How to Adjust a Hot Water Heater Safely
Is your hot water coming out too hot, not hot enough, or changing temperature throughout the day? Learning how to adjust a hot water heater can help improve comfort, reduce energy use, and prevent dangerously hot water from reaching your faucets.
The adjustment process depends on whether your home has an electric, gas, or tankless water heater. Although changing the temperature is often straightforward, homeowners should always follow basic safety precautions. Water heaters use high-voltage electricity, combustible gas, and extremely hot water, so an incorrect adjustment can create serious hazards.
This guide explains how to adjust your water heater temperature, what setting to use, and when to contact a licensed plumber.
What Temperature Should a Hot Water Heater Be Set At?
For most households, a water heater temperature of approximately 120 degrees Fahrenheit provides a good balance between comfort, safety, and energy efficiency.
A higher setting may:
- Increase the risk of scalding
- Raise monthly utility costs
- Cause faster mineral buildup inside the tank
- Place additional stress on plumbing fixtures
- Shorten the life of certain water heater components
Some households may require a slightly higher temperature because of their plumbing layout, appliance requirements, or unusually high hot water demand. However, increasing the temperature should be done carefully, especially in homes with children, older adults, or anyone with limited mobility.
Remember that the number shown on the thermostat may not perfectly match the water temperature at your faucet. Pipe length, cold water mixing, sediment buildup, and thermostat calibration can all affect the final temperature.
Before Adjusting Your Hot Water Heater
Before changing any settings, check the temperature of the water as it currently leaves the faucet.
Allow the hot water to run for several minutes. Fill a cup with the water and use a kitchen thermometer to measure its temperature. Testing the water before making an adjustment gives you a starting point and helps prevent unnecessary changes.
You should also determine which type of water heater you have:
- Electric tank water heater
- Gas tank water heater
- Tankless water heater
- Heat pump water heater
Each system has a different adjustment process.
Never remove access panels or touch electrical components while the water heater is receiving power. For gas models, do not attempt to disassemble the gas control valve or burner assembly.
How to Adjust an Electric Hot Water Heater
Electric water heaters usually have two heating elements: one near the top of the tank and another near the bottom. Each element normally has its own thermostat behind an access panel.
1. Turn Off the Electricity
Locate the water heater circuit breaker in your home’s electrical panel and switch it off.
Do not rely only on a wall switch. Water heaters generally operate on a 240-volt electrical circuit, which can cause severe injury. Confirm that the power is off before removing any access panels.
2. Locate the Thermostat Panels
Most electric water heaters have one or two rectangular access panels attached to the side of the tank. Remove the screws and carefully move the insulation aside.
You may also find a protective plastic cover over the thermostat. Remove or open the cover without touching any wiring.
3. Adjust the Thermostats
Use a flathead screwdriver to turn the thermostat dial slightly.
If the water is too cold, increase the setting by approximately 5 to 10 degrees. If the water is too hot, lower it by the same amount.
Both the upper and lower thermostats should generally be set to the same temperature. Different settings can cause uneven heating, inconsistent water temperature, or unnecessary strain on the system.
4. Replace the Covers and Insulation
Reinstall the plastic thermostat covers, insulation, and metal access panels. Make sure everything is returned to its original position before restoring power.
The insulation helps the tank retain heat and protects internal components.
5. Restore Power and Retest
Turn the circuit breaker back on. Allow the water heater several hours to reach the new temperature before testing the water again.
Avoid making several large adjustments at once. Small changes make it easier to find a comfortable and safe setting.
How to Adjust a Gas Hot Water Heater
Gas water heaters commonly have a temperature control dial on the gas valve near the bottom of the tank. The dial may display specific temperatures or general settings such as “Low,” “Hot,” “A,” “B,” and “C.”
1. Find the Gas Control Valve
Look near the bottom front of the water heater. The control assembly is usually connected to the gas supply line and includes a temperature dial.
Do not remove the valve or attempt to open the burner compartment unless you are trained to service gas appliances.
2. Turn the Temperature Dial
Move the dial slightly toward a warmer or cooler setting. Some manufacturers use letters instead of exact temperature numbers, so check the label on the water heater or the manufacturer’s instructions when available.
Make only a small adjustment at first. A minor movement of the dial may result in a noticeable temperature change.
3. Wait and Test the Water
Allow several hours for the tank to reach the new temperature. Test the water at a faucet using a thermometer before making another change.
If you smell gas at any point, do not adjust the unit. Leave the area and contact your gas utility or a qualified professional from a safe location.
How to Adjust a Tankless Hot Water Heater
Tankless water heaters usually provide the easiest temperature adjustments. Many units have a digital control panel located directly on the appliance or on a wall-mounted controller.
Use the up or down buttons to select the desired temperature. Some models require you to press a power, mode, or priority button before changing the setting.
Tankless systems may limit the maximum available temperature unless a professional changes an internal setting. These limits are designed to reduce the risk of scalding.
If the temperature display changes but your water remains too hot or too cold, the issue may involve:
- A dirty inlet filter
- Mineral buildup inside the heat exchanger
- A failing temperature sensor
- Insufficient gas supply
- Restricted water flow
- An improperly sized system
These problems require more than a basic temperature adjustment.
Why Is My Hot Water Still Not Hot Enough?
