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916.3 Vent installation below the fixture flood level rim.
The vent located below the flood level rim of the fixture being vented shall be installed as required for drainage piping in accordance with Chapter 7, except for sizing. The vent shall be sized in accordance with Section 906.2. The lowest point of the island fixture vent shall connect full size to the drainage system. The connection shall be to a vertical drain pipe or to the top half of a horizontal drain pipe. Cleanouts shall be provided in the island fixture vent to permit rodding of all vent piping located below the flood level rim of the fixtures. Rodding in both directions shall be permitted through a cleanout.
919.1 General
Engineered vent systems shall comply with this section and Section 28-113.2.2 of the Administrative Code.
919.2 Individual branch fixture and individual fixture header vents.
The maximum developed length of individual fixture vents to vent branches and vent headers shall be determined in accordance with Table 919.2 for the minimum pipe diameters at the indicated vent airflow rates.
The individual vent airflow rate shall be determined in accordance with the following:
Qh,b = Nn,bQv (Equation 9-1)
For SI: Qh,b = Nn,bQv(0.4719 L/s)
where:
Nn,b = Number of fixtures per header (or vent branch) ÷ total number of fixtures connected to vent stack.
Qh,b = Vent branch or vent header airflow rate (cfm).
Qv = Total vent stack airflow rate (cfm).
Qv(gpm) = 27.8rs2/3 (1 - rs)D8/3
Qv(cfm) = 0.134Qv (gpm)
where:
D = Drainage stack diameter (inches).
Qw = Design discharge load (gpm).
rs = Waste water flow area to total area.
= Qw / 27.8D8/3
Individual vent airflow rates are obtained by equally distributing Qh,b into one-half the total number of fixtures on the branch or header for more than two fixtures; for an odd number of total fixtures, decrease by one; for one fixture, apply the full value of Qh,b.
Individual vent developed length shall be increased by 20 percent of the distance from the vent stack to the fixture vent connection on the vent branch or header.
Diameter of Vent Pipe (inches) | Individual Vent Airflow Rate (cubic feet per minute) | |||||||||||||||||||
Maximum developed length of vent (feet) | ||||||||||||||||||||
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | |
Diameter of Vent Pipe (inches) | Individual Vent Airflow Rate (cubic feet per minute) | |||||||||||||||||||
Maximum developed length of vent (feet) | ||||||||||||||||||||
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | |
1/2 | 95 | 25 | 13 | 8 | 5 | 4 | 3 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
3/4 | 100 | 88 | 47 | 30 | 20 | 15 | 10 | 9 | 7 | 6 | 5 | 4 | 3 | 3 | 3 | 2 | 2 | 2 | 2 | 1 |
1 | — | — | 100 | 94 | 65 | 48 | 37 | 29 | 24 | 20 | 17 | 14 | 12 | 11 | 9 | 8 | 7 | 7 | 6 | 6 |
1 1/4 | — | — | — | — | — | — | — | 100 | 87 | 73 | 62 | 53 | 46 | 40 | 36 | 32 | 29 | 26 | 23 | 21 |
1 1/2 | — | — | — | — | — | — | — | — | — | — | — | 100 | 96 | 84 | 75 | 65 | 60 | 54 | 49 | 45 |
2 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 100 |
For SI: 1 inch = 25.4 mm, 1 cubic foot per minute = 0.4719 L/s, 1 foot = 304.8 mm
919.3 A Licensed Professional Engineer shall certify design.
An engineer shall also inspect and certify the system upon completion of the system.
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