Product Brochure

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Sizing by Capacity
Capacity: Based on the volume of wastewater discharge (gallons) into the interceptor expressed as discharge xture units
(DFU’s). DFU’s are identied in the currently published issue of Uniform Plumbing Code Ch.7 based on occupancy or use.
International Plumbing Code (IPC) also references/uses DFU’s
Note: Capacity sizing is typically applied to gravity grease interceptors (GGI) resulting in a liquid capacity that is substantially greater
than an equivalent hydromechanical GI. An HGI due to its qualied eciency and grease capacity at breakdown (when eciency
falls below 90%) results in actual grease capacity that is operationally equivalent to a GGI that is 5-6 times that of the HGI.
Example: Commercial sink with food waste with 1-1/2” trap, plus mop sink and special purpose sink 2” trap. 3+3+3=9 (DFU)
Referencing table below 9 DFU will require 750 gallon min. interceptor volume.
Floor Drains & Floor Sinks: Take the volume of water produced by the number of hose bibs (ie 1.5-2.0 gpm per 3/4” faucet)
Drainage Fixture
Units
Interceptor Volume
(min.)
8 500
21 750
35 1000
90 1250
172 1500
216 2000
Fixture Fixture Units Public
Floor drain, non-emergency 2
Special purpose sink w/1-1/2” trap 3
Special purpose sink w/2” trap 4
Special purpose sink w/3” trap 6
Commercial sink w/food waste w/ 1-1/2” trap 3
Bar Sink 2
Mop Sink 3
Laundry Sink 2
Total DFU Int. Vol. USG HGI GPM HGI Conversion Factor HGI size
8 500 17 1.00 20
21 750 31 1.25 35
35 1000 50 1.50 50
90 1250 73 1.75 75
172 1500 100 2.00 100
216 2000 167 2.50 2x 100
307 2500 250 3.00
* 3x 100
342 3000 350 3.00
* 3x 100
How can I convert DFU to GPM?
* NOTE: BEYOND VOLUME OF 2500 USG HGI CONVERSION FACTOR BECOMES CONSTANT AT 3:00
The conversion of DFU (Discharge Fixture Units) to Flow Rate equivalent is not directly achievable by application of a standard
formula. As an experienced manufacturer in the Grease Management market, we have been able to identify and validate a
method of conversion that references accepted engineering data and applies the following approach. This method is oered as
a manufacturers recommended method of conversion to determine Hydromechanical Grease Interceptor equivalency, to a
respective Gravity Grease Interceptor volume where initially determined by total calculated DFU discharge.
Step 1: Determine the total DFU discharge by following applicable code-dened methods and using UPC Table 1014.3.6 as a basis.
The total DFU is used to identify the respective Gravity Interceptor volume (US Gallons).
Step 2: Multiply the selected volume by the respective factor, (See HGI Conversion Factor column above) dividing the result by
30 (min). 30 minutes is the typical retention time used as the basis of design for Gravity Grease Interceptor (GGI) volume.
Example: At 50DFU discharge, a 1250 gallon Gravity Grease Interceptor (GGI) is identied by the table.
Therefore, 1250 (USG) x 1.75 (Conversion Factor) = 2188USG. Now divide the 2188gallons by the 30 minute retention time and the
output is 72.9GPM. Using established practice, this number is rounded up to the next standard size of interceptor available and so
conversion of a 1250USG Gravity Grease Interceptor is considered to be a 75GPM Hydromechanical GI.