Louisiana Administrative Code
Title 51 - PUBLIC HEALTH-SANITARY CODE
Part XIV - Plumbing
Chapter 6 - Water Supply and Distribution
Section XIV-611 - Sizing of Water Distribution System

Universal Citation: LA Admin Code XIV-611

Current through Register Vol. 50, No. 3, March 20, 2024

A. Minimum Sizes. The sizing of the water distribution system shall conform to good engineering practice (e.g., see §1805, Appendix B of this code). See §611. C of this code for the minimum required size of fixture branches and individual manifold distribution lines. See §611. D of this code for the minimum required size of fixture supplies and §611. E of this code for the minimum pressure required at fixture outlets.

B. Calculation of Sizes. When required by the plumbing official, the sizing of the water distribution system shall be calculated by a registered mechanical engineer or other acceptable authority.

C. Size of Fixture Branches and Manifold Individual Distribution Lines. The minimum size of fixture branches or manifold individual distribution lines shall be in accordance with the following Table 611.

Table 611

Minimum Size of Fixture Branches and Individual Manifold Distribution Lines

Type of Fixture or Device

Fixture Branch Pipe Size (in.)

Individual Manifold Distribution Line Size (in.)

Bathtubs (60" x 32" and smaller)

1/2

1/2

Bathtubs (Larger than 60" x 32")

1/2

1/2

Combination Sink and Tray

1/2

1/2

Drinking Fountain

1/2

1/2

Dishwasher (Domestic)

1/2

1/2

Kitchen Sink, Residential

1/2

1/2

Kitchen Sink, Commercial

3/4

3/4

Lavatory

1/2

1/2

Laundry Tray 1, 2, or 3 Compartments

1/2

1/2 (1 Tray)

Wall Hydrants

1/2

1/2

Shower (Single Head)

1/2

1/2

Sinks (Service, Slop)

1/2

1/2

Sinks Flushing Rim

3/4

3/4

Urinal (Flush Tank)

1/2

1/2

Urinal (Direct Flush Valve)

3/4

3/4

Water Closet (Flushometer Valve Type)

1

1

Water Closet (Gravity or Flushometer Tank Type)

1/2

1/2

Hose Bibbs

1/2

1/2
1. For fixtures not listed in Table 611 of this code above, the minimum fixture branch or manifold individual distribution line may be made the same as for a comparable fixture.

D. Size of Fixture Supply. The fixture supply piping, tubing, or flexible connector shall be sized in accordance with the fixture manufacturer's recommendations but in no case shall the size interfere with the minimum fixture outlet discharge pressure requirements specified in §611. E of this code.

E. Minimum Pressure. Minimum fairly constant service pressure at the point of outlet discharge shall be not less than 8 psi (55.2 kPa) flowing for all fixtures except for direct flush valves, for which it shall be not less than 15 psi (103 kPa) flowing, and except where special equipment is used requiring higher pressure. In determining the minimum pressure, allowance shall be made for the pressure drop due to friction loss in the piping system during maximum demand periods as well as head, meter, and other losses in the system.

F. Auxiliary Pressure, Supplementary Tanks. If the residual pressure in the system is below the minimum allowable at the highest water outlet when the flow in the system is at peak demand, an automatically controlled pressure tank or automatically controlled pump or gravity tank of sufficient capacity shall be installed. Its capacity shall be sufficient to supply sections of the building installation which are too high to be supplied directly from the water main.

G. Low Pressure Cutoff. When a booster pump is used on an auxiliary pressure system, there shall be installed a low-pressure (<15 psi gauge) cutoff on the booster pump to prevent the creation of negative pressures on the suction side of the water system. Other arrangements may be used if found adequate and if approved by the plumbing official.

1. Exception. In the case of fire pumps whose source of water is a potable water system, in lieu of a low-pressure cutoff, a low-suction throttling valve may be installed to sense the pressure in the water supply and automatically send a signal to a valve on the discharge side of the pump. This valve will not close all the way and it will not cutoff the fire pump, but it will modulate (open and close) to throttle back the discharge in an attempt to maintain a relatively constant pressure at the sensing location on the suction side of the pump. This allows the fire pump to keep sending water to the fire while the water supply pressure on the suction side of the pump recovers. Use of this valve protects against negative pressures being created in the potable water main when an uncontrolled fire pump is used. The valve body is to be located in between the pump discharge and discharge check valve with the sensing line connected to the suction side of the pump. The valve shall be set to prevent suction pressure from dropping below 15 psi.

