also affect Legionella growth in other parts of the plumbing
system. If the tenant is responsible for maintaining a cooling
tower that could affect people in its building as well as other
buildings on the campus, ensure the tenant’s cooling tower
maintenance complies with your WMP.
2) Include All At-Risk Water Systems
Standard 188 requires WMPs to account for cooling towers,
whirlpool spas, ornamental fountains, water features, misters,
air washers and humidifiers. For plumbing systems, however,
the standard requires a WMP only if the building has any of
■ A centralized hot water system
■ More than 10 stories
■ Housing designated for people over 65
■ Patients staying longer than 24 hours
■ An area housing or treating people who are immunocompromised or otherwise more susceptible than the general
population to Legionella infections.
How you apply the first two factors – centralized hot
water systems and the number of stories – is crucial to risk
All other factors being equal, a centralized domestic hot
water system (for example, ground floor water heaters supplying hot water to faucets with recirculation back to the heaters)
is typically more prone to Legionella growth than a system that
supplies only cold water to faucets with tankless heaters underneath. But other non-centralized domestic hot water configurations – such as small tank-type water heaters for apartment
units or sets of common-area restrooms – may actually be more
prone to Legionella growth than a centralized system with
It’s also not uncommon to find Legionella in samples collected from domestic cold water systems, especially during the
summer when the water may not be all that cold.
Think carefully about the number of stories as well. Larger
piping networks are generally more prone to Legionella growth
than ones found in single-family homes or small office buildings, but Legionella testing data indicates that you’d be foolish
to assume a building is free of Legionella because it has 7 stories
instead of 11.
Consistency is key to making good decisions. If you have
authority over several buildings and only some of them have an
ASHRAE 188 risk factor, be consistent with control measures
regardless of your decision about establishing a WMP.
Let’s say you have 20 buildings in your portfolio, 15 of which
Control Measure Number: DWM32 Category: Domestic Water System Maintenance
Keywords stagnation, supply feeds
Control Measure Either keep all water feeds open or flush offline feeds to waste before
opening to building.
Locations PWMTs, POEs
Monitoring If all feeds are kept open, monitor monthly water bills to ensure adequate
flow through each. If all feeds are not kept open, affix a sign to the offline
feeds, instructing to flush to a drain before use. Inspect and document
flush-to-waste procedure each time offline feeds are opened.
Frequency of Control Measure Task Every 30
Frequency of Compliance
Every 1 Years
Limits If all supply feeds are used, water bills must show similar flow among
feeds or adequate flow in each. Before opening offline feeds to the
building, they must be flushed to a drain long enough to empty the
pipe volume at least 10 times.
Corrective Action Install valves and drain as necessary to flush to waste on each feed
that is not left open. Keep all feeds open if valves are not in place to
flush to waste or if flushing is not performed per limits before each
opening. If water bills indicate inadequate flow through one or more
feeds, have engineer or contractor suggest solutions for evening the
flow (e.g., partially closing one of the valves).
Suggested Training 4. 24
Date Compliance Last Verified 1/15/2016
Documentation Both are kept open. Water bills indicate adequate flow through each.
Verification Person Facility director
Due Date for Next Verification
THIS IS ONE OF
WATER MAINTENANCE CONTROL
MEASURES in our
measures should be
included for maintenance of other water
systems as well, such
as cooling towers,
and whirlpool spas.
A water management plan should also
include measures to
take during design and
construction, procedures for managing
incidents such as water
main breaks and temporary system shutdowns, and a plan for
responding to cases of
SAMPLE WMP CONTROL MEASURE