1101.4
Material Uses. Pipe, tube, and fittings conveying rainwater shall
be of such materials and design as to perform their intended function to the
satisfaction of the authority having jurisdiction. Conductors within a vent or
shaft shall be of cast iron, galvanized steel, wrought iron, copper, copper
alloy, lead, Scheduled 40 ASB DWV, Scheduled 40 PVC DWV, stainless steel 304 or
316L (stainless steel 304 pipe and fittings shall not be installed underground
and shall be kept not less than six (6) inches (152 mm) aboveground), or other
approved materials, and changes in direction shall conform to the requirements
of Section 706.0. ABS and PVC DWV piping installations shall be installed in
accordance with IS 5 and IS 9. Except for individual single-family dwelling
units, materials exposed within ducts or plenums shall have a maximum
flame-spread index of 25 and a maximum smoke-developed index of 50, when tested
in accordance with ASTM E-84 and UL 723.
1101.12.2
Secondary Drainage.
Secondary (emergency) roof drainage shall be provided by one of the methods
specified in Section 1101.12.2.1 or Section 1101.12.2.2.
1101.12.2.1
Roof Scuppers or Open
Side. Secondary roof drainage shall be provided by an open-sided roof or
scuppers where the roof perimeter construction extends above the roof in such a
manner that water will be entrapped. An open-sided roof or scuppers shall be
sized to prevent the depth of ponding water from exceeding that for which the
roof was designed as determined by Section 1101.12.1. Scupper openings shall be
not less than four (4) inches (102 mm) high and have a width equal to the
circumference of the roof drain required for the area served, sized in
accordance with Table 1103.1, based on double the rainfall rate for the local
area.
EXCEPTION:
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Scupper openings shall be permitted to be sized for the
normal rainfall rate where the structural design of the roof includes a ponding
instability analysis in accordance with ASCE 7 for the additional ponding load
resulting from twice the normal rainfall rate or a 15-minute duration/100-year
return period storm. The analysis shall assume the primary drain system is
blocked.
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1101.12.2.2
Secondary Roof
Drain. Secondary roof drains shall be provided. The secondary roof
drains shall be located not less than two (2) inches (51 mm) above the roof
surface. The maximum height of the roof drains shall be a height to prevent the
depth of ponding water from exceeding that for which the roof was designed as
determined by Section 1101.12.1. The secondary roof drains shall connect to a
piping system in accordance with Section 1101.12.2.2.1 or Section
1101.12.2.2.2.
1101.12.2.2.1
Separate
Piping System. The secondary roof drainage system shall be a separate
system of piping, independent of the primary roof drainage system. The
discharge shall be above grade, in a location observable by the building
occupants or maintenance personnel. Secondary roof drain systems shall be sized
in accordance with Section 1101.12.1 based on double the rainfall rate for the
local area.
EXCEPTION:
|
The secondary drainage system shall be permitted to be
sized for the normal rainfall rate where the structural design of the roof
includes a ponding instability analysis in accordance with ASCE 7 for the
additional ponding load resulting from twice the normal rainfall rate or a
15-minute duration/100-year return period storm. The analysis shall assume the
primary drain system is blocked.
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1101.12.2.2.2
Combined System.
The secondary roof drains shall connect to the vertical piping of the primary
storm drainage conductor downstream of the last horizontal offset located below
the roof. The primary storm drainage system shall connect to the building storm
water that connects to an underground public storm sewer. The combined
secondary and primary roof drain systems shall be sized in accordance with
Section 1103.0 based on double the rainfall rate for the local area.
1101.13
Cleanouts. Cleanouts for building storm drains shall comply with
the requirements of this section.
1101.13.1
Locations. Rain leaders and conductors connected to a building
storm sewer shall have a cleanout installed at the base of the outside leader
or outside conductor before it connects to the horizontal drain. Cleanouts
shall be placed inside the building near the connection between the building
drain and the building sewer or installed outside the building at the lower end
of the building drain and extended to grade.
