Bosch Tankless Water Heater Not Hot Enough [Gas & Electric]

The most common reasons behind Bosch tankless water heater not hot enough are:

  • Incorrect temperature setting
  • Gas that is not of the recommended type.
  • Plumbing crossover
  • Tripped heating module thermal cut-outs
  • Temperature dial set too low
  • High water flow rate, etc.

Also, clogged inlet filter screens or outlets or feeding preheated water to the heater can be the hidden reasons behind this problem. However, the problems can be different for both gas and electric tankless water heaters. 

In this guide, I’ll reveal the distinctive challenges that gas and electric water heaters bring to the table. Get ready for a riveting exploration of troubleshooting tips that will leave you empowered and your water piping hot!

Quick Solutions For Bosch Tankless Water Heater Not Hot Enough [Gas & Electric]

There are some reasons why a Bosch water heater not producing hot water and their corresponding quick solutions.

 Bosch Gas Water Heater

Inlet water filter cloggedClean any clogs or debris from the inlet water filter.
Temperature setting too lowAdjust the temperature setting to the appropriate level.
Plumbing crossoverInspect for any plumbing crossovers that may be affecting the water temperature.
Inadequate water flow rateVerify that the water flow rate is adequate to activate the heater, and clean any clogs or debris from the inlet water filter and showerheads.
Inlet gas particle screen clogged or damagedClean or replace the screen located at the bottom of the heater near the gas inlet.
Malfunctioning temperature sensorCheck the temperature sensor and replace it if necessary.
Wrong gas typeCross-check the gas type with the Bosch water heater manual recommended gas type.
High gas pressureInspect the gas pressure if it exceeds the recommended limit.

Bosch Electric Tankless Water Heater

Incorrect plumbing connectionsVerify plumbing connections. Check for correct and secure plumbing connections.
Tripped heating module thermal cut-outsRemove the cover and check the thermal cutouts. Verify continuity through each thermal cutout.
Low-temperature settingAdjust the temperature dial to the desired setting. Increase the temperature setting if needed.
Water flow rate issueMaintain a flow rate within the heater’s specifications. Ensure water flow remains within the recommended range.
bosch tankless water heater not hot enough

Bosch Gas Tankless Water Heater Not Hot Enough? [8 Easy Fixes]

In this section, I’ll explain all the reasons why you’re not getting enough hot water from your Bosch gas tankless water heater, along with their solutions. Have a look!

01. The Temperature Is Set Too Low

Bosch tankless water heaters allow you to set the temperature of the water that comes out of the unit. If the temperature setting on your Bosch tankless water heater is too low, you may not get enough hot water.

How To Fix:

Now the question is- how to adjust the temperature on Bosch tankless water heater. The front control panel of the water heater allows you to adjust the temperature of the hot water. 

The gas valve in the water heater is electronically controlled and adjusts the amount of heat the burner produces based on changes in the water flow rate and the temperature of the incoming and outgoing water.

The below steps are the part of bosch tankless water heater temperature adjustment troubleshooting guide:

Step 1: Locate the LED screen with the back error, up and down, OK, and power buttons on the front panel.

Step 2: The first step is to unhide the LM menu. The LM menu can be unhidden by touching the back arrow key. Then find the AU technical settings menu using the up and down arrow keys.

Step 3: Enter the passcode by using the up and down arrow keys. Select each number and hit OK to enter. After entering the passcode a green check mark will be shown. Then the display will return to the home screen. Touch the back arrow key to re-enter the menu. Then pressing the up and down arrow keys find the LM menu and touch OK. 

Step 4: You can adjust the temperature limit by touching the OK key with selecting the locked option. Then use the up and down arrow keys to adjust the value. 

Step 5: With the temperature, and limit set to the desired value you can press the OK key and then touch the back arrow key twice to return to the main menu. Now the temperature can be set at any value by simply pressing the up and down buttons.

02. Clogged Or Damage.d Inlet Gas Particle Screen

The inlet gas particle screen on a Bosch tankless water heater is an important component that helps prevent debris and dirt from entering the unit and blocking the gas flow. If the screen becomes clogged or damaged, it can restrict the gas flow and can lead to the Bosch tankless water heater not staying hot.

