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7 Common Bosch Hot Water Problems

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Bosch is one of the most well-known manufacturers of hot water systems worldwide but we have some tips on common issues

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Renowned for high-quality products, Bosch hot water systems rarely succumb to problems, but they are not entirely impervious. CDL Plumbing will outline seven of the most common Bosch instantaneous hot water problems and how you can identify them. It is imperative you get onto fixing any Bosch hot water heater problems as soon as they arise, as a faulty hot water system can not only be an inconvenience but, depending on the issues, can end up costing you money and time in the long run.

The Bosch Website recommends a safety and service inspection on all hot water systems at least every 2 years. For a recommended service Checklist, check the Bosch website, or in the manual that would have come with your system. This checklist will be completed by your CDL plumber.

Bosch Hot Water Heater Problems – Standard and Tankless

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Bosch manufactures a series of tankless water heaters alongside their standard range. As the name suggests, these systems provide an endless stream of hot water simply from a connection to a central water supply. Tankless systems make use of an “on-demand” process that gives the user hot water when they need it in a more energy and cost-efficient way.

Like all Bosch products, these tanks are covered by a warranty that takes care of any issues that might arise. Tankless hot water systems are subject to a different set of issues that require alternative troubleshooting methods. Here are some of the most common issues we see with these systems:

1. Leakage in The Gas Line

A leak in the gas line is a serious issue that will not only affect your hot water temperature but is dangerous for everything around the Bosch hot water system. The most common symptom of a gas leak is a smell near the pipes. It is vital that if you even slightly suspect a gas leak is involved, turn off electrical appliances nearby and call your local qualified gas plumber straight away.

2. Damaged Gas Valve

A damaged gas valve is an issue of equal importance to a gas leak. The gas valve controls the supply of gas into the Bosch system. If this is damaged, it will affect the flow of gas into the system and cause issues with temperature or cause total machine failure. A damaged gas valve is serious, and you should call a plumber immediately if you think your gas valve is damaged.

3. Issues with Water Flow

Water flow issues can stem from external factors from plumbing on the street. However, if the pipes connected to your hot water system aren’t correctly linked to one another, this can affect the pressure delivered through your water outlets. Seeing a sudden dip in pressure or fluctuations over some time is a common indication that there is an issue with the water pressure to do with your water heater.

An alternative cause of this problem is that too many applications are being used simultaneously. The solution to this is simple; you will need to upgrade your system to work with an increased water capacity.

4. Accumulation of Sediment

A Bosch system will invariably see mineral sediment build up throughout the machine’s lifetime. Mineral deposits can accumulate at the base of the water heater. Whilst not the most detrimental to your system, if left untreated for an extended period of time, you will see a drop in water quality and pressure. It is best to be on top of this as soon as you start to notice any changes and call in a professional to clean out the pipes.

5. Defective Thermocouple

A damaged thermocouple is one of the more prevalent Bosch instantaneous hot water problems. Thermocouples are designed to detect if a pilot light loses its heat and subsequently close the gas valve to prevent a gas leak. A working thermocouple is crucial to generating hot water, and because it involves gas, it is important to call a licensed professional if it becomes damaged.

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The thermocouple is a device that will shut off the gas supply to the water heater if the pilot light ever goes out. A simple function that is vital for safety. A Thermocouple generates a tiny amount of electrical current when heated by a flame. This small amount of electrical current will keep the pilot gas valve open. Should the pilot go out, the electrical current will stop and the gas valve will close.

6. Issues with The Pilot Light

Issues with the pilot light stem from previously mentioned issues with the gas valve or thermocouple. However, often the pilot light can extinguish for other external reasons. It is possible to relight the pilot light on your own by meticulously following the Bosch manual, but this is not recommended. Any pilot light-related Bosch hot water problem must be looked at by a licensed plumber.

7. Fluctuating Water Temperature

Sporadic temperature changes are another known Bosch hot water problem. Often the cause of this is an issue with the gas, including an undersized gas bottle or a faulty gas meter diaphragm. Otherwise, your system may have a defective showerhead or restrictor that is affecting the ability of the tap to register as a hot water outlet. This issue can be quickly diagnosed by a plumber and fixed.

How to Avoid Further Bosch Instantaneous Hot Water Problems

Much of what you can do with your Bosch hot water system involves close monitoring and being aware of what to look for with your system to identify any issues arising especially leaks. Ensure you are regularly cleaning out sediment and inspecting the condition of the heater as you use it. Your Bosch hot water system will have a long life if cared for properly and monitored for problems and so will require a lot less servicing and maintenance.

It is important to remember that most DIY plumbing is illegal in NSW. It is not only dangerous to attempt to fix severe gas and water issues without proper training, but it will also void your insurance should any further damage occur, so best to leave it to the professionals – like CDL Plumbing.

Solve Your Bosch Instantaneous Hot Water Problems with CDL Plumbing

CDL Plumbing boasts over 15 years of experience helping our customers with all Bosch hot water problems. There’s no doubt about it – Bosch delivers fantastic hot water systems and will work well in every setting, but sometimes things can go wrong.

If you’ve noticed any problems with your Bosch hot water system, then it’s time to turn to the professionals. It’s better to get the experts in to fix a small issue before it becomes a serious one. For any and all Bosch hot water heater problems in Newcastle, Lake Macquarie, and the surrounds, turn to CDL Plumbing today. Contact our team today on 0477 76 2937 for the best advice on your Bosch hot water systems or for help with gas hot water systems in general.


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Simple, we have an excellent reputation, are fully qualified and licensed and we love what we do. We don’t claim to be the cheapest, but we are reliable, friendly and one of the best plumbing companies in Newcastle and NSW.

Get Your Bosch Water System Problems Fixed Today By A Local Certified Plumber

Book A Local Heating Engineer

Call Us: 0477 76 2937

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Based on 72 reviews

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CDL Plumbing & Drainage are expert plumbers and gas fitters servicing Newcastle & Lake Macquarie from our Gateshead HQ. We have over 15 years of experience and specialise in all domestic and commercial plumbing, able to take on large-scale drainage projects. Fully qualified (Level 4), licensed & insured with free quotes. We have 2 teams of friendly and reliable plumbers with fully equipped vans.

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