Page 927 - 2018_IRC

APPENDIX P

included, use manufacturers’ tables and velocity rec- air-conditioning cooling towers. Future demands
ommendations. placed on the public main as a result of large growth or
expansion should be considered. The available pressure
Note: For all examples, the following metric conversions are
applicable. will decrease as additional loads are placed on the pub-
lic system.
1 cubic foot per minute = 0.4719 L/s.
2. Demand load. Estimate the supply demand of the
2
1 square foot = 0.0929 m . building main and the principal branches and risers of
1 degree = 0.0175 rad. the system by totaling the corresponding demand from
the applicable part of Table AP103.3(3). When estimat-
1 pound per square inch = 6.895 kPa. ing peak demand, sizing methods typically use water
1 inch = 25.4 mm. supply fixture units (w.s.f.u.) [see Table AP103.3(2)].
This numerical factor measures the load-producing
1 foot = 304.8 mm. effect of a single plumbing fixture of a given kind. The
1 gallon per minute = 3.785 L/m. use of fixture units can be applied to a single basic
probability curve (or table), found in the various sizing
AP103.3 Segmented loss method. The size of water service
mains, branch mains and risers by the segmented loss methods [see Table AP103.3(3)]. The fixture units are
method, must be determined by knowing the water supply then converted into a gpm (L/m) flow rate for estimat-
demand [gpm (L/m)], available water pressure [psi (kPa)] and ing demand.
friction loss caused by the water meter and developed length 2.1. Estimate continuous supply demand in gpm (L/m)
of pipe [feet (m)], including the equivalent length of fittings. such as for lawn sprinklers, air conditioners, etc.,
This design procedure is based on the following parameters: and add the sum to the total demand for fixtures.
The result is the estimated supply demand for the
1. The calculated friction loss through each length of pipe.
building supply. Fixture units cannot be applied to
2. A system of pressure losses, the sum of which must not constant-use fixtures, such as hose bibbs, lawn
exceed the minimum pressure available at the street sprinklers and air conditioners. These types of fix-
main or other source of supply. tures must be assigned the gpm (L/m) value.
3. Pipe sizing based on estimated peak demand, total pres- 3. Selection of pipe size. This water pipe sizing procedure
sure losses caused by difference in elevation, equip- is based on a system of pressure requirements and
ment, developed length and pressure required at the losses, the sum of which must not exceed the minimum
most remote fixture; loss through taps in water main; pressure available at the supply source. These pressures
losses through fittings, filters, backflow prevention are as follows:
devices, valves and pipe friction.
3.1. Pressure required at the fixture to produce
Because of the variable conditions encountered in hydrau- required flow. See Section P2903.1 of this code
lic design, it is impractical to specify definite and detailed and Section 604.3 of the International Plumb-
rules for the sizing of the water piping system. Current sizing ing Code.
methods do not address the differences in the probability of
use and flow characteristics of fixtures between types of 3.2. Static pressure loss or gain (because of head) is
occupancies. Creating an exact model of predicting the computed at 0.433 psi per foot (9.8 kPa/m) of
demand for a building is impossible and final studies assess- elevation change.
ing the impact of water conservation on demand are not yet 3.3. Loss through a water meter. The friction or
complete. The following steps are necessary for the seg- pressure loss can be obtained from the manufac-
mented loss method. turer.
1. Preliminary. Obtain the necessary information regard- 3.4. Loss through taps in water main [see Table
ing the minimum daily static service pressure in the AP103.3(4)].
area where the building is to be located. If the building 3.5. Loss through special devices, such as filters,
supply is to be metered, obtain information regarding softeners, backflow prevention devices and
friction loss relative to the rate of flow for meters in the pressure regulators. These values must be
range of sizes to be used. Friction loss data can be obtained from the manufacturers.
obtained from manufacturers of water meters. Enough
pressure must be available to overcome all system 3.6. Loss through valves and fittings [see Tables
losses caused by friction and elevation so that plumbing AP103.3(5) and AP103.3(6)]. Losses for these
fixtures operate properly. Section 604.6 of the Interna- items are calculated by converting to the equiv-
tional Plumbing Code requires that the water distribu- alent length of piping and adding to the total
tion system be designed for the minimum pressure pipe length.
available taking into consideration pressure fluctua- 3.7. Loss caused by pipe friction can be calculated
tions. The lowest pressure must be selected to guaran- where the pipe size, pipe length and flow
tee a continuous, adequate supply of water. The lowest through the pipe are known. With these three
pressure in the public main usually occurs in the sum- items, the friction loss can be determined using
mer because of lawn sprinkling and supplying water for Figures AP103.3(2) through AP103.3(7). Where

902 2018 INTERNATIONAL RESIDENTIAL CODE ®
Copyrighted © 2017 by, or licensed to, ICC (ALL RIGHTS RESERVED); licensed to UL, LLC pursuant to License Agreement with ICC. No further reproductions authorized or distribution authorized.
ANY UNAUTHROIZED REPRODUCTION OR DISTRIBUTION IS A VIOLATION OF THE FEDERAL COPYRIGHT ACT AND THE LICENSE AGREEMENT; AND SUBJECT TO CIVIL AND CRIMINAL PENALTIES THEREUNDER.