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Hot Water Temperature Safety

Scalding, Legionella and Hot Water Heater Temperature Safety Solutions

Storage type water heaters are a reliable source of hot water and are used in most households in the U.S. and Canada. Even with advanced heating technologies that exist today, there are still technological limits to controlling hot water tank temperatures using a water heater.

There is a general misconception that a water heater’s thermostatic control can regulate the water temperature at the point-of-use. However, the water heater thermostatic control is typically at the bottom of the water heater, and does not sense the water temperature at the end point-of-use, which can pose a scald hazard for showers, faucets and other points in a household when water is too hot.

Hot water scalding is one of the major reasons why various plumbing codes and manufacturers require that thermostatic mixing valves be installed with water heaters to regulate water temperature at point-of-use.

Scalding Facts & Prevention

Keeping water in hot water storage tanks at a temperature that is considered sanitary requires raising the temperature of water to at least 140°F (60°C). But, at 140°F (60°C), water can cause third-degree burns in children in one second and in adults in five seconds.

The American Burn Association states that approximately 21,000 child injuries are directly related to dangerously hot tap water in residences—that’s 65% of all hospitalized burn-related injuries in children under 4 years old1. The answer to preventing harmful water temperatures is to store distributable hot water at a high temperature and temper it to a safer temperature before distribution to the fixture.

Cash Acme’s thermostatic mixing valves mix hot and cold water together upon exiting the storage tank to deliver water at a controlled temperature of 120°F or less to prevent scalding.

Legionella Facts & Prevention

Legionella is an aquatic bacteria that thrives in warm water environments and is the cause of Legionnaires Disease. It is commonly found in hot water heaters, potable water supplies, hot tubs, cooling towers, fountains, swimming pools, etc. and multiplies in conditions especially between 68 – 122 °F. The Legionella bacteria can spread to humans when breathed in.

An estimated 22K cases of Legionnaires disease are reported in the U.S. each year2. It is known to cause fever, chills, and a cough, which can be dry or may produce sputum. Some patients also have muscle aches, headaches, tiredness, loss of appetite, and, occasionally, diarrhea. Legionella may also cause cases of pneumonia that may be difficult to diagnose. Of the approximately 2.4 million cases of pneumonia that are diagnosed each year in the United States, about 18,000 are confirmed as Legionnaires Disease and up to 600,000 cases of Legionnaires Disease are misdiagnosed as pneumonia because the hospitals do not perform tests for Legionella.3

Improved design and maintenance of cooling towers, plumbing systems and hot water heaters to limit the growth and spread of bacteria are the foundations of Legionella prevention.

How the Issue is Being Addressed Around the World

The answer to preventing both Legionnaires disease and hot water scalding is to store distributable hot water at a high temperature and temper it to a safer temperature before distribution to the fixture.

A water temperature of 120°F does not kill the Legionella bacteria; a hot water temperature of 140°F is required at which Legionellae dies in 32 minutes. Hence it is recommended that the water heater be set at a safe hot water temperature of 140°F. The Legionella disinfection range is 158 – 176 °F.

Several countries around the world, including Canada and many in Europe, have adopted regulations requiring water to be stored at a higher temperature and delivered at 120°F or lower. The aggressiveness with which countries have addressed this issue indicates the importance of water storage safety. In fact, according to the Safe Kids Worldwide Campaign, “all code-making bodies at the [U.S.] national and regional level have established plumbing standards for newly constructed homes and residential units requiring anti-scald technology and a maximum water heater temperature of 120 degrees F.”4

In-home Solutions

Cash Acme Thermostatic Mixing Valves (TMVs) provide safe, in-home water solutions to both inhibit legionella tank growth and prevent water heater scalding and burns. Our TMVs allow water to be stored at high temperatures at the source (hot water heater) and delivered at safe temperatures at the point-of-use (sinks, lavatories, bathtubs or multiple fixtures such as gang showers). By placing a thermostatic mixing valve on a water heater, the heater’s thermostat can be turned up to a higher temperature setting to avoid growth of bacteria. The mixing valve then takes the hot water from the newly set heater and mixes it with cold water until it can be released from the valve at a safe 120°F temperature.

Additionally, the Cash Acme Tank Booster valve can double the hot water delivery in a system, as well as provide all of the other safeguards that our TMV products supply.

1 American Burn Association
2 CDC cases reported from 2000 – 2009: