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10.14.1 Maximum Velocity (See Appendix B.6)
Water distribution piping within buildings shall be sized for a maximum velocity of 8 feet per second at the design flow rate unless the pipe manufacturer's sizing recommendations call for the maximum velocity to be less than 8 feet per second. The maximum velocity of hot water in copper tubing shall be 5 feet per second.
10.14.2 Size of Individual Fixture Supply Branches
  1. Individual fixture supply branch pipe sizes shall be based on the minimum available flowing water pressure at its point of connection to the water distribution system, any elevation difference between that connection and the fixture, and the allowable pressure loss in the fixture supply branch. The minimum fixture supply branch pipe sizes shall be as indicated in Table 10.14.2A. For design purposes, the required pressure at each fixture inlet shall be 15 psig minimum flowing, except 20 psig minimum flowing for flushometer valves on siphon jet water closets and 25 psig minimum flowing for flushometer valves on blowout water closets and blowout urinals. Flushometer tank (pressure assisted) water closets require a minimum of 25 psig static pressure. The following water flow rates shall be used for the purpose of sizing individual fixture supply branch pipes:
    5.0 gpm for hose bibbs and wall hydrants;
    4.0 gpm for bath faucets and clothes washers;
    0.75 gpm for drinking fountains and water coolers;
    2.2 gpm for sink faucets;
    2.5 gpm for shower heads;
    2.2 gpm for lavatory faucets;
    3.0 gpm for water closets other than the flushometer valve type;
    12.0 gpm for flushometer valve urinals;
    30.0 gpm for flushometer valve water closets
  2. Fixture supply branches shall extend from the distribution system to within 30 inches of the point of connection to the fixture or device served and be within the same area and physical space as the point of connection to the fixture or device. Fixture supply tubes and flexible water connectors shall be not less than the size recommended by the manufacturer of the fixture, faucet, appliance or device served.
    Table 10.14.2A
    WATER SUPPLY FIXTURE UNITS (WSFU) AND MINIMUM FIXTURE SUPPLY BRANCH PIPE SIZES
    HEAVY-USE ASSEMBLY
    OTHER THAN DWELLING UNITS
    SERVING 3 OR MORE DWELLING UNITS
    INDIVIDUAL DWELLING UNITS
    MINIMUM SUPPLY BRANCH PIPE SIZE
    BATHROOM GROUPS HAVING 1.6 GPF WATER CLOSETS OTHER THAN THE FLUSHOMETER TYPE
    Half-Bath or Powder Room 3.5 2.5
    1 Bathroom Group 5.0 3.5
    1-1/2 Bathroom Groups 6.0 4.0
    2 Bathroom Groups 7.0 4.5
    2-1/2 Bathroom Groups 8.0 5.0
    3 Bathroom Groups 9.0 5.5
    Each Additional Half-Bath 0.5 0.5
    Each Additional Bathroom Group 1.0 1.0
    BATHROOM GROUPS HAVING 3.5 GPF (or higher) GRAVITY TANK WATER CLOSETS
    Half-Bath or Powder Room 4.0 3.0
    1 Bathroom Group 6.0 5.0
    1-1/2 Bathroom Groups 8.0 5.5
    2 Bathroom Groups 10.0 6.0
    2-1/2 Bathroom Groups 11.0 6.5
    3 Bathroom Groups 12.0 7.0
    Each Additional Half-Bath 0.5 0.5
    Each Additional Bathroom Group 1.0 1.0
    OTHER GROUPS OF FIXTURES
    Bathroom Group with 1.6 GPF Flushometer Valve 6.0 4.0
    Bathroom Group with 3.5 GPF (or higher) Flushometer Valve 8.0 6.0
    Kitchen Group with Sink and Dishwasher 2.0 1.5
    Laundry Group with Sink and Clothes Washer 5.0 3.0
    INDIVIDUAL FIXTURES
    Bar Sink 3/8" 1.0 0.5
    Bathtub or Combination Bath/Showcr 1/2" 4.0 3.5
    Bidet 1/2" 1.0 0.5
    Clothes Washer, Domestic 1/2" 4.0 2.5 4.0
    Dishwasher, Domestic 1/2" 1.5 1.0 1.5
    Drinking Fountain or Water Cooler 3/8" 0.5 0.75
    Hose Bibb (first) 1/2" 2.5 2.5 2.5
    Hose Bibb (each additional) 1/2" 1.0 1.0 1.0
    Kitchen Sink, Domestic 1/2" 1.5 1.0 1.5
    Laundry Sink 1/2" 2.0 1.0 2.0
    Lavatory 3/8" 1.0 0.5 1.0 1.0
    Service Sink or Mop Basin 1/2" 3.0
    Shower 1/2" 2.0 2.0 2.0
