What Temperature Should a Hot Water Heater Be Set At?

A home inspector examines the water heating system for many possible defects, including water temperature excesses. Water heater temperature settings that are too high or too low can be hazardous.

Let’s first look at the problems caused by water temperature excesses.

Hazards of an overly-high setting:

Higher energy bills

The higher the temperature setting, the higher the energy consumption.

 

Danger of Scalds

The elderly and small children have thinner skin and burn more easily.  A baby can receive third-degree burns from 150-degree water in two seconds, and 140-degree water in five seconds.  Households with elderly or young children may be safest with the temperature set to 120 degrees.  As children age, the temperature can be increased if necessary.

Hazards of a too-low setting:

Disease

Water temperatures below 120 degrees can foster the growth of harmful bacteria, especially dangerous Legionella. Occupants with compromised immune systems or respiratory disease should set the temperature to 140 degrees.

Dishwashers should be using at least 140-degree water to properly disinfect.  Most modern dishwashers have built-in water pre-heaters to boost the water temperature if necessary, so you will probably not need to set your water heater to 140 degrees.  However, older dishwashers may not have a heater feature.

 

Annoyance / Inconvenience

Water that’s not hot enough leaving the water heater may not be comfortable when bathing or showering, because it cools on its way through the plumbing system.  Tank-type water heaters that are set too low will run out of available hot water faster as well.

 

How To Check and Set Your Water Heater Temperature

Electric Tank-Type

These heaters have one or two thermostats built into the heating element assembly. Here is a Link to a guide.

Gas Tank-Type

These heaters are easily adjusted using the adjustment knob usually located at the bottom of the heater.

Tankless

These are usually adjusted using a digital control on the unit or on a remote control.

You can check the temperature using a cooking or meat thermometer placed into a stream of running hot water.