1101.13.2
Cleaning. Each
cleanout shall be installed so that it opens to allow cleaning in the direction
of flow of the soil or waste or at right angles thereto, and except in the case
of wye branch and end-of-line cleanouts, shall be installed vertically above
the flow line of the pipe.
1101.13.3
Access. Cleanouts
installed under concrete or asphalt paving shall be made accessible by yard
boxes, or extending flush with paving with approved materials and be adequately
protected.
1101.13.4
Manholes. Approved manholes may be installed in lieu of cleanouts
when first approved by the authority having jurisdiction.
The maximum distance between manholes shall not exceed three
hundred (300) feet (91.4 m).
The inlet and outlet connections shall be made by the use of a
flexible compression joint no closer than twelve (12) inches (305 mm) to, and
not farther than three (3) feet (914 mm) from the manhole. No flexible
compression joints shall be embedded in the manhole base.
1103.0
Size of
Leaders, Conductors, and Storm Drains.
1103.1
Vertical Conductors and
Leaders. Vertical conductors and leaders shall be sized by the maximum
projected roof area and Table 1103.1. Vertical conductors and leaders for
secondary roof drains shall be sized based on double the rainfall rate for the
local area.
EXCEPTION:
|
Vertical conductors and leaders for secondary drainage
systems shall be permitted to be sized for the normal rainfall rate where the
structural design of the roof includes a ponding instability analysis in
accordance with ASCE 7 for the additional ponding load resulting from twice the
normal rainfall rate or a 15-minute duration/100-year return period storm. The
analysis shall assume the primary drain system is blocked.
|
1103.2
Size of Horizontal Storm Drains and Sewers. The size of building
storm drains, or building storm sewers or their horizontal branches shall be
based on the maximum projected roof or paved area to be handled and Table
1103.2. Building storm drains, building storm sewers, or their horizontal
branches receiving drainage from secondary roof drain systems shall be sized
based on double the rainfall rate for the local area.
EXCEPTION:
|
Building storm drains, building storm sewers, or their
horizontal branches receiving drainage from secondary drainage systems shall be
permitted to be sized for the normal rainfall rate where the structural design
of the roof includes a ponding instability analysis in accordance with ASCE 7
for the additional ponding load resulting from twice the normal rainfall rate
or a 15-minute duration/100-year return period storm. The analysis shall assume
the primary drain system is blocked.
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1103.3
Size of Roof Gutters. The size of semi-circular gutters shall be
based on the maximum projected roof area and Table 1103.3.
1103.4
Side Walls Draining onto a
Roof. Where vertical walls project above a roof to permit storm water to
drain into the roof area below, the adjacent roof area shall be permitted to be
computed from Table 1103.1 as follows:
(1) (No
change to Items (1) through (7)) Secondary drainage systems for the adjacent
roof area shall be sized based on double the rainfall rate for the local area.
EXCEPTION:
|
Secondary drainage systems for the adjacent roof area
shall be permitted to be sized for the normal rainfall rate where the
structural design of the roof includes a ponding instability analysis in
accordance with ASCE 7 for the additional ponding load resulting from twice the
normal rainfall rate or a 15-minute duration/100-year return period storm. The
analysis shall assume the primary drain system is blocked.
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1105.0
Controlled-Flow Roof
Drainage. This section is not adopted.
Notes
Wash. Admin. Code
§
51-56-1100
Amended by
WSR
16-02-044, Filed 12/30/2015, effective
7/1/2016
Amended by
WSR
23-02-057, Filed 1/3/2023, effective
7/1/2023
Amended by
WSR
23-23-108, Filed 11/15/2023, effective
3/15/2024
Statutory Authority:
RCW
19.27.074,
19.27.031 and
chapters
19.27 and
34.05 RCW. 13-04-054, §
51-56-1100, filed 2/1/13, effective 7/1/13. Statutory Authority:
RCW
19.27.190,
19.27.020 and
chapters
19.27 and
34.05 RCW. 07-01-094, §
51-56-1100, filed 12/19/06, effective 7/1/07. Statutory Authority:
RCW
19.27.031 and
19.27.074. 04-01-110, §
51-56-1100, filed 12/17/03, effective
7/1/04.