|TRAP ARM PIPE DIAMETER |
|DISTANCE TRAP TO VENT MINIMUM |
|LENGTH MAXIMUM |
|Exceeding 4||2 × Diameter||120|
For SI units: 1 inch = 25.4 mm
1 Maintain 1/4 inch per foot slope (20.8 mm/m).
Exception: Drawn-copper alloy tubing traps shall not be used for urinals. Each trap shall have the manufacturer's name stamped legibly in the metal of the trap, and each tubing trap shall have the gauge of the tubing in addition to the manufacturer's name. A trap shall have a smooth and uniform interior waterway.
|DIAMETER OF GREASE WASTE PIPE |
|MAXIMUM FULL PIPE FLOW |
|SIZE OF GREASE INTERCEPTOR|
|ONE-MINUTE DRAINAGE PERIOD |
|TWO-MINUTE DRAINAGE PERIOD |
For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s
1 For interceptor sizing by the fixture capacity see the example below.
2 1/4 inch slope per foot (20.8 mm/m) based on Manning's formula with friction factor N = 012.
For this section, the term "fixture" shall mean and include each plumbing fixture, appliance, apparatus, or other equipment required to be connected to or discharged into a grease interceptor by a provision of this section.
Step 1: Determine the flow rate from each fixture.
[Length] X [Width] X [Depth] /  = Gallons X [.75 fill factor] / [Drain Period (1 minute or 2 minutes)]
Step 2: Calculate the total load from fixtures that discharge into the interceptor.
|SIZE OF GREASE INTERCEPTOR ONE-MINUTE DRAINAGE PERIOD |
|TWO-MINUTE DRAINAGE PERIOD |
|24 inches × 24 inches × 12 inches||2||44.9||—||—|
For SI units: 1 inch = 25.4 mm, 1 gallon per minute = 0.06 L/s, 1 gallon = 3.785 L
|DRAINAGE FIXTURE UNITS1, 3 |
|INTERCEPTOR VOLUME2 |
For SI units: 1 gallon = 3.785 L
2 This size is based on DFUs, the pipe size from this code; Table 703.2; Useful Tables for flow in half-full pipes (ref: Mohinder Nayyar Piping Handbook, 3rd Edition, 1992). Based on 30-minute retention time (ref.: George Tchobanoglous and Metcalf & Eddy. Wastewater Engineering Treatment, Disposal, and Reuse, 3rd Ed. 1991 & Ronald Crites and George Tchobanoglous. Small and Decentralized Wastewater Management Systems, 1998). Rounded up to nominal interceptor volume.
3 Where the flow rate of directly connected fixture(s) or appliance(s) have no assigned DFU values, the additional grease interceptor volume shall be based on the known flow rate (gpm) (L/s) multiplied by 30 minutes.
GRAVITY GREASE INTERCEPTOR SIZING EXAMPLE
Given: A restaurant with the following fixtures and equipment.
|3 floor drains at 2 DFUs each||=||6 DFUs|
|Mop sink at 3 DFUs each||=||3 DFUs|
|Food prep sink at 3 DFUs each||=||3 DFUs|
Using Table 1014.3.6, the grease interceptor will be sized at 750 gallons (2389 L).
For each 5 gpm (0.3 L/s) flow or fraction thereof over 20 gpm (1.26 L/s), the area of the sand interceptor inlet section is to be increased by 1 square foot (0.09 m2). The outlet section shall at all times have a minimum area of 50 percent of the inlet section.
The outlet section shall be covered by a solid removable cover, set flush with the finished floor, and the inlet section shall have an open grating, set flush with the finished floor and suitable for the traffic in the area in which it is located.
Interceptors not rated by the manufacturer shall have a depth of not less than 2 feet (610 mm) below the invert of the discharge drain. The outlet opening shall have not less than an 18 inch (457 mm) water seal and shall have a minimum capacity as follows: Where not more than three motor vehicles are serviced, stored, or both, interceptors shall have a minimum capacity of 6 cubic feet (0.2 m3), and 1 cubic foot (0.03 m3) of capacity shall be added for each vehicle up to 10 vehicles. Above 10 vehicles, the Authority Having Jurisdiction shall determine the size of the interceptor required. Where vehicles are serviced and not stored, interceptor capacity shall be based on a net capacity of 1 cubic foot (0.03 m3) for each 100 square feet (9.29 m2) of the surface to be drained into the interceptor, with a minimum of 6 cubic feet (0.2 m3).