Maintenance Thermostat

How to test electric water heater thermostat with digital multimeter

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A faulty water heater thermostat is an inconvenience to you, your family, or your business. Although there are different types of failures, a malfunctioning electrical system is a common problem. The point of failure may vary and could be faulty wiring or loose connections, a bad heating element, or a water heater thermostat.

A failure in the thermostat, heating element, or both could lead to completely cold water. Or partly warm water that does not reach the set temperature.

If your water heater stops providing you with hot water according to your settings and requirements, you can test the element and thermostat to ensure they are functioning properly. 

Thermostat role in water heaters

The main work of a thermostat in a heater is to regulate and maintain the water temperature, hence ensure safety and optimize energy use. When it starts malfunctioning, it cannot control the water temperature to suit your requirements. 

In practice, the thermostat controls the heating elements to maintain the water at the set temperature. When the water is cold, the thermostat automatically powers the elements to heat the water to the desired temperature. Upon reaching the set temperature, the thermostat shuts off the element, until the water gets colder again. As such, its work is to ensure the water temperature remains constant at a certain set level. Consequently, it reduces the risks of heating the water to very high and unnecessary temperatures, hence reducing the energy use without compromising comfort.

water heater thermostat

Types of water heater thermostat failures and impact

A faulty thermostat may not provide any control, or may only function partially and could result in your water not reaching the usual hotness levels.

Potential faults include;

  • A completely open thermostat that does not power the element at all.
  • A partial open thermostat – heats the water partially such that the temperature does not reach the desired level.
  • A short circuit- In this case, the thermostat does not provide any control and will continuously heat the water. Most often, a shorted thermostat results in the tripping of the heater reset button or high limit switch. 

Most standard water heaters have two thermostats, an upper one and a lower one. If one of these fails, it impacts the water heating process differently. For example, when the upper thermostat goes bad, you will notice that cold water will run out of the heater when you turn on the hot water tap. On the other hand, with a faulty lower thermostat, the water is initially hot, but it becomes cold after some time.

How to test the thermostat with a digital multimeter

Once you suspect that a thermostat is faulty, it is best practice to test and confirm that it requires a replacement.

Before testing the thermostat, confirm that the heating element is in working condition. Otherwise, an open-circuited heating element or one with a short circuit to the ground will result in some misleading measurements.

Please check here on how to test a heating element with a multimeter.

Unless physically broken, the common problems with the thermostats are due to failure in electrical continuity, which usually gets faulty due to wear and tear, unstable or poor quality power, etc. To identify the problem, you can use an analog or digital multimeter to test for continuity. 

Tools for testing water heater thermostat

Although the tools may vary according to the model, below is the list of the items you require.

  • A flat screwdriver 
  • Philips screwdriver
  • Nut driver 
  • Digital multimeter
  • Non-contact voltage tester
  • Basic technical skills

Let us now look at the steps you need to test the thermostat with a multimeter.

Step 1: Disconnect electrical supply to the heater

For safety reasons and accurate measurements, disconnect the power from the electrical panel. You can do this by turning off the breaker. To confirm that there is no power; use a meter or non-contact voltage tester at the terminals

Step 2: Remove the water heater’s access panels

Use a flat screwdriver or nut driver to remove the lower and upper thermostat access covers. Roll the insulation that covers the thermostat back and also remove the internal plastic covers. You can tape the insulating material in a place and put it out of the way as you work on the thermostat.

Step 3: Confirm that there is no power to the water heater

To avoid short circuits or electric shocks, ensure that the electrical supply is off. You can use a digital meter to measure the voltage across the thermostat terminals, which should give zero volts if off. Alternatively, use a non-contact voltage tester to confirm. 

Step 4: Confirm Reset button has not tripped

The reset button may trip when there is a problem with eth thermostat. For example, it may trip the reset switch if the thermostat has short-circuited contacts or out of calibration. Also, the reset button may trip due to a faulty heating element. 

Step 5: Disconnect the thermostat wiring

Before removing the cables, draw the wiring diagram to avoid making mistakes when reconnecting. Alternatively, take a picture using a camera or even a mobile phone. 