How To Fix:

The inlet gas particle screen is typically located at the bottom of the unit, near the gas supply line. Carefully inspect the inlet gas particle screen for any signs of blockage or restrictions. Look for debris, dirt, or other obstructions that may be preventing gas flow. 

If the screen is dirty or blocked, you can try cleaning it with a soft brush or compressed air. If the screen is damaged or cannot be cleaned, you may need to replace it with a new one. 

03. Debris Buildup On Inlet Filter Screen

The water filter screen is usually a mesh or screen filter that’s situated at the cold water inlet of a water heater. Its main function is to capture sediment and debris from the incoming water supply, effectively blocking them from entering the water heater tank.

water filter screen of bosch tankless water heater

By trapping sediment and debris, the water filter screen helps to ensure that only clean water enters the tank, promoting the efficient and safe operation of the water heater.

Debris can form on the inlet water filter screen of a Bosch tankless water heater for several reasons. One common cause is the presence of sediment or other contaminants in the water supply. Over time, these particles can accumulate on the screen and clog it, reducing water flow and potentially causing damage to the unit.

Another possible cause of debris formation is corrosion or mineral buildup within the water heater itself. As water passes through the unit, minerals such as calcium and magnesium can precipitate and form deposits on the inside of the pipes and other components.

These deposits can eventually break loose and become trapped on the inlet filter screen. When the filter gets clogged, water won’t be able to flow through it properly. So, the flow rate will be messed and you’ll get water that’s not as hot as your desired temperature.

How To Fix: 

If you want to solve your Bosch tankless water heater not heating problem, then it is essential to verify that the inlet filter screen is clean and undamaged. To clean the water filter screen properly, you should follow the below steps:

Step 1: First find the inlet water filter, which is typically situated at the bottom of the appliance on the right side of the cold water inlet fitting. 

Step 2: Next, turn off the water supply valve that is installed. 

Step 3: Next, open the discharge drain to clear the water. Remove the wire from the spring clip that secures the water filter screen in place. Once you have done that, you can take out the filter and examine it for any signs of damage or buildup. 

Step 4: If the filter is dirty, you should clean it, and if it is damaged, you should replace it with a new one to ensure that your water heater continues to operate safely and efficiently.

04. Obstruction-Free Water-Flowing Paths

It is important to inspect the water paths for any obstructions. To start with, it is important to inspect all the showerheads, faucet aerators, and whole house filters to ensure that there is no accumulation of debris. 

Over time, sediment and other particles can accumulate in these fixtures and filters, leading to blockages that can lead to the Bosch Tankless water heater not getting hot enough.

How To Fix: 

To check all showerheads, faucet aerators, and whole house filters for any debris on a Bosch water heater, you can follow these steps:

  1. Turn off the water supply to your water heater.
  2. Remove the showerheads and faucet aerators from your fixtures by unscrewing them.
  3. Check the showerheads and faucet aerators for any visible debris or buildup. If you see any, use a toothbrush or small brush to scrub away the debris.
  4. Check your whole house filter for any visible debris or buildup. If you see any, remove the filter and clean it according to the Bosch tankless water heater manual.
  5. Reinstall the showerheads, faucet aerators, and whole house filters, and turn the water supply back on.

05. Wrong Gas Type

Please verify that the gas type specified for the heater matches the type of gas being supplied. Using the incorrect gas type can result in your Bosch tankless water heater not producing hot water. Therefore, it is essential to verify that the gas type for the tankless water heater matches the gas type being supplied before installation.

How To Fix: 

Before proceeding with the installation, make sure that you have chosen the appropriate heater for the type of gas you will be using, whether it is Propane or Natural Gas. Check the rating plate of the heater and ensure that you feed it with the correct gas type to prevent your Bosch water heater not getting enough hot water problems.

06. High Gas Pressure

If the gas pressure exceeds the specifications recommended by the manufacturer, it may cause the water heater to not get hot enough. Therefore, it is important to regularly check the gas pressure and ensure that it falls within the range specified by the Bosch tankless water heater manual.

