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: 

In addition, according to an article by the Regional Medical Center at Memphis, National Burn Awareness Week February 6 – 12, 2012 the tolerance for exposure of hot water to infants and seniors is shorter than that noted in Table 1 above,

Further analysis of the two tables reveals a conflict between what the experts believe is a “Safe for bathing” temperature and the warning that any temperature below 108℉ could cause exposure to the Legionella bacteria. So are we exposing persons to the danger of an illness when setting the temperature at or below the otherwise safe 104℉?  And, what is the “time for 3rd degree burn to occur” between 108℉ and 119℉?  It will likely be less than five minutes but the exact time data is not provided.

Some may argue, especially as it relates to small children, that children must be controlled by a supervising adult at the time the child is exposed to the normal bathing activity.  It is assumed that most parents, guardians, or other such supervising adults would know not to place a child in a tub filled with extremely hot water. They may not know the exact temperature but most adults can feel the difference between safe and not safe water temperature. On the other-hand children are known to slip away from the guardian eyes of an adult and could cause themselves harm because of their playful or inquisitive nature.

In conclusion, no matter which side you are on Plaintiff or Defense, the scalding of humans by hot water is definitely a concern and must be taken seriously. Children’s accidental burns are heartbreaking and emotions can cloud our vision. As experts, we need to rely on science and follow the evidence wherever it may take us.  While this article may lead you to believe that lowering the temperature of hot water is the only answer, reducing the temperature to a level where the temperature range can lead to unwanted and unhealthy bacteria growth is also not the answer. The only clear mechanical answer is to design and install a system appropriate for the use and location.

In the meantime, Safe Kids Worldwide ( and the American Burn Association ( suggest ways for adults to 

Prevent Scalds During Bath Time:

  1. Set water heater to a maximum temperature of 120 degrees Fahrenheit or just below the medium setting (presumably giving under five minutes of time to pull a child out of a too hot tub)
  2. Check bathwater temperature. Before placing the child in the bath, check the water temperature with your elbow (other sources) or the inside of the wrist as is done with heating baby’s milk. The water should feel warm to the touch, not hot.
  3. Place the child in the bath facing away from the faucet. This way they won’t be tempted to touch the hot faucet or turn on the hot water.
  4. Do not leave a child unattended.

A single article cannot answer all the questions about hot water its consequences.  Commercial, industrial, food industry, health care, and other such facilities vary greatly in the need and standards for each of those industries. Each must be examined for its unique need, use, and safety protocols.