If adjusting the thermostat does not improve the water temperature, the thermostat may not be the real problem.
Common causes of insufficient hot water include:
Sediment Inside the Tank
Minerals in the water can settle at the bottom of a traditional water heater. A thick sediment layer makes it harder for the burner or heating element to transfer heat into the water.
Sediment can also cause popping, rumbling, or crackling sounds while the heater is operating.
A Failed Heating Element
Electric water heaters depend on upper and lower heating elements. If one element fails, the home may have a small amount of hot water that quickly turns cold.
A Malfunctioning Thermostat
A thermostat can become inaccurate or stop activating the heating system correctly. Increasing the setting will not solve the problem if the thermostat itself has failed.
A Damaged Dip Tube
The dip tube directs incoming cold water toward the bottom of the tank. If it breaks, cold water may mix with the heated water near the top, resulting in lukewarm water at the faucets.
An Undersized Water Heater
A water heater that is too small for the household may run out of hot water during showers, laundry, or periods of heavy use. Increasing the temperature is not always the best solution and can create a scalding hazard.
Excessive Hot Water Demand
Back-to-back showers, dishwashing, and laundry can temporarily use the tank’s available hot water. The system needs time to recover and heat another full tank.
Why Is My Hot Water Too Hot?
Water that is much hotter than the thermostat setting may indicate a malfunction rather than a simple adjustment issue.
Possible causes include:
- A thermostat stuck in the on position
- Incorrectly wired electric thermostats
- A failing gas control valve
- Different settings on the upper and lower thermostats
- A temperature sensor problem
- A defective mixing valve
Extremely hot water should be addressed promptly. Turn down the setting and arrange for an inspection if the temperature does not decrease.
How Long Does It Take for the Temperature to Change?
Traditional tank water heaters do not change temperature immediately. Depending on the tank size, incoming water temperature, fuel type, and condition of the system, it may take several hours for the adjustment to be noticeable.
Electric water heaters generally recover more slowly than comparable gas models. Tankless systems can usually reflect a new temperature setting much faster because they heat water as it is needed.
After adjusting a tank model, wait before testing the water. Testing too soon may measure water that was heated under the previous thermostat setting.
Can Turning Down the Water Heater Save Money?
Lowering an unnecessarily high temperature can reduce the amount of energy required to maintain the water inside the tank. It can also reduce standby heat loss, which occurs when stored heat escapes through the tank and connected pipes.
Additional ways to improve water heater efficiency include:
- Repairing dripping hot water faucets
- Insulating accessible hot water pipes
- Flushing sediment from the tank when appropriate
- Scheduling regular water heater maintenance
- Replacing an old or inefficient system
- Installing a properly sized water heater
- Using efficient plumbing fixtures
The best setting is not simply the lowest possible temperature. It should provide enough hot water for your household without creating comfort, sanitation, or safety concerns.
When Should You Call a Plumber?
A basic temperature adjustment may be appropriate when the water heater is operating normally and only needs a minor change. Contact a licensed plumber if you notice:
- Water leaking from the tank
- Rust-colored or cloudy hot water
- A burning smell
- Melted wires or damaged insulation
- A frequently tripping circuit breaker
- A gas odor
- Rumbling or banging noises
- Hot water that becomes cold unusually quickly
- Water that remains dangerously hot
- No improvement after adjusting the thermostat
- An error code on a tankless water heater
Do not continue increasing the thermostat to compensate for a failing component. Doing so can waste energy and create unsafe water temperatures without correcting the underlying problem.
Professional Water Heater Service in Spokane
Knowing how to adjust a hot water heater can help with minor temperature concerns, but persistent problems often indicate a failed thermostat, heating element, gas control valve, or another internal component.
JLR Plumbing provides professional water heater repair, installation, and replacement services for homeowners throughout Spokane and surrounding communities. We work with traditional tank water heaters, electric systems, gas models, and tankless water heaters.
Whether your hot water is too cold, dangerously hot, or running out faster than it should, JLR Plumbing can inspect the system and recommend the right solution.
Contact JLR Plumbing today to schedule professional water heater service in the Spokane area.
Frequently Asked Questions
What is the best setting for a hot water heater?
Approximately 120 degrees Fahrenheit is suitable for many households. The ideal setting may vary depending on the home, occupants, plumbing system, and hot water needs.
Do electric water heaters have two thermostats?
Most standard electric tank water heaters have an upper and lower thermostat. The two thermostats should typically be set to the same temperature.
Can I adjust my water heater without turning it off?
You should shut off electrical power before opening the access panels on an electric water heater. Gas water heaters often have an external control dial, but homeowners should not disassemble the gas valve or burner components.
Why does my hot water run out after one shower?
The water heater may be undersized, filled with sediment, recovering slowly, or operating with a failed heating element. High household demand can also use the available hot water faster than the system can replace it.
Why is my hot water hotter than the thermostat setting?
A defective thermostat, temperature sensor, gas control valve, or mixing valve can cause overheating. Have the system professionally inspected if the water remains excessively hot after lowering the setting.
How often should I check my water heater temperature?
Check it whenever the water suddenly feels hotter or colder than normal. It is also helpful to test the temperature after maintenance, a power interruption, or a thermostat adjustment.