H. Variable Street Pressures. When the street main has a wide fluctuation in pressure, the water distribution system shall be designed for minimum pressure available.

I. Hazard and Noise. Where water pressures are excessive or where required to eliminate water hammer or when deemed necessary by local authorities, approved engineered water hammer arresters or calculated air chambers shall be provided to safeguard the water distribution system against destructive water hammer hazard and noise.

1. Approved engineered mechanical water hammer arresters shall be sized and installed in accordance with PDI-WH201 or ASSE 1010. Where line water pressure exceeds 65 psi (448 kPa) in a water distribution system, the next larger size approved water hammer arrester shall be used. When water pressure exceeds 80 psi (552 kPa), a water pressure reducing valve shall be installed in accordance with §611. J of this code. Any approved engineered mechanical water hammer arrester shall have been tested by a recognized testing laboratory and certified to meet the requirements of the above standard.

2. Where calculated air chambers are installed, they shall be in an accessible place and each air chamber shall be provided with an accessible means for restoring the air in the event the chamber becomes waterlogged.

J. Water Pressure Reducing Valve or Regulators. The following shall apply relative to water pressure reducing valves or regulators.

1. Where water pressure within a building exceeds 80 psi (552 kPa) static, an approved water pressure regulator conforming to ASSE 1003 with strainer shall be installed to reduce the pressure in the building water distribution piping to 80 psi (552 kPa) static or less, whichever is consistent with good engineering practice. Exceptions to this requirement are service lines to sill cocks and outside hydrants, and main supply risers in tall buildings where pressure from the mains is reduced to 80 psi (552 kPa) or less at the fixture branches or at individual fixtures.

2. The delivery pressure variation shall not exceed 1 psi (6.895 kPa) for every 10 psi (69 kPa) pressure change in the inlet pressure. The reduced pressure fall-off from its no-flow setting shall not exceed 17 psi (117 kPa), and with a difference at this point of 50 psi (345 kPa) between the initial and this reduced flow pressure of 50 psi (345 kPa), the capacity shall be not less than that shown in Table 611.J of this code below.

Table 611.J

Minimum Capacity Based on Pipe Size

Nominal Pipe Size (in.)

1/2

3/4

1

1 1/4

1 1/2

2

Average velocity through pipe (ft/s)

10.5

10.0

9.5

9.0

8.5

7.5

Flow(gpm)

9.95

16.65

25.0

42.0

54.8

77.5

3. An integral bypass check valve shall be capable of opening to permit a reverse flow of water through the reducing valve to prevent a buildup of system pressure by thermal expansion of the water with an increase of reduced pressure not exceeding 2 psi (13.8 kPa) above the prevailing initial pressure.

4. The valve shall be designed to remain open to permit uninterrupted water flow in case of valve failure.

5. All regulators and strainers must be so constructed and installed as to permit repair or removal of parts without breaking a pipeline or removing the valve and strainer from the pipeline.

6. Approved valves shall comply with ASSE 1003.

K. Manifold Water Distribution Systems. Manifold water distribution systems shall comply with the following.

1. Hot water and cold water manifolds shall be sized according to Table 611.K of this code below.

Table 611.K

Maximum Gallons Per Minute (GPM) Available2

Nominal Size

ID (Inches)

Velocity1

4 fps

8 fps

1/2

2

5

3/4

6

11

1

10

20

1 1/4

15

31

1 1/2

22

44

NOTES:

1. For velocity limitations use manufacturers' recommendations.

2. Total gpm is the demand of all outlets.

2. Individual distribution pipe size shall conform to Table 611 of this code or to good engineering practice (e.g., see §1805, Appendix B of this code).

3. Individual fixture shutoff valves shall be installed at the outlet for each fixture. If secondary shutoff valves are used at the manifold, they shall be identified for the fixture being supplied.

4. Piping bundles for manifold systems shall be supported in accordance with Chapter 3. Direction changes and bending radiuses shall be in accordance with manufacturer's recommendations.

AUTHORITY NOTE: Promulgated in accordance with R.S. 40:4(A)(7) and R.S. 40:5(2)(3)(7)(9)(16)(17)(20).

Disclaimer: These regulations may not be the most recent version. Louisiana may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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