Water Heater Temperature Settings: Safety, Efficiency, and Regulatory Considerations

Setting the correct water heater temperature is a crucial aspect of building design and maintenance, impacting both safety and energy efficiency. Setting the temperature too high can lead to scalding hazards and excessive energy consumption. Setting the temperature too low can promote bacteria growth and cause discomfort. For residential and commercial applications, regulations and best practices guide appropriate temperature settings.

Regulatory Requirements and Safety Considerations

Water heater temperature settings must comply with regulations that balance energy efficiency, safety, and public health. Local plumbing codes establish temperature requirements for various applications, including public restrooms and commercial facilities. Scalding injuries from hot water occur at temperatures above 120°F. At 140°F, water can cause burns in seconds. Tempered water is water that is typically maintained between 85°F and 110°F through the use of thermostatic mixing valves (TMVs). Public restrooms, hand-washing sinks in restaurants and schools, and public shower facilities in gyms and pools must provide tempered water to prevent scalding. OSHA mandates that emergency eyewash stations and safety showers provide tempered water between 60°F and 100°F to ensure safe use. Legionella bacteria cause Legionnaires' disease which is a type of pneumonia. Legionella can grow in warm, stagnant water in temperatures between 77°F and 113°F. To prevent the growth of Legionella bacteria in building water systems, ASHRAE Standard 188 recommends storing hot water at 140°F, with point-of-use tempering to prevent scalding. 

Recommended Temperature Settings for Water Heaters

Residential Water Heaters

For most households, the U.S. Department of Energy (DOE) recommends setting water heaters to 120°F (49°C). This temperature is sufficient to provide comfortable hot water while minimizing the risk of scalding and reducing energy costs. However, certain conditions may require adjustments:

• Households with Immunocompromised Individuals: Setting the water heater to 140°F (60°C) may be necessary to prevent bacterial growth (e.g., Legionella). In these cases, thermostatic mixing valves (TMVs) should be installed at points of use to prevent scalding.

• Large Families or Homes with High Hot Water Demand: A higher setting may be beneficial, but caution is needed to prevent burns. Additional energy costs also need to be considered.

• Certain household appliances like dishwashers may require a higher temperature setting for optimum cleaning.

Commercial Water Heaters

Commercial applications often require higher temperature settings to meet health and safety codes:

• Hotels, Restaurants, and Hospitals: Hot water is typically stored at 140°F (60°C) or higher to comply with sanitation requirements. Mixing valves are used to temper water to safe delivery temperatures.

• Industrial and Laboratory Facilities: Certain industrial applications require 160°F (71°C) or more, with appropriate safety measures in place.

• Healthcare and Assisted Living Facilities: Water temperatures should be carefully controlled to prevent scalding, often requiring thermostatic mixing valves to regulate output temperature.

Energy Efficiency and Cost Implications

Water heater temperature settings impact energy consumption and costs:

• Higher Temperatures = Higher Energy Costs: Every 10°F increase raises energy consumption by 3%–5%.

• Heat Loss and Standby Energy Use: Tank water heaters set at 140°F experience greater standby losses than those set at 120°F. 

Proper water heater temperature settings ensure compliance with health and building codes, minimizes energy costs, and protects users from scalding and bacterial risks. Understanding the role of equipment selection and sizing in public and workplace settings highlights the need for professional engineering consultation. By leveraging our expert knowledge, property owners and facility managers can ensure their water heating systems are safe, efficient, and fully compliant with all regulations. Contact us today to discuss your project.