temperature shall be boosted from 60C (140F) to 82C
Domestic hot water return circuits of substantially
(180F) for final sanitizing rinse. Heat pump hot water
varying pressures as result of pressure zoning or static
heaters shall be used where possible to save energy.
head cannot successfully be joined to a single pressure
zone water heater. Locate individual pressure zone water
Emergency fixtures: eyewash (0.4 gpm per fountain), face
heater(s) within the pressure zone(s), where return
wash (3 gpm each), or shower (20 gpm each) shall be
pressures would vary substantially causing dead head
tempered immediately at the fixture or group of fixtures
on the lower pressure return circuits. Hot water return
(within 25 feet) to deliver "tepid water" 29C (85F) -
systems shall have circuit setters (balancing valves) and
<37.8C (100F), at 0.207 megapascal (30 psi), within 10
test plugs at each return circuit, and systems shall be
seconds, for a minimum period of 15 minutes, and shall
balanced.
account for temperature drop across the valve (generally
7C or 20F) at flow.
Domestic Water Supply Equipment. Domestic water
supply equipment and components shall include, but not
There shall be no dead legs or capped spurs within the
be limited to, the following equipment: water meters,
potable domestic water plumbing system, without return
water heaters, water filtration, water softening, pressure
circulation. Rubber fittings and device components shall
booster systems, pressure regulating valves, circulating
not be permitted within the potable domestic hot water
pumps, backflow preventers, circuit setters/balancing
or return systems, as they have been associated with
valves, thermostatic mixing valves, expansion tanks,
persistent colonization of Legionella spp. For additional
isolation valves, hangers and supports, and thermal
information on water temperature, control of Legionella
insulation.
spp., and water safety, refer to the Center for Disease
Control (CDC) "Guidelines for Environmental Infection
Water heaters and expansion tanks shall be compliant
Control in Healthcare Facilities" (section 5 "Maintenance
with ASME, stamped and rated.
Procedures Used to Decrease Survival and Multiplication
Water hammer arrestors shall be provided at each
of Legionella spp. in Potable-Water Distribution
elevation change of every horizontal branch to fixture
Systems") and ANSI Standard Z358.1 (1999) "Emergency
batteries, at all quick-closing automatic valves
Eyewash and Shower Equipment." Distribution system shall
(mechanical make-up, drinking fountains, flush valves,
consist of a piping system that connects water heater(s)
single lever control faucets, temperature regulating valves,
to all fixtures, equipment, and outlet demands requiring
dishwashers, return pumps, and similar), and at each floor
potable domestic hot water. Circulation return systems
on each horizontal main for branches with/without
with circuit setters/balancing valves, or temperature
individual fixture or battery water hammer arrestors, for
maintenance systems shall be provided for all branches
both hot and cold water. Water hammer arrestors shall be
in excess of 25 feet from the water heater or circulated
compliant with the Plumbing and Drainage Institute
distribution main. Domestic hot water shall be available
(PDI) Standard PDI-WH201, ANSI/ASME A112.26.1M,
at each hot water outlet within 15 seconds of the time
or as required by code, and as recommended/required by
of operation.
fixture and equipment manufacturer, or warranty.
161
MECHANICAL
ENGINEERING
5.18
Plumbing Systems
Revised March 2005 PBS-P100
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