Maintaining ANSI temperature requirements for multiple showers
Answered by Casey Hayes, director of engineering, Haws Corp., Sparks, NV.
Prior to the 2004 revision of the ANSI Z358.1 standard, the specific temperature requirement for outlet water was somewhat loose, mandating only that the water be "tepid." With the 2004 revision, the temperature range was clearly established to be between 60° F and less than 100° F, at the requisite 20-gallon-per-minute flow rate, for the full 15-minute use cycle. The flow rate and drench cycle provisions were unchanged from previous requirements.
There are no provisions for moderating the temperature range requirement in the event of multiple-victim incidents, which means each single shower must comply as a standalone circumstance. This poses a significant challenge in many applications, as water pressure, volume and – importantly – tempered water capacities must be adequate for the worst-case multiple-victim circumstances that may be encountered.
It's also important to realize that nowhere in the requirement does ANSI state that the temperature range does not have to be met if there is a water supply interruption or failure. So, accommodations should be made to substantially ensure continued service, even in the event of water supply failures. While a complete loss of input water would be impossible to overcome within the specification of a tempering system, a number of other significant failures or interruptions should be addressed in system design. These may include water temperature and pressure fluctuations, loss of hot water supply (requiring a full-flow bypass capability in the mixing valve design) and other noncatastrophic circumstances. Measures – including redundancies in the system design – can and should be taken to allow the system to function as well as possible, even during significant (noncatastrophic) water supply interruptions or fluctuations. The regulatory direction established by ANSI Z358.1 aside, common sense dictates that reasonable redundancies are prudent and in the best interest of one's employees and others.
Specifiers are urged to seek the assistance of packaged tempering system manufacturers when designing systems to address their individual needs. Packaged system manufacturers are in the best position to assist, as they deal with complicated applications daily and are conversant on the latest component developments and best practices.