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ASHRAE 12-2020 Guideline

The new Guideline 12 version takes a much closer look at how to manage the risk of Legionellosis. The challenge has changed from minimizing Legionellosis to managing Legionellosis. From minimizing to stopping cases.

It is important to note that the new standard implies that it isn’t necessarily a negative thing to get a test showing positivity. This should help the “head in the sand” syndrome that many in the industry still abide by. The “if I don’t know I have a problem then I don’t have a problem”. We all know that we should be proactive in stopping cases of Legionellosis. The only way we know if we are doing a good job and if we need to adjust our current strategy is to test. The new Guideline 12 “gives us permission” and says, “this is okay”.

Overall, the new version is written to be more easily adopted into code. However, this doesn’t mean it will be. It takes several years for new code to be adopted by various governing bodies.

The guideline much more detail on disinfection methods and the numerous risk factors within the plumbing system that effects the efficacy of your plan to minimize Legionellosis. It takes into consideration that things such as water quality, sediment and biofilm can decrease the efficacy of certain disinfectants. The guideline notes and calls attention to the fact that biofilm and sediment can wreak havoc on a plumbing system and decrease the efficacy of disinfectants and higher water temperatures.

The new version deemphasizes thermal shock and calls out its negative aspects. Temperature efficacy can be highly volatile due to changes in water quality. It should be noted that the standard industry temperature chart is based on laboratory testing, not real-world testing that takes into consideration fluctuating water quality, biofilm and sediment.

Guideline 12 specifically calls out water quality risk factors including sediment, disinfectant residual, temperature and water age. It speaks on the negative effects uninsulated or under insulated pipes, dead legs, long pipe runs, cold pipes near hot sources, biofilm, debris, sediment and water age can have on disinfectant efficacy. The only disinfectant that is not affected by these risk factors is copper silver ionization.

The guideline notes the possibility of municipalities adding disinfectant to the water supply and the fact that disinfectant residuals decrease as water travels to a building and through a building. Municipality disinfectant treatments are usually not high enough to properly reduced Legionella within a building’s plumbing system. The municipality disinfectant is also volatile. The municipality can change the level. They often do not let you know if the level has been changed. The level of disinfectant can also be affected by weather conditions and water main breaks.

In section five the guidleline recognizes electronic or sensor faucets have become very popular because of water conservation efforts. However, they can reduce flow and therefore deliver stagnant water. The guideline points out the need for cross connection and backflow prevention and especially to consider outlets that might not be as notable such as mop sinks. Another item to keep in mind is other equipment that can provide nutrients for bacteria. Particularly carbon filters.

There was no mention of thermal and chemical shock in the 2018 version. This is highly likely to have been included in the latest version due to COVID 19 and buildings which have been closed with dormant piping systems. While both thermal and chemical shock can have immediate effects in times of emergency, they are only useful at one point in time. Their effects decrease very quickly, and recolonization can happen very quickly. Both thermal and chemical shock also have the potential to cause major corrosion and other damage to plumbing systems and equipment.

LiquiTech Summary & Takeaways

  • As part of a multi-barrier approach install POE filtration to reduce sediment. LiquiTech’s Safe T Gard filters do not deplete disinfectant residuals as other filters can do.
  • Utilize copper silver ionization for potable water remedial treatment because of its long-term effectiveness.
  • Utilize copper silver ionization as a permanent disinfectant because it is not affected by the risk factors ASHRAE 12-2020 identifies, it does not cause corrosion, there is no scalding risk and no risk to humans.
  • The new guideline noted a wider temperature range for optimal Legionella growth. Copper silver’s efficacy is not affected by temperature.
  • The guideline emphasized that a positive Legionella test isn’t necessarily a bad thing. Testing should be done on a regular basis as a preventative and pro-active approach to reducing the risk of Legionella.
  • Create a flushing protocol if you don’t already have one.
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