The tankless water heater comes with a lot of convenience and ease of use, but it doesn’t mean that they are optimized to every customer’s needs. It is because they are made for commercial purposes, to address people’s requirements at large.
One of the basic adjustments that people are searching for is the tankless water heater temperature setting in 2022. So, we will be addressing this issue of how you can adjust the temperature setting in your tankless water heater.
Before that, if you want to increase the temperature of your tankless water heater because you feel that the water is not as hot as it once was, then it doesn’t necessarily mean that you should increase the temperature of your unit. So, the root cause must be found before you decide how you should proceed with it.
Finding Tankless water heater actual temperature
- Open the tap and let the waterfall until you get the hot water from the unit.
- Get a thermometer and place its measuring end under the hot water for 30-40 sec.
- Get the thermometer value and match it with the value shown on the tankless unit display panel.
- If both the reading is the same, your tankless water heater is working correctly, and you can adjust the temperature to your needs.
However, if the reading you measured does not match with the one shown on the unit, it means that your problem’s source is entirely different. At this time, you need to ask yourself, “when was the last time you had your tankless water heater flushed/cleaned?” If your answer was more than a year ago, then the source of your problem is likely to be hard water sediment that gets deposited on the heating element of your tankless water heater with time. This sediment or scalp is the accumulation of calcium or magnesium found in hard water (poor quality water) deposited on heating elements upon heating. Over time, the higher accumulation scalp makes it harder for the tankless water heater unit to heat the water efficiently and even reduce its lifespan.
Tankless Water Heater Temperature Adjustment
Being a tankless water heater owner, you probably know that Tankless water heaters come with the recommended setting of having the highest temperature of 120°, which is considered the best temperature to get a hot shower bath without scalding yourself. But as many people are looking for ways to increase the temperature to use the more sizzling water to clean their laundry of dirt, germs, and bed bugs, for which 140° is a better alternative.
Following the below instructions can help you in doing so.
1. Rheem Tankless Water Heater Temperature Setting
You need to know that recklessly increasing the temperature can result in scalding/burn. Take sufficient time to find the best temperature that matches your needs before you jump in the shower. Also, check to make sure nobody is in the shower when you do so.

Step-by-Step Guide
- Open the tap and let the waterfall until you get the hot water from the unit.

- Now, the gas and water shut-off valves must be closed.
- Press and hold the arrow pointing Up until it’s 120° changes to 140°.
- Keep on holding the Up Arrow and press the Down Arrow.
- Now, you can see that the temperature has gone to 140°. You can now adjust it between 120° to 140°.
- Open the gas and water shut-off valve.
- Suppose you want to reduce the temperature from a maximum of 140° to a maximum of 120°. You can do the opposite, as mentioned in the steps below.
- Press and hold the Down Arrow till it goes from 140° to 120°, and press the Up Arrow while holding the Down Arrow.
- You are back to a maximum of 120°.
The following steps also allow you to adjust the temperature to below 100°.
2. Novitz Tankless Water Heater Temperature Setting
- Just like any other tankless water heater, Novitz tankless water heaters also come with a LED display control that you can use to adjust the temperature.

- Use the Power button to turn off the remote control.
- Press and hold the flow alarm button until the temperature on the screen starts to flash.
- Use the Up and Down arrow to set the new maximum temperature and press the Power button.
- You have set the new maximum temperature successfully.
3. Rinnai Tankless Water heater Temperature Setting
Unlike the Rheem and novitz, you can’t adjust the temperature of the Rinnai tankless water heater using only the remote control screen. You need to access the inner section of the unit.
Step-by-Step Guide
- Keep the power of the Rinnai unit running as you can not do this in power off mode.
- Remove the safety clips on the unit by sliding them to the respective side.
- After removing the clips, you will see four screws underneath them.
- Unscrew the screws and remove the unit front cover.
- After removing the cover, locate the A button and press it once.

- Your LED screen will now show a “01A” reading.
- Press the on/off button once. The reading on the screen will change to “01b” or “016.”
- Press and hold the “A” until the screen returns to showing the temperature value.
- You can now increase the temperature to 140°.
This is how you can adjust the tankless water heater temperature setting.
Precautions to be taken before and after adjusting the temperature setting.
Make sure you let everyone in your house know about the temperature adjustment so they can also take precautions. Make sure nobody is in the shower or using water when you adjust the temperature.
The first thing you should do is to check whether the temperature you have set matches your need. To prevent this, don’t use your hand to check the temperature as the increased temperature can scald in seconds. It is better to use a thermometer to check the actual water temperature after the adjustment to ensure it is what you wanted.
Conclusion
Adjusting the temperature setting of your water heater is relatively easy and can be done by anyone. The key lies in knowing the trick. As depending on the brand and model, this trick can vary. You can always consult your owner manual for this; similarly, if you have a Rinnai, Rheem, or novitz tankless water heater, you can use the above steps to adjust the tankless water heater temperature setting. Always be careful and alert everyone before you do so to avoid any incident of scalding.
Frequently Asked Questions
How can I make my tankless water heater heat faster?
You do this by installing a recirculation pump. A recirculation pump circulates the hot water to the tap and will bring the cold water in your pipe back to your tankless water heater. This way, you get the hot water from the tap in the same instance as you have opened the tap.
Why does my tankless water heater go cold?
In plumbing language, it is called a sandwich. A sandwich refers to the alternating outflow of cold-hot-cold water. This happens because your tankless water heater is not getting a sufficient flow of cold water to kick start. This occurs when several taps are open, allowing most of the cold water to move there. The amount of cold water being supplied to the tankless water heater is insufficient to activate the flow sensor. Almost every tankless water heater comes with a flow sensor present near the cold water inlet. Only when the cold water flowing into the unit exceeds the minimum amount that the flow sensor can sense or activate does the tankless water heater kick start.
How to check whether a tankless water heater is heating the water properly?
You can use a domestic thermometer to check it. Bring the thermometer under the hot water and keep it there for 30-40 sec. Note the temperature value of the thermometer and compare it with the value shown on the tankless water heater display screen.
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