To physically remove the wires, use the Phillips #2 screwdriver to loosen the screw and pull each cable out. Repeat this for each of the terminals.

Step 6: Check the thermostat continuity with a digital meter

Set the digital multimeter to the lowest resistance range. Most meters have a typical low range of 200ohms and may include a tone.

Place one of the meter probes on the screw terminal on the left side of the thermostat. Place the second probe on the other terminal, still on the left side. The digital meter should display a low resistance reading, hence confirming continuity. If the meter reading is very high or open, the thermostat is faulty and will require a replacement. 

Testing water heater thermostat

Repeat the test on the terminals on the right side and also for the other thermostat.

If the thermostats are functional and the water heater still does not function properly, test the wiring and heating elements. 

Please see our guide on how to test a heating element with a digital meter.


An electric water heater uses a thermostat to maintain the water temperature at the desired level. A failure in the thermostat makes it hard to control the heating elements and the water temperature. 

Most often, the water does not get hot as per the set temperature. Fortunately, you can test a thermostat with only a few tools and basic skills. However, you need to be careful and ensure that you have disconnected the electrical power before checking the thermostat for continuity. Once you identify a faulty device, remove and replace it with a similar model.

Maintenance Thermostat

Busted Water Heater

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A busted water heater leads to disruptions inconveniences, and sometimes, safety risks, and costly repairs. Despite the many benefits water heaters offer homeowners and businesses, a malfunction is likely to occur once in a while. And when this happens, you might not get your favorite hot temperature. In extreme cases, a faulty water heater may pose safety and financial risks to yourself, your family, and your property.

Generally, typical water heaters have a limited service life of about 8 to 10 years. Although regular maintenance enables you to get the best out of your investment, the water heater will eventually reach the end of its service life. At this time, you start experiencing regular leaks and other problems due to rust, tear and wear, corrosion, scale buildup, and other unavoidable failures that result from aging. 

Most of these issues compromise the integrity of the water heater hence increasing the risks of failure. In most cases, there are always signs of an impending water heater bust. 

Warning signs of a potential water heater bust 

Water heaters with metal storage tanks are the most vulnerable to failure. For example, there are risks of water leaking from the seams or loose fittings and even explosions due to rust, excess pressure, and temperature. 

This image has an empty alt attribute; its file name is old-water-heater.jpg
Old water heater Image The Blue Book

Some of the warning signs of an impending water tank bust include;

  • You have an aging water heater that is more than ten years old.
  • The water heater makes some unusual sounds, such as rumbling noises, popping, clanking, or banging as it heats up. Most often, this happens due to sediment build-up in the tank.
  • Heater produces brownish or yellowish-colored water with unusual odors. With time, water heaters accumulate minerals and from the water, and debris from corroding or rusting metallic parts.
  • Visible rust on the tank exterior, especially at the seams and around the pipe fittings.
  • Water does not heat to the temperature setting level
  • A leaking water heater due to a weak tank structure, broken seam, a crack, or a faulty T&P valve is another sign of an impending problem.

Most leaks are not always serious to cause the water heaters to completely malfunction, but you need to fix them. Some of the problems are easy to repair, while others require a plumber. 

What causes busted water heaters?

Although a busted water heater is probably not one of your top concerns, it is a common occurrence that you should prepare for. Generally, there is always the risk of rupturing, and this comes about due to aging, maintenance, structural, and operations issues. Among the most common causes of busting water heaters include;


With time, the metal that makes the water heater tanks will suffer from corrosion. The rusting weakens the affected parts that may give way when they are unable to withstand the pressure. Although some heaters have sacrificial anode rods to prevent or reduce corrosion on the critical parts, these deteriorate with time. A worn-out rod provides less protection hence resulting in corroded and weak tank walls.

A brown tint on your heater tank’s internal walls is a sign of rust that requires addressing. One way of addressing this is to check for and replace a worn-out anode rod. Additionally, monitor the exteriors for the water tank and address any corrosion issues. If you notice small leakages from the tanks, have a plumber check it because this could be a sign of pinholes and a weakened tank structure with the potential to leak significantly.

