How to Check and Adjust Your Water Heater Temperature — New Mexico
Complete checklist with climate-adjusted recommendations for New Mexico
Overview
Setting your water heater to 120 degrees F provides the optimal balance of scald prevention, energy savings, and bacteria control. Temperatures above 120 degrees waste energy and pose a scald risk, especially for children and elderly household members. Temperatures below 120 degrees allow Legionella bacteria to thrive.
Step-by-Step Guide
Locate the temperature dial
On gas water heaters, the temperature dial is on the gas control valve near the bottom front of the tank. On electric water heaters, there are usually two thermostats behind access panels on the side of the tank (upper and lower).
Read the current setting
Most gas water heater dials show relative settings like WARM, HOT, and VERY HOT rather than exact degrees. The 'HOT' setting on most manufacturers corresponds roughly to 120 degrees F. Electric thermostats typically have degree markings.
Test the actual water temperature
Run hot water from the faucet closest to the water heater for 2-3 minutes until fully hot. Fill a glass and measure with a cooking or candy thermometer. This gives you the actual delivery temperature, which may differ from the dial setting.
Adjust the gas water heater dial
If the temperature is not at 120 degrees F, turn the gas control dial. Most dials have small notches between labeled positions. Each notch typically represents about 10 degrees. Mark the original position before adjusting.
Adjust electric water heater thermostats
Turn off the breaker to the water heater. Remove the upper and lower access panels. Pull back the insulation to expose the thermostat. Use a flathead screwdriver to adjust the setting to 120 degrees F. Both thermostats should be set to the same temperature. Replace insulation and panels, then restore power.
Wait and re-test
Allow 2-3 hours for the water heater to stabilize at the new setting. Then re-test the water temperature at the same faucet. Adjust further if needed. Repeat until you reach 120 degrees F.
What You'll Need
Tools
- - Cooking or candy thermometer
- - Flathead screwdriver (for electric water heaters)
- - Drinking glass or cup
Cost Estimates
DIY Cost
$0 - $10 (thermometer only)
Professional Cost
$75 - $200 for thermostat diagnosis and adjustment; $200 - $400 for mixing valve installation
Safety Tips
- Always turn off the breaker before opening electric water heater access panels. There is high-voltage wiring inside.
- Water at 140 degrees F can cause a full-thickness burn in 5 seconds. At 120 degrees F, it takes 5 minutes. The difference in safety is enormous.
- If anyone in the household is immunocompromised, consult a doctor about water temperature. They may recommend 140 degrees F with anti-scald mixing valves at faucets.
- Do not set the temperature below 120 degrees F, as this allows Legionella and other harmful bacteria to grow in the tank.
When to Call a Professional
Call a plumber if you cannot locate the thermostat, if adjusting the dial does not change the water temperature, if the water is too hot even at the lowest setting (which may indicate a stuck thermostat), or if you want to install a thermostatic mixing valve for precise temperature control.
Pro Tip
Lowering your water heater from 140 degrees F to 120 degrees F can save 6-10 percent on your water heating costs. For a household spending $400/year on water heating, that is $24-$40 in annual savings with zero loss of comfort.
Common Mistakes to Avoid
- Setting the temperature too low (below 120 degrees F) to save energy. This creates a health risk from bacterial growth.
- Adjusting only one thermostat on an electric water heater. Both upper and lower must match, or you get inconsistent temperature.
- Not testing the actual water temperature with a thermometer and relying solely on the dial markings, which are often inaccurate.
- Forgetting to turn off the breaker before opening electric water heater access panels.
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