Water Temperature
The first control point is the proper setting of the temperature for your water heater. If your water heater is used exclusively for use in faucets, bathtubs, showers, and appliances it should be set at a maximum of 120 deg F. Most hot water heater manufacturers have this as the factory set point. The plumbing code allows a 140 deg F water temperature if the water heater has domestic use and is used as a heating source.
Tub and Shower Valves
Industry safety experts have chosen 120°F (49°C) to be the maximum safe water temperature for showering and bathing purposes. In a showering application where the shower head is fixed, a user subjected to a surge of high-temperature water usually reacts by abruptly moving away from the hot spray. This abrupt movement often causes falls, resulting in the stunned user not being able to escape the scalding water stream. Children and some elderly persons often have delayed or no physical reaction to the scalding water such that they continue to stand in the stream. Therefore, showers and combination tub/showers must have a shower control valve that is capable of protecting an individual from being exposed to water temperatures in excess of 120°F (49°C). The control valve must be installed at the point of use. In other words, the person in the shower must have access to the control handle(s) of the valve.
The control valve must be designed to protect against two types of events: (1) extreme temperature fluctuations from the user’s set temperature caused by changes in hot or cold-water distribution line pressures and (2) extreme temperature conditions caused by the user either purposely or accidentally adjusting the control valve to deliver the hottest water available from the hot water distribution system. Where water inlet pressures or temperatures fluctuate during shower use, control valves complying with ASSE 1016/ASME A112.1016/CSA B125.16 must automatically and rapidly adjust to maintain the water discharge temperature to ±3.6°F (±2°C) of the user-selected temperature.
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The standards also require that shower control valves have a maximum temperature-limit device that is not adjustable by the user at the point of use. The high-limit stop is typically an adjustable set screw or cam that is manually set to limit the travel of the control valve handle. The high-limit stop must be field adjusted at the time of installation to limit the delivered water temperature to a maximum of 120°F (49°C).
Types of Shower / Tub Valves
The three types of shower control valves available are pressure balancing, thermostatic and combination thermostatic/pressure balancing. A pressure-balancing valve senses changes in pressure of the hot and cold-water supplies (up to 50-percent pressure change). If the pressure on one side changes, the valve reacts so that the flow from each side of the valve is adjusted to maintain the user’s temperature selection. The thermostatic valve senses the discharge water temperature and adjusts flows of supply water to the valve to maintain the user’s set temperature. A thermostatic valve provides some limited protection against hot and cold supply pressure fluctuations (up to 20-percent pressure change). A combination thermostatic/pressure-balancing valve adjusts to changes in supply pressures (up to 50-percent pressure change) and discharge temperature.
Pressure-balancing control valves are used in a majority of shower applications. One slight disadvantage of the pressure-balanced-type control valve is that any change in the temperature setting of the water heating system will affect the maximum discharge temperature available from the control valve. If the system temperature is lowered, some users might complain that they are not receiving hot enough water. If the system temperature is raised, the maximum water temperature available from the valve might be in excess of 120°F (49°C). Seasonal fluctuations in the cold-water supply temperature can also affect the maximum discharge temperature. Thus, pressure-balancing-type control valves might require periodic readjustment of the high-limit setting.
The maximum discharge temperature from a thermostatic-type control valve is not affected by changes in the temperatures of the hot and cold-water supplies to the valve except for when the hot water supply temperature falls below the high-limit setting. Although this type of valve might significantly reduce the need for readjustments to the high-limit setting, due to its inherent limited protection against supply-side pressure changes, a thermostatic valve might not be suitable for applications where large pressure fluctuations (greater than 20-percent change in pressure) are expected.
A combination pressure balanced/thermostatic control valve offers the greatest degree of protection for the shower user. As the name implies, this type of valve offers the best features of both the pressure-balanced-type valve and thermostatic-type valve designs.
Valve information from ICC Code Commentary
Testing and Maintenance
While the combination of water heater temperature setting, and the use of a protective shower valve may seem to have solved this problem, testing and maintenance is a key part of the process.
Initial testing and setting of the temperature at the water heater and the output from the valves should be measured with a thermometer. Testing the valves under foreseeable use conditions such as flushing a toilet and operating other plumbing devices should be conducted. As these are mechanical devices, you should periodically test the valves and settings to assure they remain safe.
The Driehaus Difference
Before the verdict was returned we identified scald injuries as a loss source in our article Risk Management Strategies of Landlords. Â We want our clients to be aware of exposure and take the appropriate actions to prevent losses and injuries. We want to be your insurance provider, so call us at 513-977-6860 or contact us via our website at www.driehausins.com
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