First and foremost, when setting the temperature of your hot water heater you need to consider the safety for you and anyone that will use hot water in your home. By far the biggest safety factor to consider is injury from scalding or burns related to exposure to hot water. Water temperatures above 125°F (52°C) can cause severe burns instantly or death from scalds.
Children, elderly and disabled individuals are at the highest risk of being scalded. Households with these people may require a 120°F (49°C) or lower thermostat setting to prevent contact with water capable of injury. Always feel the water before bathing or showering. The chart below can act as a guide for determining the proper water temperature for your home.
|Temperature||Time to Produce a Serious Burn|
|120°F (49°C)||More than 5 minutes|
|125°F (52°C)||1.5 to 2 minutes|
|130°F (54°C)||About 30 seconds|
|135°F (57°C)||About 10 seconds|
|140°F (60°C)||Less than 5 seconds|
|145°F (63°C)||Less than 3 seconds|
|150°F (65°C)||About 1.5 seconds|
|155°F (68°C)||About 1 second|
To comply with safety regulations most manufacturers factory set the water heater temperature to 120°F (49°C). The US Department of Energy also recommends 120°F (49°C) as the optimal setting to balance safety and conservation.
Another important safety consideration is that in certain environments legionellae bacteria can build up in storage water tanks and plumbing, which can cause Legionnaire’s Disease or Pontiac Fever. If you or someone in your home has an immune compromised system or a chronic respiratory disease you should take additional precautions to make sure your plumbing system is providing you with safe water, which may require hotter temperatures and additional maintenance.