How To Fix:

Measure the inlet gas pressure and determine whether an adjustment is necessary based on the manufacturer’s recommended pressure range. To adjust the gas pressure when the inlet gas pressure falls outside of the recommended specifications, follow the procedure below:

Step 1: Shut off the gas supply to the water heater using the manual shut-off valve. Locate the inlet gas pressure port and unscrew the inside test port fitting. Attach a manometer to the test port fitting.

Step 2: Turn the gas supply back on and note the pressure displayed on the manometer. This reading is the static pressure. Test the dynamic pressure by turning on your water heater and setting it to P1 Max. Power mode.

Step 3: Before testing the water heater, make sure that all other gas appliances connected to the same gas piping system are turned on and running at maximum output, except for the heater. Then, open all the hot water faucets until the water flow rate reaches at least 6 gallons per minute (GPM). If the water heater switches to P2 mode, open additional hot water fixtures to maintain a sufficient flow rate and keep the heater in P1 mode.

Step 4: During the test, measure and record the lowest operating gas pressure, and make sure that it does not drop below 5 inches of water column (W.C.) for natural gas or 8 inches W.C. for LP (liquid propane). This pressure is dynamic pressure.

Step 5: Turn off the water heater and shut off the gas supply to the unit. Disconnect the manometer from the test port fitting and tighten the screw inside the fitting.

07. Plumbing Connection Crossover

If the hot water lines are unintentionally mixed with cold water due to a plumbing crossover, the resulting water temperature can be cooler than expected. This can occur when cold water enters the hot water lines, causing a decrease in temperature. One of the common causes of plumbing crossovers is failing single-lever faucet mixing valves.

How To Fix:

To check for a plumbing crossover in your water heater, you can take the following steps:

Step 1: Turn off the cold water supply to the water heater.

Step 2: Close the installer-supplied cold water shut-off valve. If there is no shut-off valve installed, it’s recommended to have one installed before proceeding. Open all hot water taps supplied by the water heater. This includes faucets, showers, and any other fixtures that receive hot water from the heater.

Step 3: Open all of the hot water taps that are served by the heater and wait for 10 minutes. Check all the hot water taps to ensure that there is no water flow. If you observe continuous water flow, small or large, it indicates a plumbing crossover, which needs to be corrected.

Step 4: To correct the crossover, seek help from a professional plumber. Once the crossover issue has been addressed, you can proceed to return the water heater to service.

Step 5: Reinstall the cover on the water heater. Open the inlet water supply to the heater to allow water to flow into the system. Open all hot water taps again to let the water flow through the pipes and fixtures. Keep the taps running until there is no more air coming out of the fixtures. This ensures that any trapped air is purged from the system.

08. Faulty Outlet Temperature Sensor

It is important to confirm that the outlet temperature sensor is firmly mounted on the hot water pipe and making good contact. Because the sensor is responsible for detecting the temperature of the water as it leaves the water heater. The sensor sends this information to the control unit, which then adjusts the water heater’s gas and water supply to maintain the desired outlet temperature.

If the outlet temperature sensor is loose or not making proper contact with the hot water pipe, it may not accurately detect the water temperature. This can result in the water heater supplying water that is not hot enough.

How To Fix:

If the outlet temperature sensor is not reading temperature correctly then you have to check the sensor properly. To ensure that the hot water temperature sensor is functioning properly, it is important to inspect its wiring regularly. Check for any signs of corrosion, damage, or loose connections. The wiring should fit snugly and be in good condition.

If you suspect that the hot water temperature sensor is not working correctly, you may need to measure its resistance readings. Consult your owner’s manual for specific instructions on how to do this for your particular unit.

If, after inspecting the wiring and taking resistance readings, you determine that the hot water temperature sensor is faulty, the temperature sensor should be replaced promptly to ensure the safe and efficient operation of the water heater.

Why Is Your Electric Water Heater Not Hot Enough? ( 4 Easy Fixes)

Here, I’ll outline the possible causes behind the inadequate supply of hot water from your Bosch electric tankless water heater and provide you with the appropriate solutions to address each issue. Take a look below for a comprehensive understanding.

Important Note: The neon light will be on whenever the electric heater does not produce enough hot water.