    Shower, continuous use 1/2" 5.0
    Urinal, 1.0 GPF 3/4" 4.0 5.0
    Urinal, greater than 1.0 GPF 3/4" 5.0 6.0
    Wash Fountain (per rated user) 0.5
    Wash Sink (1 or 2 faucets, per faucet) 1.0
    Wash Sink (additional faucets, per faucet) 0.5
    Water Closet, 1.6 GPF Gravity Tank 1/2" 2.5 2.5 2.5 4.0
    Water Closet, 1.6 GPF Flushometer Tank 1/2" 2.5 2.5 2.5 3.5
    Water Closet, 1.6 GPF Flushometer Valve 1" 5.0 5.0 5.0 8.0
    Water Closet, 3.5 GPF Gravity Tank 1/2" 3.0 3.0 5.5 7.0
    Water Closet, 3.5 GPF Flushometer Valve 1" 7.0 7.0 8.0 10.0
    Whirlpool Bath or Combination Bath/Showcr 1/2" 4.0 4.0
    NOTES FOR TABLE 10.14.2A:
    1. A Bathroom Group, for the purposes of this Table, consists of not more than one water closet, up to two lavatories, and either one bathtub, one bath/shower combination, or one shower stall. Other fixtures within the bathing facility shall be counted separately to determine the total water supply fixture unit load.
    2. A Half-Bath or Powder Room, for the purposes of this Table, consists of one water closet and one lavatory.
    3. For unlisted fixtures, refer to a listed fixture having a similar flow and frequency of use.
    4. The listed fixture unit values for Bathroom Groups and Individual Fixtures represent their load on the cold water service. The separate cold water and hot water fixture unit values for fixtures having both cold and hot water connections shall each be taken as 3/4 of the listed total value for the individual fixture.
    5. When WSFU values are added to determine the demand on the water distribution system or portions thereof, round the sum to the nearest whole number before referring to Table 10.14.2B for the corresponding gallons per minute (gpm) flow. WSFU values of 0.5 or more should be rounded up to the next higher whole number (9.5 = 10 WSFU). Values of 0.4 or less should be rounded down to the next lower whole number (9.4 = 9 WSFU).
    6. The listed minimum supply branch pipe sizes for individual fixtures are the nominal (I.D.) pipe size in inches.
    7. "Other Than Dwelling Units" applies to business, commercial, industrial, and assembly occupancies other than those defined under "Heavy-Use Assembly." Included are the public and common areas in hotels, motels and multi-dwelling buildings.
    8. "Heavy-Use Assembly" applies to toilet facilities in occupancies that place heavy, but intermittent, time-based demands on the water supply system, such as schools, auditoriums, stadiums, race courses, transportation terminals, theaters, and similar occupancies where queuing is likely to occur during periods of peak use.
    9. For fixtures or supply connections likely to impose continuous flow demands, determine their required flow in gallons per minute (gpm) and add it separately to the demand (in gpm) for the distribution system or portion thereof.
      Table 10.14.2B
      TABLE FOR CONVERTING DEMAND IN WSFU TO GPM1
      WSFU GPM Flush Tanks2 GPM Flush Valves3 WSFU GPM Flush Tanks2 GPM Flush Valves3
      3 3 120 49 74
      4 4 140 53 78
      5 4.5 22 160 57 83
      6 5 23 180 61 87
      7 6 24 200 65 91
      8 7 25 225 70 95
      9 7.5 26 250 75 100
      10 8 27 300 85 110
      11 8.5 28 400 105 125
      12 9 29 500 125 140
      13 10 29.5 750 170 175
      14 10.5 30 1000 210 210
      15 11 31 1250 240 240
      16 12 32 1500 270 270
      17 12.5 33 1750 300 300
      18 13 33.5 2000 325 325
      19 13.5 34 2500 380 380
      20 14 35 3000 435 435
      25 17 38 4000 525 525
      30 20 41 5000 600 600
      40 25 47 6000 650 650
      50 29 51 7000 700 700
      60 33 55 8000 730 730
      80 39 62 9000 760 760
      100 44 68 10,000 790 790
      NOTES FOR TABLE 10.14.2B:
      1. This table converts water supply demands in water supply fixture units (WSFU) to required water flow in gallons per minute (GPM) for the purpose of pipe sizing.
