ASHRAE Journal - June 2020 - 73

COLUMN IEQ APPLICATIONS

that is fatal in 10%-33% of cases.4,5 When its growth in
building water systems is not controlled, the bacteria
can be distributed in aerosolized water from common
ﬁxtures, such as showers, ice machines, fountains,
and even toilets and taps. Inhaling bacteria-contaminated droplets can lead to Legionnaires' disease.
Legionnaires' disease is already a signiﬁcant health
concern, and reported cases in the U.S. have increased
six-fold between 2000 and 2018.4 Proper water management during low or no occupancy is critical to
ensuring stagnant water does not lead to a spike in
cases as the population returns to work and travel.
Good water management is possible while buildings aren't experiencing normal use. At the time of
this column's writing, governments had taken steps
to designate water treatment professionals and
other personnel servicing water systems as essential
personnel, exempt from stafﬁng reduction requirements. Absenteeism is a major concern in the water
industry,6 so it is understandable if maintenance
procedures or the frequency with which those procedures are run needs to be ﬂexible. Even with this ﬂexibility, water maintenance staff and engineers who
pragmatically follow best practices can take certain
steps to maintain public health and avoid exposure to
waterborne bacteria in buildings.
According to ANSI/ASHRAE Standard 188-2018 and
the CDC Toolkit, there are four fundamental ways
to keep building water safer during normal operations and when the building is experiencing low or no
occupancy:7,8
1. Keep cold water cold.
2. Keep hot water hot.
3. Keep water moving.
4. Keep the entire system clean.
L. pneumophila grow at a wide range of temperatures, but they grow best at 85°F-108°F (29°C-42°C).9
Therefore, it is critical to follow ASHRAE guidelines to
store hot water at or above 140°F (60°C), deliver hot
water at or above 124°F (51°C), and store cold water
at or below 68°F (20°C).10 While these are straightforward guidelines to follow under normal circumstances, it may be tempting to some operators to set
back water temperatures while the building is not in
use. This could create public health risks-hot water
supply temperature should be set as high as practical and allowed and cold water should be monitored

for any increase in temperature that may approach
68°F (20°C). These are the easiest controls to put in
place prior to considering addition of any secondary
disinfectant.
Stagnant water reduces disinfectant levels and the
efﬁciency of the disinfectant to reach all areas of the
building. To maintain proper disinfectant residuals and
temperature, water should be kept moving through the
system. Flushing should be performed regularly, ideally weekly.11 According to the Environmental Science,
Policy, and Research Institute (ESPRI), "Flushing clears
out the low quality water that accumulated during
low use and replaces it with high quality water from
the municipal supply. The fresh water will help mitigate the problems...that emerged while the water was
stagnant."11
Maintaining the cleanliness of ﬁxtures, especially
those that can produce aerosols, like shower heads, will
also mitigate exposure to L. pneumophila. Having cleaning
procedures in place for water-aerosolizing ﬁxtures can
help reduce exposure.
These simple actions can help maintain higher
water quality during a shutdown and help mitigate
the risk posed by L. pneumophila. In many cases, testing for L. pneumophila to validate that these actions are
working properly may also be appropriate, especially
if these practices cannot be adhered to strictly due
to stafﬁng concerns. Building owners and engineers
should follow ASHRAE Standard 188-2018 when
identifying test providers, including working with an
accredited laboratory.8
Many buildings may not have had the staff or
resources to maintain proper temperature or ﬂushing procedures during shutdown or periods of low
occupancy. In this case, following proper recommissioning steps is critical to ensure the building can
be safely reoccupied. ESPRI suggests that a single
ﬂush, especially of a complex building water system,
may not be sufﬁcient to reestablish water quality.11
Ongoing ﬂushing is required, and the longer service
is interrupted, the greater the level of effort required
for restoration.
The Water Research Foundation (WRF) recommends
several consecutive weeks of ongoing ﬂushing for a
Jeff Bates is project manager and Patsy Root is regulatory affairs manager at IDEXX
Laboratories in Westbrook, Maine. Root is a member of SPC 514P, Minimizing Risk of
Disease, Injury Associated with Building Water Systems.
J U N E 2020

ashrae.org

ASHRAE JOURNAL

https://www.ashrae.org/

ASHRAE Journal - June 2020

Table of Contents for the Digital Edition of ASHRAE Journal - June 2020