01. Incorrect Plumbing Connections

Incorrect plumbing connections can cause several problems with a water heater. Some of the common issues that can arise due to incorrect plumbing connections include:

Low water pressure: If the plumbing connections are not properly connected or if there are leaks, it can result in low water pressure. This can affect the performance of the water heater, causing reduced hot water flow and longer wait times for hot water.

Leaks: Incorrect plumbing connections can lead to leaks around the connections, causing water to drip or spray from the pipes or fittings. Leaks not only waste water but can also damage the surrounding areas, leading to structural damage or mold growth.

Inefficient heating: When the plumbing connections are incorrect, it can disrupt the flow of water through the water heater, causing inefficient heating. Insufficient hot water or water that doesn’t reach the desired temperature can be the result.

How To Fix:

To troubleshoot this problem follow the below steps:

Turn off the water supply: Locate the water shut-off valve connected to the water heater and turn it off. This will prevent any water flow during the reconnection process.

Verify plumbing connections: Inspect the plumbing connections to identify any incorrect or loose connections. Check both the cold water supply and hot water outlet connections.

Reconnect the water supply: If you find any incorrect or loose connections, disconnect them and reconnect them properly. Make sure the connections are secure and tightened according to the manufacturer’s instructions.

Turn on the water supply: Once the plumbing connections are verified and corrected, turn on the water supply by reopening the shut-off valve. This will allow water to flow into the water heater.

Check for leaks: After turning on the water supply, closely inspect all the connections for any leaks. If you notice any leaks, tighten the connections further or replace any damaged components as needed.

Restore power and test the water heater: Once you have confirmed there are no leaks, restore power to the water heater by turning on the corresponding circuit breaker. Allow the water heater to heat the water, and then test the hot water supply at various faucets to ensure it’s functioning properly.

02. Tripped Heating Module Thermal Cut-outs

When a thermal cutout trips in a water heater, it indicates that the temperature inside the heater has reached a level that is potentially damaging or unsafe. Tripping of thermal cutouts can cause several problems, including:

No hot water: If the thermal cutout has tripped, it may disrupt the heating process. Resulting in no hot water being produced by the water heater.

Insufficient hot water: In some cases, a tripped thermal cutout may only partially disrupt the heating process, leading to reduced hot water output. The water may not reach the desired temperature or may not stay hot for as long as expected.

Heater shutdown: When a thermal cutout trips, it typically triggers an automatic shutdown of the water heater. This is a safety feature designed to protect the unit from overheating and potential damage.

How To Fix:

To troubleshoot issues related to thermal cutouts, you can follow these steps to solve the issue:

Turn off the power to the water heater: Locate the circuit breaker or switch that controls the power supply to the water heater and turn it off to ensure safety during the troubleshooting process.

Remove the cover: Depending on the specific model of the water heater, you may need to remove the cover to access the thermal cutouts and other components. Follow the manufacturer’s instructions or use appropriate tools to safely remove the cover.

Locate the thermal cutouts: On top of each heating module, you should find thermal cutouts. These are safety devices that protect against overheating. They can trip in exceptional circumstances, and it’s important to check their continuity.

Check for continuity: Use a multimeter set to measure resistance (Ohms) to check the continuity through each thermal cutout. Place the multimeter probes on both sides of the cutout and measure the resistance. A continuity value of less than 0.5 Ohms indicates that the cutout is functioning correctly. If the continuity value is greater than 0.5 Ohms, it means that the cutout has tripped or is faulty.

Determine and resolve the cause: If a thermal cutout has tripped, it’s crucial to identify and resolve the underlying cause. Tripping can occur due to factors such as high temperature, restricted airflow, or other issues. Inspect the heating elements, ventilation, and any other relevant components to identify potential causes. If necessary, consult the water heater’s user manual or contact a professional technician for further assistance.

You will also need to check the inlet filter screen to see if it’s free of debris. Also, you have to make sure there is no passage of preheated water inside the heater. Because of these issues, it can cause the thermal cutout to trip.

Verify the inlet filter screen and outlets: Check the water heater’s inlet filter screen to ensure it is clear of debris. If there are any obstructions, clean the filter or replace it if necessary. Additionally, inspect all outlets served by the water heater, such as faucet aerators and showerheads, to ensure they are clear of debris that could restrict water flow.

