Rainwater from roofs and storm water from paved areas, yards, courts and courtyards shall drain to an approvedplace of disposal. For one- and two-family dwellings, and where approved, storm water is permitted to discharge onto flat areas, such as streets or lawns, provided that the storm water flows away from the building.
All connections and changes in direction of the stormdrainage system shall be made with approveddrainage-type fittings in accordance with Table 706.3. The fittings shall not obstruct or retard flow in the system.
Roofs shall be designed for the maximum possible depth of water that will pond thereon as determined by the relative levels of roof deck and overflow weirs, scuppers, edges or serviceable drains in combination with the deflected structural elements. In determining the maximum possible depth of water, all primary roof drainage means shall be assumed to be blocked. The maximum possible depth of water on the roof shall include the height of the water required above the inlet of the secondary roof drainage means to achieve the required flow rate of the secondary drainage means to accommodate the design rainfall rate as required by Section 1106.
The materials and methods utilized for the construction and installation of stormdrainage systems shall comply with this section and the applicable provisions of Chapter 7.
Pipe fittings shall be approvedfor installation with the piping material installed, and shall conform to the respective pipe standards or one of the standards listed in Table 1102.7. The fittings shall not have ledges, shoulders or reductions capable of retarding or obstructing flow in the piping. Threaded drainage pipe fittings shall be of the recessed drainage type.
Roof drains shall be installed in accordance with the manufacturer's instructions. The inside opening for the roof drain shall not be obstructed by the roofing membrane material.
The size of the vertical conductors and leaders, building stormdrains, building stormsewersand any horizontal branches of such drains or sewersshall be based on the 100-year hourly rainfall rate indicated in Figure 1106.1 or on other rainfall rates determined from approvedlocal weather data.
For SI: 1 inch = 25.4 mm. Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington D.C.
FIGURE 1106.1 100-YEAR, 1-HOUR RAINFALL (INCHES) EASTERN UNITED STATES
For SI: 1 inch = 25.4 mm. Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington D.C.
FIGURE 1106.1—continued 100-YEAR, 1-HOUR RAINFALL (INCHES) CENTRAL UNITED STATE
For SI: 1 inch = 25.4 mm. Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington D.C.
FIGURE 1106.1—continued 100-YEAR, 1-HOUR RAINFALL (INCHES) WESTERN UNITED STATES
For SI: 1 inch = 25.4 mm. Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington D.C.
Vertical and horizontal stormdrainpiping shall be sized based on the flow rate through the roof drain. The flow rate in stormdrainpiping shall not exceed that specified in Table 1106.2.
Vertical leaders shall be sized based on the flow rate from horizontal gutters or the maximum flow rate through roof drains. The flow rate through vertical leaders shall not exceed that specified in Table 1106.3.
In sizing roof drains and stormdrainage piping, one-half of the area of any vertical wall that diverts rainwater to the roof shall be added to the projected roof area for inclusion in calculating the required size of vertical conductors, leaders and horizontal stormdrainage piping.
Horizontal gutters shall be sized based on the flow rate from the roof surface. The flow rate in horizontal gutters shall not exceed that specified in Table 1106.6.
Where roof drains are required, secondary (emergency overflow) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that water will be entrapped if the primary drains allow buildup for any reason. Where primary and secondary roof drains are manufactured as a single assembly, the inlet and outlet for each drain shall be independent.
Secondary roof drain systems shall have the end point of discharge separate from the primary system. Discharge shall be above grade, in a location that would normally be observed by the building occupants or maintenance personnel.
Secondary (emergency) roof drain systems shall be sized in accordance with Section 1106 based on the rainfall rate for which the primary system is sized. Scuppers shall be sized to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by Section 1101.7. Scuppers shall have an opening dimension of not less than 4 inches (102 mm). The flow through the primary system shall not be considered when sizing the secondary roof drain system.
The roof of a structure shall be designed for the storage of water where the stormdrainage system is engineered for controlled flow. The controlled flow roof drain system shall be an engineered system in accordance with this section and the design, submittal, approval, inspection and testing requirements of Section 316.1. The controlled flow system shall be designed based on the required rainfall rate in accordance with Section 1106.1.
The control devices shall be installed so that the rate of discharge of water per minute shall not exceed the values for continuous flow as indicated in Section 1110.1.
Not less than two roof drains shall be installed in roof areas 10,000 square feet (929 m2) or less and not less than four roof drains shall be installed in roofs over 10,000 square feet (929 m2) in area.
Subsoil drains shall be open-jointed, horizontally split or perforated pipe conforming to one of the standards listed in Table 1102.5. Such drains shall not be less than 4 inches (102 mm) in diameter. Where the building is subject to backwater, the subsoil drain shall be protected by an accessibly located backwater valve. Subsoil drains shall discharge to a trapped area drain, sump, dry well or approvedlocation above ground. The subsoil sump shall not be required to have either a gas-tight cover or a vent. The sump and pumping system shall comply with Section 1113.1.
Building subdrainslocated below the public sewerlevel shall discharge into a sump or receiving tank, the contents of which shall be automatically lifted and discharged into the drainage system as required for building sumps. The sump and pumping equipment shall comply with Section 1113.1.
The sump pit shall be not less than 18 inches (457 mm) in diameter and not less than 24 inches (610 mm) in depth, unless otherwise approved. The pit shall be accessible and located such that all drainage flows into the pit by gravity. The sump pit shall be constructed of tile, steel, plastic, cast iron, concrete or other approvedmaterial, with a removable cover adequate to support anticipated loads in the area of use. The pit floor shall be solid and provide permanent support for the pump.
Discharge piping shall meet the requirements of Section 1102.2, 1102.3 or 1102.4 and shall include a gate valve and a full flow check valve. Pipe and fittings shall be the same size as, or larger than, the pump discharge tapping.
Exception: In one- and two-family dwellings, only a check valve shall be required, located on the discharge piping from the pump or ejector.
