Code Classroom Continued from page 18
Disease testing. It may also be attributable to lower flow shower heads that break up shower head discharge flows into a finer mist, making the water easier to inhale. We know how to prevent Legionellae bacteria from
growing in the plumbing systems, and we have simple cost effective strategies to use. People do not have to lose their lives. With a mortality rate of nearly 40%, Legionnaires Disease continues to be among the dead- liest preventable diseases known to us. Why do we see a preventable disease continuing to
increase? There can be many reasons, including the fact that the CDC has taken the position that, if you look for Legionellae bacteria, you are going to find it and, unless you can prove that the bacteria is causing a particular illness, there is nothing that a hospital, nursing home or facility with an at-risk population is required to do. The CDC’s position does not go as far as requiring
testing. It states that, unless there are two confirmed cases within a six-month period, a hospital is not oblig- ated to do anything to clean up its water. Testing patients for Legionellae could be discouraged, because they might find it and would then be obligated to spend money to do something about it. If the patient dies, it can be written off as common pneumonia. The absence of safe water protocols by the CDC gives
hospitals an excuse to do too little. Too many people are losing their lives unnecessarily. A book titled Legionellae Control in Health Care Facilities, a Guide for Minimizing Risk by Matthew R. Freije and James M. Barbaree, Ph.D. is an excellent reference book for any facility (healthcare or otherwise) that either is con- cerned about Legionellae in its water systems or that wants to establish a proactive program to reduce the risk of the bacteria in their water supply. The engineering community and the plumbing com-
munity need to be more proactive in designing preven- tative measures into plumbing systems. Copper silver ionization units on the water supply to the hospital and ultra-violet radiation units on circulated hot water sys- tems have proven to be effective at limiting Legionellae bacteria growth in the water supply. Hot water storage temperatures above 135 to 140 degrees Fahrenheit, which is hot enough to kill the bacteria, should also be utilized. Hot water systems should also be circulated to prevent stagnant areas where bacteria can grow. Temperature-actuated master mixing valves can be used where appropriate to limit the distribution temperatures to a safe temperature that will not increase scalding haz- ards, or point-of-use temperature limiting devices should be used to prevent scalding. A good design uses this method to balance the concerns of Legionellae with the concerns for scalding and thermal shock. The speaker mentioned that she had a conversation a
few months back with the author of the Occupational Safety & Health Administration (OSHA) Technical Manual on Legionnaires Disease. OSHA regulates Legionellae in the water but does not require proactive prevention. The author of the manual said, “The absence of strong guidance from the CDC on this topic amazes me. They are lax. If the disease you are tracking is con-
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tinuing to increase why bother tracking it if you aren’t going to do anything about it.” Although we currently lack federal regulations, there
are literally dozens of Legionellae prevention guidance documents available for designers and engineers from such organizations as the Department of Defense (DoD), the Veterans Administration (VA), the American Water Works Association (AWWA), Occupational Safety & Health Administration (OSHA) and the American Society of Heating Refrigeration and Air-con- ditioning Engineers (ASHRAE). One organization is taking a big step forward for
water safety. Last year, ASHRAE released a draft stan- dard for preventing Legionellae associated with build- ing water systems. This will be the first standard of its
The engineering community and the plumbing community need to be more proactive in designing preventative measures into plumbing systems. Copper silver ionization units on the water supply to the hospital and ultra-violet radiation units on circulated hot water systems have proven to be effective at limiting Legionellae bacteria growth in the water supply.
kind and, when it is published, it will arguably result in a shift of responsibility being placed on building own- ers, mechanical engineers and contractors to proactive- ly address Legionellae prevention. I would encourage you to learn everything you can
about the latest research surrounding Legionellae pre- vention, and I would strongly encourage you to become familiar with the new ASHRAE standard 188. The ASHRAE standard uses simple strategies, but it is going to require more than just removing dead legs in the hot water piping system, elevating the temperature of hot water storage tanks and keeping water moving with recirculation systems. Studies have now shown that those common practices are not enough. The ASHRAE standard takes into account that the
difficulty with Legionellae is that it can survive in a wide range of temperatures, with its ideal growth range being between 95 F-118 F. This is precisely in the tem- perature range at which hot water is delivered in a hos- pital and in most other types of facilities. The ASHRAE standard is going to require not only that domestic hot water be circulated but also that this be done with a min- imum return of 124 F in healthcare buildings, thus keep- ing the water out of the ideal growth range parameters. This certainly may change the way that you have been
designing your domestic hot water systems. The elevat- ed supply temperature is needed to meet the ASHRAE standard and will also mean that there is a need to use localized mixing valves that conform to ASSE 1070 or
March 2011
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