Materials
Refer to CPS Specifications for requirements.
Sizing
All storm piping shall be designed based on a rainfall rate of 4 in. per hour. Pipe sizing shall conform to the tables provided in the City of Chicago Plumbing Code.
Distribution
All storm piping shall be sloped for proper gravity drainage.
- Piping less than 4” diameter shall be sloped at ¼” per foot.
- Piping 4” diameter and greater shall be sloped at ⅛” per foot.
Cleanouts shall be installed at 50 feet on center for piping 4” and smaller, at 100 feet on center for piping 5” and larger, and at changes in direction of greater than 45 degrees, at the bottom of vertical risers and as the sewer exits the building. All horizontal storm piping and drain bodies shall be insulated.
Roof Drain Sizing
Combination type roof drains shall be provided at all roofs receiving rainfall. The maximum area per drain shall be 5,000 SF. A minimum of 2 roof drains shall be provided for roofs less than 10,000 SF. For a roof over 10,000 SF, a minimum of 4 drains shall be used. All roof drains shall be discharged to a catch basin located at least 10’-0” from the building.
Gutter Systems
If a gutter system is determined to be the best fit for a building, it shall be designed per City of Chicago Plumbing Code. Provide gutters with exterior downspouts for all pitched roof areas. Collect exterior downspouts underground and extend to site storm sewers or greywater collection system. Gutter systems shall be equipped with ice-melting systems. Discharge locations shall be fully coordinated with the Civil Engineer in order to allow for proper retention and to avoid discharge to an improper location that may cause a hazard or damage to the site.
Secondary Roof Drains
Secondary or emergency roof drainage shall be provided where the roof’s perimeter construction extends above the roof in such a manner that water will be entrapped in case the primary drain is blocked or allows buildup.
The secondary drain piping system shall be designed similarly to the primary drainage system, but these drains shall be installed separately from the primary system. A minimum of one roof drain from each roof area or level shall spill to grade via a lambs tongue spout.
For renovation projects only, a secondary roof drainage system may consist of either scepters through the sides of the building or separate roof drains installed at a higher elevation than the primary roof drain. If scuppers are utilized, they shall be placed 1/2 inch above the maximum designated head or 4 inches above the roof level. One scupper or secondary drain shall be provided for each roof drain. The structural engineer shall be advised that scuppers shall be installed to accommodate the additional weight of the water. Scuppers shall not be placed above window or door locations and shall drain into a permeable area with proper drainage slope.
Vegetated Roofs
As a rule, Vegetated Roofs are not a requirement for CPS projects. This requirement is substituted with Stormwater Management.
Greywater Collection Systems
A Greywater collection system may be used to offset water usage for some of the building systems. Additionally, if this system is to be used, it shall be approved in writing by authorized CPS administrative personnel. The most common uses for rainwater reuse are fixture flushing, irrigation and HVAC makeup water. Other uses may include vehicle washing, pool or water feature filling, or building washing.
A rainwater harvesting system involves several key components: a catchment surface, conveyance system, prefiltration system, collection cistern for storage, and treatment system. The treatment system at a minimum consists of pressurization pumps, recirculation pumps, filtration, sanitization, dye injection as required by local codes, and additional treatment depending on the quality of the water required at the point of use.
Storage tank size shall be calculated based on user demand, rainfall rate, roof area and runoff rate. Storage tanks shall be placed within the building or below grade to prevent winter freezing of the system. All rainwater shall be properly filtered, disinfected and injected with blue food dye, where applicable. All distribution piping for this system shall be piping painted purple and clearly labeled as non-potable.
Rodding/Jetting/Televising
Roof projects/major MEP renovation projects shall include rodding/jetting and televising documentation of each roof vent back to the main in the street. Documentation shall include a plan drawing to scale identifying each vent route with sizes, video and report narrative. On renovation projects this shall be performed three times. Once at the beginning of design to clear the lines/ determine the condition of the system (identify blockages, pinch points, missing cleanout/access points, pipe breaks, etc.) and establish repair scope. The second time at the beginning of construction as the conditions may have changed / additional scope may be needed and the third post construction to document the final installed fully functional system. Projects shall include post construction to document the final fully functional system. The EOR shall provide the Rodding/Jetting/Televising service during the design phase as a pass through expense. Copies of documentation, including narrative of findings, video, tagged site and floor plan to scale showing routing and pipe sizes, shall be turned over to CPS. On renovation projects this shall be performed three times. The first time is at the beginning of design to clear the lines/determine the condition of the system (identify blockages, pinch points, missing cleanup/access points, etc.) and establish repair scope. The second time is at the beginning of construction as the conditions may have changed/additional scope may be required. The third time is post construction to document the final installed fully functional system.