Excess internal pressure

An excessive pressure builds up inside the tank results in rupturing, especially at high temperatures. Although heaters have pressure and temperature relief valves, these are prone to failure wear and tear. A malfunctioning valve will start leaking or opening more frequently. The lack of proper control has the potential to cause serious pressure problems and busting. The risk increases at higher temperatures since this is when the pressure builds up faster. A much safer temperature to overcome this problem is between 120 and 125 degrees F.

Sediment or scale build-up

Hard water contains various minerals that, over time, will settle at the bottom of the heater tank. As time goes, a significant amount of sediment will settle at the bottom and around the heating element or burner, hence insulating it and prevent direct contact with water. As this happens, the elements cannot heat the water to the desired temperature using the normal settings and time, and will, therefore, work harder to achieve desired results.  

Eventually, this will mean overheating and accelerating the deterioration of the tank material. Some of the signs of sediment build-up include a knocking or popping sound from your water heater.

What to do when you have a busted water heater

A busted water heater presents several risks and, therefore, dangerous. Although you may not fix it by yourself, there are a few things you can do to reduce the risks and further damage, as you wait for professional help. 

  • Shut off the electrical power or gas line and water supply to the tank. If the leakage is extensive, consider powering off the entire electrical system to prevent the risk of shocks from water in contact with live conductors.
  • Take the photographs of the busted water tank, the damage, and the entire leak for investigation and insurance purposes.
  • Clean up the area, preferably starting with a wet vacuum cleaner to remove as much water as possible. Afterward, you may consider using a dehumidifier to dry out the areas at risk of growing molds due to dampness. 
  • Call a plumber or a professional with experience handling such failures. If you are not comfortable cleaning up, call the plumber after switching off the power and water. Additionally, you may report the bust to your insurance for compensation.

What to do when you have leakages

Because of the potential risks and damage a busted water tank presents, there are a few things you can do to prevent this from happening. In particular, the following are the steps to take when you notice leakage. In most cases, it is better to engage a plumber in some of these tasks. However, before you call the plumber, here are the things you can do to minimize the risks.

Busted water heater leaking
Busted water heater -leaking

Since the leaks are the signs of an impending failure, here is how to respond.

Shutdown the water supply

Stop the flow of water into the tank by turning the shutoff valve clockwise. If your system uses the lever control, turn it to the close position. In case you do not locate the shutoff valve or other means to stop the water, close the main supply to the house.

Turn off the electrical or gas supply to the heater 

Shut off the electrical power by switching off the circuit breaker at the service panel. For gas-powered systems, turn off the gas line the goes into the system. Failure to disconnect electrical power to the systems means that the heating elements will remain hot – increasing the risk of damage or fire.  

Locate the water leak

Check your water heater and identify where there is a leak. Potential areas include the seams, water inlet pipe or fitting at the top of the tank, a broken temperature and pressure (T&P) valve, drain valve, etc. In particular, look for areas that show signs of corrosion or rust. 

Fix the leakage

Depending on the location and type of leakage, take the necessary measures to fix the problem. The repair could be a simple task such as replacing a faulty T&P valve, tightening loose fittings using a pipe wrench, and more. However, it could also be a complex repair job that requires a plumber. If you cannot figure out where the problem is or do not have the necessary skills or tools to fix the leakage, consider engaging a professional plumber. 


Water heaters require regular cleaning and maintenance to ensure safe and reliable operations. However, even after doing this, problems may occur due to a variety of reasons. In particular, aging, corrosion, sediment build-up, and excessive pressure are major problems that lead to leaking water tanks and water heaters failures.

To reduce safety and financial risks associated with a busted water heater, ensure that you regularly check the system while addressing any issues. For problems that you cannot fix, shut off the power, gas, and water supply to the heater, and then call an experienced plumber.

