Drainage Products Support - Helpful Tools and Resources
Grease Interceptor Sizing
To Determine the Flow Rate of Each Sink:
- Calculate the capacity of the sink in cubic inches:
___(length) x ___(width) x ___(depth) = ___cu. in.
- Convert the capacity from cubic inches to gallons per minute (GPM):
___ cu. in. / 231 = ___ GPM.
- Adjust for displacement:
___ GPM x 0.75 = ___ GPM.
- Result is the flow rate required to drain the sink in one minute.*
*Note: If drain down time is not critical, an interceptor with a lesser flow rate up to 1/2 the calculated flow rate may be specified.
Three compartment pot sink, each compartment 12" x 12" x 15"
- 12" x 12" x 15" = 2160 cu. in. x 3 comp. = 6480 cu. in.
- 6480 cu. in. / 231 = 28 GPM.
- 28 GPM x .75 = 21 GPM.
A 20 GPM interceptor would permit the sink to drain in slightly more than one minute.
*Discharge from spray hoods is determined by the flow rate of the hood.
*It is not recommended to pass commercial dishwashers through an interceptor.
Sizing For Multiple Fixtures
- Determine the flow rate for each fixture to be serviced by the interceptor.
- Add together 100% of the largest flow rate, 50% of the second largest, and 25% of all others.
- Result is the recommended flow rate of the interceptor.
- Fixture A: 35 GPM Flow Rate
Fixture B: 26 GPM Flow Rate
Fixture C: 18 GPM Flow Rate
Fixture D: 12 GPM Flow Rate
- 35 GPM (A) x 100% = 35 GPM
26 GPM (B) x 50% = 13 GPM
30 GPM (C + D) x 25% = 7.5 GPM
Total Flow Rate :55.5 GPM
A 50 GPM interceptor is recommended for this installation.