      2. This column applies to portions of piping systems where the water closets are the flush tank type (gravity or pressure) or there are no water closets, and to hot water piping.
      3. This column applies to portions of piping systems where the water closets are the flush valve type.
      4. Refer to Appendix K for WSFU values that are interpolated between the values listed in Table 10.14.2B to the degree that the WSFU increments are close enough that they do not produce GPM differences that would be significant in sizing water supply distribution piping.
10.14.3 Sizing Water Distribution Piping
  1. The supply demand in gallons per minute in the building hot and cold water distribution system shall be determined on the basis of the load in terms of water supply fixture units (WSFU) as shown in Table 10.14.2A and the relationship between the load in WSFU and the supply demand in gallons per minute (GPM) as shown in Table 10.14.2B. Refer to Appendix M for a more detailed table of WSFU and equivalent GPM. For fixtures having both hot water and cold water connections, the separate hot and cold water loads shall be taken as 75% of the listed WSFU value.
  2. Main risers and branches of the water distribution system shall be sized based on the minimum available water pressure at the source, any elevation differences between the source and the fixtures, pressure losses in the distribution system, and the pressure (with flow) required at each connection to the fixture supply branches. See Section 10.14.2.
10.14.4 Inadequate Water Pressure
Whenever water pressure from the street main or other sources of supply is insufficient to provide flow pressures at fixture outlets as required under Section 10.14.2, a booster pump and pressure tank or other approved means shall be installed on the building water supply system.
10.14.5 Variable Street Pressures
Where street water main pressures fluctuate, the building water distribution system shall be designed for the minimum pressure available.
10.14.6 Excessive Pressures
  1. Pressure reducing valves complying with ASSE 1003 shall be provided if required to limit the water supply pressure at any fixture, appliance, appurtenance, or outlet to not more than 80 psi under no-flow conditions.
  2. The requirement of Section 10.14.6.a above shall not prohibit supply pressures higher than 80 psi from water pressure booster systems under Section 10.14.4 or in high pressure distribution systems, provided that the pressure at the fixtures served is subsequently reduced to 80 psi maximum. Where operating water pressures exceed 80 psi, the working pressure rating of materials and equipment shall be suitable for the maximum pressure that may be encountered, including temporary increases or surges.
  3. Where pressure reducing valves are installed and the downstream piping is not rated for the maximum upstream pressure, a pressure relief valve shall be installed downstream from the pressure reducing valve. The relief valve shall be set not higher than the working pressure rating of the downstream piping and sized for not less than the flow capacity of the pressure reducing valve. Relief valves shall discharge in accordance with Section 10.16.6.
  4. When a pressure reducing valve is installed, a gauge port or pressure gauge with pressure range of 0-150 psi shall be installed within 24 inches downstream from the reducing valve.
EXCEPTION: In dwelling units, gauge ports or pressure gauges shall not be required if there is a hose bibb or hose-end drain valve to which a pressure test gauge can be connected.
See Figures 10.14.6-A and 10.14.6-B
Figure 10.14.6 - A
INSTALLATION OF A WATER PRESSURE REDUCING VALVE WHERE THE WATER SUPPLY PRESSURE EXCEEDS 80 PSIG
Figure 10.14.6 - B
ONE POSSIBLE ARRANGEMENT OF PRESSURE REDUCING VALVES IN A HIGH-RISE BUILDING
10.14.7 Water Hammer
  1. Approved water hammer arresters, complying with ASSE 1010 or PDI WH 201 shall be installed on water distribution piping in which quick closing valves are installed.
    EXCEPTION: Single lever faucets, domestic clothes washers, and domestic dishwashers.
  2. Water hammer arresters shall be placed as close as possible to the quick acting valve, at the end of long piping runs, or near batteries of fixtures.
  3. Arresters shall be accessible for replacement.
See Figure 10.14.7
Figure 10.14.7
WATER HAMMER ARRESTORS

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