Maintenance Tankless Water Heaters Thermostat

How to Test Heating Elements with a Multimeter

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Electric water heaters provide convenience and comfort around the house and other environments where they provide hot water for showering, dishwashing, and other applications. Today, more and more households are installing the systems due to the safety, low upfront, and maintenance costs. However, as it happens with many electrical systems, the heaters may fail due to various reasons. 

In most cases, a malfunctioning heating element, electrical system, or thermostat leads to the inability to heat water to the desired temperature. In particular, if one or more heating elements are faulty, you will notice that your water does not get hot as per the settings.

Electric water heating elements

The main work of the heating element is to convert electrical energy into heat. When electricity passes through, it will heat the surrounding water before it goes to the shower or another application area. 

Unfortunately, the electrical heating elements have limited lifespans. Most often, several conditions accelerate the deterioration hence reducing their service life. Some of the problems include mineral deposits in the water, air pockets, power surges, loose connections, faulty thermostats, and more. 

Common problems with the heating elements include burning up and breaking the continuity or short-circuiting and causing the heater to trip the circuit breaker or blow up the fuse. Also, the element material may deteriorate and increase the electrical resistance, resulting in the inability to heat the water to the set temperature.

Luckily, the elements are like consumables and, therefore, easily replaceable. That said, you need to test and ensure that the part is faulty before ordering a replacement. 

Rheem electric water heating element Image – Rheem

You have the option of calling a plumber or electrician when you cannot get hot water. However, before calling them or before ordering a replacement, you can do a few tests to determine if the elements are faulty. To do this, you need some basic technical skills and the following tools

  • Screwdriver
  • Non-contact voltage detector
  • Multimeter
  • Safety goggles
  • Gloves

Step by step testing of electric water heater elements

In practice, the elements are usually inside the water heater system. As such, it is not possible to inspect them visually. Moreover, the actual heating element has a metallic enclosure, so you cannot determine if it is working or faulty using your eyes unless it has severe physical damage. The best and effective way to test it is by checking the electrical continuity using a millimeter. Because of the voltages involved and the risks of fire and electric shocks, you need to follow various safety precautions. A typical step by step testing of a heating element is as below;

  1. Disconnect the power before working on the electric water heater. To do this, locate the water heater circuit breaker at the service panel and switch it off. If not sure about the specific breaker, turn off the entire electrical supply, assuming it will not affect other critical areas. Alternatively, use a multimeter or non-contact voltage tester to ensure there is no power at the supply input terminals.  
  • Drain the hot water in the heater. Open the hot water faucet while allowing the cold water to flow inside. Ideally, test the unit with lukewarm and not hot water. The process depends on the type of water heater and may not be necessary for some models. 
  • Locate and remove the access panel that covers the heating element. Note down the wiring to the element contacts and, if possible, draw the diagram. Loosen the screws and remove the wires from the element’s electrical contact terminals.  
electric water heating element connections
  • Check the wattage and voltage of the element. The information is usually on the nameplate or base of the heating element. To determine the electrical resistance value of the element, divide the square of the voltage by the power (watts) rating. 

            That is R= VxV /P or V2/P.  


R is the resistance

V the voltage rating

P the power rating in watts

Supposing the wattage is (P) is 3000W and voltage (V) is 240v, the resistance will be 240×240/3000 = 19.2 ohms. A good element should therefore have resistance around 20 ohms.

  • Set your millimeter to the resistance measurement and appropriate range, preferably the lowest where the calculated or expected value falls within. Please note that even if you cannot read the rating, the resistance is usually in tens of ohms and mostly less than 100 ohms.
  • Place one of the meter probes on the terminal where you have removed the wire. Put the other probe on the remaining terminal and read the result on the dial or display. If the element is functional, the reading will be closer to the figure you calculated in (4) above. Even when you have not calculated the resistance, most will read between 10 and 30 ohms.

A significant deviation indicates a faulty heating element, hence the need for a replacement. For example, a zero reading indicates a short circuit and will burn the fuse or trip the breaker. On the other hand, an infinite or very high reading (over 1000 ohms) indicates an open circuit, – which is the most common problem.

