User Guide

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Figure 4-3: System parameters
Step three
Develop water size charts for
each pipe material and water
temperature. (See Figures 4-3
and 4-4.)
Designer must know the
following:
• Pipe materials being
designed and range of
sizes for each system
• Supply and return design
water temperatures
Note: For commercial
systems, size domestic
hot-water return piping
per the requirements
stated in ASPE Plumbing
Engineering Design
Handbook, Volume 2,
Plumbing Systems
• Maximum velocity of each
pipe material per water
temperature
• Table approved by the local
authority having jurisdiction
(AHJ) or referenced
plumbing code table for
converting gallons per minute
(gpm) to water supply xture
units (WSFU)
• If the domestic cold-
water system demand is
predominately ush valve or
ush tank WSFU
Step four
Apply the appropriate water
size chart to the plumbing
design. Calculate WSFU
demand per pipe segment by
adding all the WSFUs of the
xtures being supplied by that
pipe segment. (See Figure
4-5.)
Figure 4-2: Determine the friction loss per foot (or per 100 feet) of pipe