Avoid preheated water: It’s essential to ensure that the water heater is not being fed with preheated water. This particular water heater is designed for cold water feed only. Verify that the water supply feeding into the heater is cold water, as feeding preheated water can impact the heater’s performance and lead to various issues.

03. Temperature Dial Set Too Low

If the temperature dial is set too low, the water heater will not heat the water to a sufficient temperature. This can result in a reduced hot water supply, especially during peak usage times or in colder climates.

Setting the temperature dial too low means the water heater needs to work harder and for longer periods to reach the desired temperature. This can result in increased energy consumption and higher utility bills.

How To Fix:

To increase the temperature of a water heater, follow these steps:

Locate the temperature dial: The temperature dial is typically located on the front of the water heater. It may be a knob or a dial with temperature markings.

Turn off the power: Before making any adjustments, it’s important to turn off the power to the water heater. Locate the circuit breaker for the water heater in your electrical panel and switch it off.

Adjust the temperature dial: Once the power is turned off, you can safely adjust the temperature dial. Turn the dial clockwise to increase the temperature setting. Most temperature dials have temperature markings or indicators that can help you select the desired temperature.

Test the hot water: Once the water has heated up, test the hot water at various taps to ensure the temperature is to your liking. Be cautious when using hot water, as higher temperatures can increase the risk of scalding. Remember to turn off the power before making any changes.

04. High Water Flow Rate

When the water flow rate is too high, the water may pass through the water heater too quickly, resulting in inadequate heating. The water may not have had enough time to absorb sufficient heat from the heating elements, leading to lukewarm or cold water.

Also, with a high flow rate, the water heater may struggle to maintain a consistent temperature. Fluctuations in temperature can occur, especially when multiple hot water outlets are being used simultaneously. In some cases, a water heater may have a maximum flow rate limit. If the actual flow rate exceeds this limit, the water heater may not be able to supply hot water at the desired temperature, resulting in reduced hot water output.

How To Fix:

Adjusting the water flow to stay within the water heater’s specifications is important to ensure proper operation and prevent potential problems. Each water heater has its own recommended flow rate, which is typically indicated in the manufacturer’s instructions or specifications.

Consult the bosch tankless water heater customer service center to determine the recommended flow rate for your specific model. This information will help you understand the desired water flow range.

Resetting Bosch Tankless Water Heater After Troubleshooting

You may need to reset a Bosch water heater after troubleshooting a problem with the unit not heating water sufficiently because the system may have automatically shut off as a safety precaution. 

Resetting a Bosch tankless water heater is a simple process that requires basic knowledge of electrical appliances. 

To reset the unit, all you need to do is press the red buttons on the thermal cutouts of the heating elements. Check out our guide on how to use Bosch tankless water heater reset button to learn more about it.


What is the temperature limit on Bosch tankless water heaters? 

The temperature limit on Bosch water heaters ranges from 100-120°F (38-58°C) depending on the specific model and type. Users can typically adjust the temperature but should do so carefully to avoid scalding and reduce wear on the unit.

Do Bosch tankless water heaters provide enough hot water?

Yes, Bosch tankless water heaters are designed to provide enough hot water for most household needs. Generally, most tankless water heaters can provide hot water at a rate of 2–5 gallons (7.6–15.2 litres) per minute, which is enough for most household needs.

Do Bosch tankless water heaters take longer to heat up?

The time it takes for Bosch tankless water heaters to heat water depends on its flow rate, power source, and incoming water temperature. Distance to the point of use also affects the time it takes for hot water to arrive.

Why is the Bosch tankless water heater heating slow?

It is true that Bosch tankless water heaters can take a bit longer to deliver hot water than traditional tank-style water heaters. it is because the water needs to be heated on-demand, as it flows through the unit, which can take a few seconds. 

Wrapping Up

In the guide, I’ve explained every possible problem with a solution related to your Bosch tankless water heater not hot enough issue. I believe, now you can fix the problem by yourself.

Besides, with proper maintenance of your water heater, you can avoid a number of unwanted issues with your heater & enjoy a continuous supply of hot water for your household’s needs.

Best of Luck!

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