Washington Administrative Code › Title 51 - Enterprise Services, Department of (Building Code Council) › Chapter 51-56 - State Building Code adoption and amendment of the 2021 edition of the Uniform Plumbing Code › Section 51-56-1100 - Chapter 11-Storm drainage

Current through Register Vol. 24-14, July 15, 2024
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:
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.
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.
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.