Hot water is important for our every day lives. It helps us bathe and wash clothes, clean dishes and countertops, and even comforts and soothes us after a hectic day at the office. But extremely hot water can also be dangerous! How dangerous depends on how high the temperature. While hot water temperature is a personal preference, homeowners should be aware that temperatures in excess of 120° F can present a safety hazard due to the risk of scalding.
Storage type water heaters have been used in domestic applications since the early 1900s. Since this time, water heater technology has continued to improve, and is a reliable source of hot water in almost every home. However, as a large water storage device, there are limits to the regulation of precise temperature control. Water heaters alone cannot accurately control the hot water temperature at the point-of-use. Since the water heater thermostatic control is typically located at the bottom of the water heater, it does not sense the water temperature at the upper outlet of the water heater. Without further temperature control downstream of the water heater, there is potential to experience hot water scald hazards at the point of use.
Simple huh? Just turn the thermostat back and problem solved! Well… not so fast…
Setting the water heater thermostat at the 120° F setting is typically recommended. However, it is common for the household to experience multiple intermittent short draws of hot water usage, whereby cold water gets introduced to the bottom of the water heater causing the thermostat to sense the cold water, which then turns the burner on. When this intermittent usage occurs within a relatively short time period, it causes overheating of the water accumulated at the top of the water heater. This is referred to as thermal stacking or stratification which can result in hot water temperatures in excess of 140° F at the top of tank. Water at an extreme scalding temperature such as this may instantly cause irreversible third-degree burn injuries.
On the flip side, water that is not “hot enough” can present a potential and verifiable health hazard such as Legionnaires Disease. Legionella pneumophilia bacteria is the agent of Legionellosis, or Legionnaires Disease. Legionella bacteria are commonly found in potable water supplies such as warm, nutrient-rich domestic hot water systems, hot tubs, cooling towers, swimming pools and similar warm water environments. The Legionella bacteria can spread to humans through inhalation of aerosolized water droplets containing the bacteria This transmission can occur simply by breathing in the mist from a showerhead, or the steam from a hot tub. The American Society of Plumbing Engineers (ASPE), recommends that the outlet temperature at a storage type water heater be a minimum of 135° F to a maximum of 140° F to prevent the growth of legionella bacteria normally present in the water. Therein lies the quandary of risks between health hazard and injury hazard…
Rise to the occasion… the tempering valve! OR also known as mixing valves, water safety valves, and (more properly) thermostatic mixing valves or TMV’s. These devices function by blending hot water with cold water to ensure constant, safe, point-of-use or outlet temperatures thereby preventing scald hazards. Many TMVs use a wax thermostat for regulation. They also shut off rapidly in the event of a hot or cold supply failure to prevent scalding or thermal shock. Many states or municipalities now require that the temperature of all bath water in newly built and extensively refurbished domestic properties be controlled to a maximum of 118° F. Installing thermostatic mixing valves can ensure that water is delivered at the required temperature, thereby reducing the risk of scalding accidents; and also reducing hot water consumption from a supply that is maintained at a higher temperature.
So why all this talk about hot, too hot, and not hot enough?
The story I am about to tell you demonstrates that not all home accidents such as a scald from hot water are minor, and why often simple topics such as your water heater can have an impact in reducing safety hazards and risks in and around the home.
Note from BC Warner Home Inspections:
This story is from The Home Safety Council web site and can be viewed at their website. I am including it here to help spread the word about Home Safety to prevent such tragic accidents. I was recently reprimanded by a homeowner and and their agent for calling out a water temperature in excess of 138° Fahrenheit (see image above). They sneered and chose to call me “nit-picky” for calling attention to what they believed to be a trivial issue. Please read Leah’s story and understand why, regardless of who may be buying the home, I will continue to call out water temperatures of 121° Fahrenheit and higher.
Leah, a beautiful 11-month old baby girl and her older sister were visiting their grandparents’ new home. The grandmother left Leah sitting in the bath tub in less than 1″ of water. She was gone just long enough to bring Leah’s sister to the bath. During the 2 minutes she was gone, Leah apparently stood up in the bath tub and used the hot water lever for support, turning the hot water on full force into the tub. Because they were in a new home, no one had thought about checking or adjusting the hot water temperature, which was set in excess of 130° F at the water heater.
From her feet all the way to her chin, Leah suffered third degree burns over 90% of her tiny body. Even with the help and dedication of the best doctors in the country, Leah wasn’t able to win this battle for her life.
Leah passed away after 48 hours in the hospital — two days before her first birthday. If Leah had survived, she would have spent at least 20 months in the burn unit and required at least 30 operations before her 18th birthday.
The message I wish you to take from this story is that many home accidents are not trivial. They can be extremely serious with devastating consequences to the entire family. If we can prevent just one of those injuries, we will have made a difference. More than 90% of scalding incidents occur in the home. For children ages 14 and under, fires and burns are the leading cause of unintentional home injury deaths and it only takes seconds to change lives forever. Water heaters are normally set to temperatures above 131° F from the factory. At this temperature, a child can be scalded in less than 4 seconds. The time it takes to inflict a scald injury increases exponentially with every degree of temperature rise. The tender skin of very young children and the slow reaction time of the elderly and the handicapped make them most vulnerable to serious hot water burns. Scalding injuries are tremendously painful, and the effects can last for years.
If your home is not equipped with thermostatic mixing valves at the water heater or point-of-use faucets, please consider installing them. The device and labor is a moderate expense as compared to the cost of permanent scars… or a life.