  • You will also need to test if the element is short-circuiting to the ground. To do this, place the probe on one of the contacts on the heating element. Take the second probe and touch its metal base, a metallic or grounded part of the heater system. Repeat this with the other contact. If you notice a low resistance, know that there could be leakage, and you need to replace the element.

When testing for current leakage, it is best practice to disconnect the two wires supplying the heating element.

Precautions when testing heating element

To prevent electric shocks, burns, or fires, switch off the power at the service panel before opening the unit. 

If you find a faulty element, ensure that the replacement part has exact physical dimensions and rating in terms of voltage and wattage as the broken one. For example, if you have a 120 volts element, never replace it with 240 volts even if they have the same wattage. The best practice is to take the faulty part with you so that the suppliers can give you a replacement that matches yours.

Before disconnecting the heating element, thermostat, or any other electrical component, note down or draw the wiring diagram to refer to when installing the new part. 


The electric water heater is an essential system in the house. It enhances the quality of life and comfort. However, the unit comprises various components that deteriorate or fail with time. One of the most common malfunctions is the inability to heat water to the right temperate, and it happens when one or more elements have failed. 

Luckily, with some basic technical skills and tools, you can test, identify and replace a faulty electric heating element. To do the test, disconnect the power and open the cover to access the element’s terminals. Remove the wires and use the multimeter to measure the resistance between the two terminals of the element. The electrical resistance is usually in tens of ohms, and if zero, very high, or infinite, the heating element is faulty and will require a replacement.

Tankless Water Heaters Thermostat

Tankless Water Heater Temperature

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A tankless water heater provides many benefits over the traditional storage-based system. Instead of heating water in advance and then store it for later use, the instant system only heats the water on demand. Besides costs and energy savings, tankless water heaters are easy to install and maintain. Although they provide energy and water savings, you can optimize the temperature to improve safety and reduce your bills further. In particular, lowering the temperature will save energy and reduce water usage without sacrificing comfort.

Why change the water heater temperature

While you may need certain temperatures for some applications, the heat may be inadequate or uncomfortable for others. Usually, tankless water heaters have a default temperature setting of 140 degrees Fahrenheit. However, this may be too hot for some users and especially the children and elderly. Even for young and middle-aged people, the hot water may burn or scald them.

Tankless water heater LED panel – Image Ecotouch

Usually, the safe and comfortable temperature is 120 o F or 50 o C but you can still set it to a lower value depending on your preference. Some heaters incorporate anti-scald devices or thermostatic mix valves that regulate the temperatures and ensure that it reaches the point of use, such as the showerhead or sink at a constant and safe 120 o F or 50 o C. However, these will only improve safety but do not provide much energy savings since they will cool the water near the outlet.

When a unit serves many applications such as showering, dishwashing, laundry, and more, you may need to install it in the most appropriate place and then run pipes to the application area. As the water flows through the piping, it will lose some heat to the surrounding and reach the sink or showerhead at a lower temperature. 

In particular, using uninsulated metal pipes over long distances will lead to significant losses. In such cases, you may consider adjusting to a higher temperature to compensate for the losses. However, this will result in more energy use and bills.

That said, although you have the liberty to set your temperature at the maximum figure, you may need to consider other issues such as safety, especially if other people are using the same shower or water to do dishes and other activities. You also need to note that the higher the temperature, the higher the energy you require for heating your water.

Advantages of low-temperature settings on a tankless water heater

Benefits of adjusting the temperature of a tankless water heater include improving safety by preventing scalds and burns and reducing your energy and water bills. 

Saving energy

If you set your temperature too high, you will require more energy to heat the water. And this means higher energy bills at the end of the month. In a typical setting, reducing the temperatures by 10 degrees results in 5% energy bill savings, and you can realize 10% savings if you reduce by 20 degrees. However, this may vary depending on the heater model and efficiency. Besides the savings, using less energy reduces environmental degradation.

Improved safety 

The default temperature setting for a new tankless water heater is usually 140 o F or 60 o C. Generally, showering with such hot water can burn or scald you seriously. In particular, the temperature is too high for the elderly since they may take time to sense the excess heat. Similarly, children are at risk due to their delicate skins. In either case, the hot water may lead to scalding or burns. 

