Hot Water Scalding

May 18, 2020 in Hazard, Injury, Safety, Temperature

Perhaps one of the least analyzed areas of personal injury has to do with the causes of burns due to scalding by hot water. The temperatures which lead to burns differ between age groups and the ways to control those temperatures are often overly generalized.

For instance, in the International Plumbing Code (IPC) (2018 IPC 412.10) for the shower, hot tub, and head shampoo sink faucets water temperature is specified to not exceed 120℉ (2018 IPC 412.3 & 412.5). Anything above that temperature is considered to be a hazard. However, the code is incomplete because it is silent as to how long can or should, a person exposes themselves to a temperature of 120℉.  Anyone who has spent any time in a hot tub knows that your body is somewhat comfortable in temperatures in the ’90s but once you extend into the 100’s your duration in that hot tub diminishes with each degree rise in temperature.

We also need to understand that going too far below the 120℉ temperature could expose us to the dangerous Legionella bacteria well known to cause Legionnaires’ disease. According to the Centers for Disease Control and Prevention (CDC) (, this bacteria occurs naturally in a variety of freshwater bodies such as lakes, rivers, and streams where the bacteria are in relatively low amounts and not likely to cause a health hazard. The same cannot be said for the bacteria residing in the plumbing systems of either residential or commercial buildings. Legionella bacteria thrive in such systems with temperatures between 77℉ – 108℉. It is therefore imperative that our hot water storage and delivery systems control the temperatures above or below that range of temperature but as of this writing, they do not.

Some may ask if the hot water temperature can be controlled with the thermostat setting found on the hot water tank or today’s tankless water heaters.  The short answer is only to the degree of its maximum heat and therefore should not be relied upon for safety settings.  IPC 501.6 requires that “the temperature of water from tankless water heaters shall be not greater than 140℉ were intended for domestic uses”.  That leaves a 20-degree difference between the required maximum and the heating capacity of the water heater. Furthermore, standard water heaters do not have a set of maximum water temperature. In fact, in some states such as California, the plumbing code is clear that “The water heater thermostat shall not be considered a suitable control for meeting this provision” (provision meaning controlling the temperature coming out of the spigot at a maximum of 120℉) (2016 California Plumbing Code[CPC] 407.3). The mechanics of controlling the temperature beyond the water heater thermostat is a discussion we will tackle in a follow-up article. For now, we can say that a simple handheld thermometer is a simple first step by property owners and tenants to check the delivery temperature of the water.

Currently, the codes are silent on the temperature delivery for hot water at a sink or lavatory in a private building such as a house or apartment. They only mention a maximum 120℉ range is for “Public Lavatories” (2016 CPC 407.3).  Those would logically include places such as hospitals, restaurants, airports, gas stations, and other places where the “public” has access to lavatories. What about domestic and commercial kitchen sinks? As of the date of this article, the plumbing code is silent.

So we see what the plumbing codes say but in this author’s opinion that is not sufficient to prevent scalding or to truly understand what the consequences are when deciding how to approach burn associated cases involving hot water.

According to the American Burn Association – Scald Injury Prevention – Educator’s Guide:

Young children have thinner skin resulting in deeper burns than adults for the same temperature and exposure time to a scalding substance. The proportion of a child’s body that is exposed to any given amount of a scalding substance is also greater: the same cup of spilled coffee will burn a much larger percentage of a small child’s body. Small children also have little control of their environment, less perception of danger, and less ability to escape a burning situation on their own. Children grow fast and can reach new, dangerous things every day. They do not realize that hot liquids burn like fire. 

The Guide provides the following basic table for how hot temperature can affect a human being: