperature control, cost-effectiveness and durability. ...

Find practical solutions for common bathroom plumbing problems like clogged drains, leaky taps, running toilets, ...

Discover the benefits of bidet installation for enhanced hygiene and eco-friendliness. Learn how to choose ...

Dotted Map of Service Areas

Plumber NEAR ME

Local Plumbers Near You

Looking for a trusted and experienced plumber to help you get out of a plumbing dilemma in your home? Cyber Plumbers is here and ready to help. We can do it all, from fixing a burst pipe in the kitchen to unclogging a blocked drain in the bathroom. If you’re building a new home or renovating an existing property, we can even assist with installing new hot water systems as well as countless other essential plumbing services. Best of all? Our team of certified and experienced plumbing contractors are just around the corner!

FIND A Plumber


Our Simple Process

Simply give us a call and let us know your problem. Or book online.

Our technicians will give you a fixed up-front cost, meaning you will always know the price before we start any work.

Pay after the work is done, only when you are completely satisfied with the service.