The electric water heater thermostat in your Phoenix home is a relatively simple device. However, it can fail from time to time. Testing is the only way to determine if it has failed. After testing the thermostat, you may need to test other water heater elements if there are still issues with their water heater.

What Do Water Heater Thermostats Do, and Why Should Test Them?

There are typically two thermostats in your electric water heater. The upper thermostat is the primary control component. It’s what controls the upper and lower elements. In your water heater, your thermostat serves as a temperature-activated switch. When the water drops below a certain point, the thermostat senses the change, energizing one of the heating elements to heat the water.

Interestingly, the thermostat never actually comes into direct contact with the water. The back part of the thermostat registers the temperature of the outer layer of the tank. When you look at the thermostat, you’ll see it is held in place by a metal clip. The contact between the metal clip and the middle tank allows heat transfer from the water to the thermostat via conduction through the tank’s shell. Most of the tank is covered with insulation, except for the locations where the two thermostats are mounted.

Order of Operation

When you start using hot water in the morning, you pull hot water from the top of the tank. Water fills the bottom of the tank as the hot water is distributed throughout the home. The dip tube directs cold water to the tank’s bottom, which is first sensed by the lower thermostat. The lower thermostat signals the upper electric water heater thermostat. As long as the upper half of the tank remains hot, it energizes the lower element.

If you take a quick shower and use only a couple of gallons of water, the lower thermostat effectively maintains the water’s heat. However, for a longer shower or when multiple people need to shower consecutively, you can deplete the tank of available hot water. To counter this, the upper thermostat activates upon sensing the top half of the tank starting to cool off. This action preserves the hot water temperature before it reaches the person in the shower.


Your water heater contains safety devices to prevent electrocution, scalding from hot water, or tank explosions. The upper electric thermostat includes a high-temperature limit device. If the water exceeds 150°, this device shuts off both power elements. Water at 150° can cause skin burns. Regularly checking your water heater thermostat is crucial for safety to ensure it functions properly.

Reasons Why Your Water Heaters Thermostat Keeps Tripping

If your water heater thermostat trips one time, you can simply reset it. If your water heater thermostat is constantly tripping, it could be a sign that it’s going bad. A defective thermostat can cause the reset button to trip on its own. Your thermostat is what lets your water heater regulate the temperature according to the temperature you set. Until the thermostat is fixed, the heating elements will stay activated, overheating the water and causing the unit to trip repeatedly.

The best way to know if your thermostat is faulty is to have it inspected by a professional. You can quickly test whether your upper or lower thermostat is not working as it should. If you only get cold water when you turn on your shower, there is likely a problem with your upper thermostat. Or, if you get hot water for a few minutes but quickly become cold, the problem is likely with your lower thermostat.

Should You Replace a Water Heater With a Broken Thermostat?

There are several factors to consider in addition to the condition of the thermostat when determining if a water heater repair or replacement is due. One is the water heater’s age. Gas water heaters usually last ten years and tankless water heaters last 20 or more years. When your water heater approaches the end of its life, it’s often wiser to replace it rather than invest in costly repairs. Think of it like putting a new engine into an old car. It may not be the most economical choice.

If you’ve noticed an increase in your water heating bills and find yourself adjusting the shower dial more to maintain the desired temperature, this could indicate reduced energy efficiency in your water heater. As it becomes less efficient, it works longer and harder, resulting in higher energy bills. Water heaters account for about 14% of your energy bill, so any inefficiency should not be overlooked. If your water heater is aging and no longer providing hot water at the same level as before, replacing it might be a more cost-effective solution in the long run.

Consider the cost and frequency of repairs when making a decision. Utilize the 50% rule, which suggests that if a repair costs 50% or more of what a new water heater would, replacing it is the better choice. Also, factor in the frequency of recent repairs and the age of the water heater. Frequent breakdowns and an aging unit may indicate that further repairs are not worth the investment.

Benefits of a New Water Heater

If you realize that the issues with your water heater go well beyond the thermostat, and you’ve decided to invest in a new water heater, there are several benefits you can expect.

Energy Efficient

Newer hot water heaters are designed with improved efficiency features, such as better insulation and advanced heating mechanisms. This leads to potential cost savings on utility bills by reducing energy consumption compared to older, less efficient models.

Cost Savings

The enhanced energy efficiency of a new hot water heater translates into cost savings over time. You’ll see lower utility bills with reduced energy usage, contributing to long-term financial benefits.

Increased Water Capacity

If your current water heater struggles to meet the hot water demands of your household, upgrading to a larger-capacity unit can significantly improve performance. A new hot water heater with a higher capacity can accommodate larger families or households with increased hot water usage.

Safety Enhancements

Upgrading to a new hot water heater means accessing enhanced safety features. The latest models include innovative temperature and pressure controls, automatic shutoff mechanisms, and improved leak detection systems. These safety measures provide increased peace of mind and protect both you and your home.

Reliable Performance

A new hot water heater offers reliable and efficient performance. You can trust that it will function optimally, providing hot water when needed.

Your Trusted Source for Complete Plumbing and Appliance Solutions

At Wyman Plumbing & Mechanical, we have been successfully helping Phoenix, AZ, residents and commercial customers with their plumbing needs for many years. We keep our vehicles well-stocked and ready. Our vehicles are driven by our licensed plumbing company team. Whether you are looking for basic repairs or complex installations, we are here to help. Our services include general plumbing, tankless water heater installation, water treatment service, water softeners, and gas line installation. We offer drain repair, camera inspection, smoke testing, and appliance repair.

Contact Wyman Plumbing & Mechanical today and see for yourself what sets us apart from the rest.

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