Saving water

If you heat to higher and dangerous or uncomfortable temperatures, you need to mix with more cold water to make it comfortable and reduce the risk of burns. As such, you end up using more water, unlike if you had just heated it to a lower and more comfortable temperature.

Checking your hot water temperature

If you do not know your current water temperature setting of the tankless water heater, check the LCD, if any, or at the dial position for some models. Alternatively, use a thermometer to manually check the water temperature at the outlet of the shower, sink, or other application areas. First, turn on the water heater, let it run for a few minutes, and then take the reading.

While you can rely on the tankless water heater thermostat to maintain the temperature at your desired value, you can check it manually at the outlet. Losses and other factors may cause temperature changes between the heater and point of use. You should then adjust the settings to compensate for the losses and ensure that you achieve the desired output that is comfortable and cost-effective.

How to adjust the tankless electric water heater temperature

Most tankless water heaters provide a flexible temperature range to suit different applications and preferences. For example, if you want to shower with scalding hot water, you can set your temperature at the maximum setting, which is about 140 o or 150 o F for most units. However, for most people, a 120 o F or 50 o C setting provides a comfortable and safe temperature for showering. 

In practice, tankless water heating systems have adjustable temperature settings. However, the accuracy and method of adjusting may vary from one model to the other. As such, you need to establish your system and how to change the settings, usually available from the user’s manual.

For tankless water heaters with an LED panel and control, adjust the temperature while checking the water to ensure that you get the right setting. For some models, you may need to use dial control. Once you set a temperature, an inbuilt thermostat monitors the water as it gets hot. Upon reaching the set temperature, the thermostat cuts off the power to the heating element. It then continues monitoring the water and powering the heating element, on and off, to maintain the water at the set temperature.

Adjusting temperature on tankless water heater -Image:Noritz

As mentioned earlier, you may consider using a thermometer to ensure that your water is at the right temperature at the point of use. Alternatively, feel the water on your skin and, if possible, ask all the other users to check so that you can adjust the temperature to a safe setting for everyone.

In a home where one tankless electric water heater serves multiple applications such as dishwashing, laundry, and shower, you will set the temperature once. However, if you have different tankless heaters around the house, each for its specific application, you need to adjust the temperature individually to suit the application.

Thermostatic mixing valve

Another approach to ensure that the water reaches the shower or other application area at the desired temperature is to use a thermostatic mixing valve. It automatically mixes the right amount of hot and cold water to provide the set temperature while responding to fluctuation in the pressure or other factors. The add-on device, installed near the hot water outlet, controls temperature hence improving safety and comfort.

Remote temperature control

With most modern tankless water heaters, you can add digital technologies that would allow you to control them remotely. For these models, you can connect them to the internet using Wi-Fi or other communication technologies. Adding connectivity enables you to adjust the water temperature using your phone or tablet. It also gives you the ability to monitor the usage of hot water, electricity, or gas remotely. For example, the solution allows you to turn off your heater remotely from anywhere, even when you are not at home.

Temperature control via smart phone – Image: Noritz

All you need is to purchase and install the wireless digital control kit. However, this will also require an internet connection to enable you to control the heater remotely from your tablet, smartphone, or other connected devices. 


Although a tankless comes with a considerable temperature range, the default setting of 140o F may be too hot and uncomfortable for most users. At this temperature, there are high risks of burns and especially for children and the elderly. As such, you should consider using a lower setting. In most cases, a temperature of 120 o F is safe and comfortable for everyone, not forgetting that it helps you save on energy and water bills and the environment.

Luckily, most of the tankless water heaters in the market provide an easy control system that allows you to adjust ot customize the water temperature according to your needs. 

Tankless Water Heaters Thermostat

How to test water heater element

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Watch the video below to see how you can test a hot water heater element.


  1. How to test water heater element.
  2. How to test water heater element.
  3. How to test a water heater element with a multimeter.