Scald Protection By The Numbers
We've all had it happen - someone inadvertently flushes a toilet while we're in the shower and we get an abrupt wake-up call! While the scenario has been humorously portrayed in scripted entertainment for years, it really isn't a laughing matter. The threat of serious injury from scalding and slip-and-fall accidents associated with thermal shock is serious business. So much so that the American Society of Sanitary Engineering initiated its first pressure-balancing and thermostatic control valve standard - No. 1016 - back in November 1973. That original standard was written to address the original issue: thermostatic- or pressure-balancing needed essentially at the point of use. Back in those days, the focus on safety was primarily relegated to the bather in either a tub or shower installation.
Like so many things in life, advancements in plumbing products and designs aimed at enhancing peoples' quality of life often can create new challenges. When those challenges arise, the natural thing to do is attempt to govern them with existing guidelines. That is precisely what has occurred with many new products, such as single-temperature sensor faucets and showers. Even designs such as gang or multiple showers in school gyms that often need to deliver a centrally pre-set, constant-temperature water flow beyond the control of the bather needed to be addressed.
These multiple shower applications are more complex than a single shower controlled by a bather. Because there was a void of appropriate standards to properly cover these applications and designs, they often were covered under ASSE 1017. Frankly, this occurred because that standard was all that existed.
Let's stop for a moment and consider the hazards - scalding and thermal shock. Although scalding is less frequent than thermal shock, the risk and severity of scalding incidents drastically increases with a relatively small increase in water temperature. That's because scalding generally involves immersion or exposure of large portions of the body to heated water. For example, at 140 degrees F, an exposure of five seconds will produce second-degree burns.
Thermal shock is a rapid and uncomfortable change in water temperature caused by pressure changes in the hot or cold water supplies. Thermal shock usually causes an abrupt physical reaction, which can be as simple as pulling your hands out from a lavatory sink water flow or a reflexive flight response from a tub or shower. While neither of these abrupt reactions is very appealing, fleeing a wet and slippery shower or tub can be significantly more dangerous because of slip-and-fall accidents.
To protect public safety and provide guidance to manufacturers, specifiers and code authorities regarding the widening array of products and application configurations, the ASSE 1016 Standard Development Working Group, while revising the current standard, looked at the need for additional standards. It was determined that three separate standards were needed to properly identify and guide the three distinct categories of products and design/use configurations: ASSE Standard 1016, ASSE 1069 and ASSE 1070. We'll review them here, as well as ASSE 1017.
It should also be noted that there are other standards that govern temperature or pressure changes, as well as individual pressure-balancing or inline valves. These standards will not be reviewed here because the new generation of 1069 and 1070 standards does not substantially impact them.
ASSE 1016 - Performance Requirements For Individual Thermostatic, Pressure-Balancing And Combination Pressure-Balancing And Thermostatic Control Valves For Individual FixturesHistorically, the applications to be guided by ASSE 1016 are devices that provide scald and thermal shock protection to individual showers and showers in combination showers/bathtubs. This standard's shower focus is reinforced by the fact that the standard requires these devices to maintain a set temperature at 2.5 gpm, which is the maximum flow rate of a showerhead. Lower flow-rated valves are not subject to guidance from ASSE 1016. The standard requires devices to:
- Be controlled by the bather or the bather's attendant (clearly identified as the "user");
- Incorporate an adjustable means to limit the maximum temperature setting that can, for example, provide a level of scald protection for the tub in tub/shower applications;
- Reduce hot water flow when a cold water supply failure occurs; and
- Maintain an outlet water temperature within ±3 degrees F of the set position.
ASSE 1069 - Performance Requirements For Automatic Temperature Control Mixing ValvesThis proposed new standard is being developed primarily for gang or group shower applications where, for example, a single pipe provides single temperature water to multiple showerheads. This can be accomplished using metering valves, sensor-actuated showers or a simple manually operated on/off valve. A critical performance differentiator for 1069 devices is that mixing of water is not allowed downstream of the 1069 device. So, 1069 devices provide thermal shock and scald protection, and test procedures take into consideration the effects of pressure disturbances on both the hot and cold water supplies to the device.
ASSE 1070 - Performance Requirements For Water Temperature-Limiting DevicesThis new standard provides system design flexibility, where the application is not subject to thermal shock concerns. ASSE 1070 primarily establishes guidelines for inline tempering devices that limit the maximum hot water temperature that a fixture fitting can discharge. It should be noted that this device could be integral to the fixture or external as an inline device supplying tempered water only to the hot side of the fixture fitting. These devices will provide a level of scald protection by limiting the maximum temperature, but because further mixing of water is allowed downstream of the device, no thermal shock protection is provided.
ASSE 1017 - Performance Requirements For Temperature-Actuated Mixing Valves For Hot Water Distribution SystemsASSE 1017 is included in this discussion because devices covered by this standard often are specified in combination with downstream temperature-limiting devices covered by ASSE 1016, 1069 and 1070. This multiple-tiered specification approach is widely accepted by specifiers.
This standard addresses thermostatic mixing valves that are located at the heat source and used for a general reduction of hot water service temperatures delivered to the water distribution system. Final temperature control at fixture outlets is required via other suitable mixing devices. ASSE 1017 requires covered devices to:
- Be located at the hot water source, thus nullifying any effect that fluctuating pressure differentials between the hot and cold water supplies would have on outlet temperature; and
- Maintain a mixed water temperature within the permissible tolerance from 3 degrees F to 7 degrees F, depending on the flow capacity of the device.
Scald and burn incidents, as well as the slip-and-fall accidents that often accompany them, are a continuing health and safety risk to the public. The changes being made to the appropriate ASSE standards are designed to mitigate additional risks by clearly establishing the requirements for an ever-widening array of products and design applications. Specifiers, contractors and code writers are encouraged to become thoroughly familiar with the requirements and available product alternatives.