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Types, Sizing, Application and Maintenance A Brief Overview

This overview provides information about grease interceptors, including different types, how to size them, their application, and maintenance. It also clarifies the nomenclature between traps and interceptors.

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Types, Sizing, Application and Maintenance A Brief Overview

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  1. GREASE INTERCEPTORS Types, Sizing, Application and Maintenance A Brief Overview Presented by Max Weiss, Consultant Jay R. Smith Mfg. Co., Inc.

  2. Grease Interceptors - A Brief Overview Nomenclature: Traps vs. Interceptors 1 Interceptor Subtypes 2-6 Hydromechanical Grease Interceptors (GIs) Grease Recovery Devices (GRDs) Fats, Oils and Grease (FOG) Disposal Systems Gravity Grease Interceptors Sizing 7-11 Hydromechanical GIs – based on pipe size Gravity GIs – based on pipe size Hydromechanical GIs – based on fixture capacity Gravity GIs – based on fixture capacity Application 12 Maintenance 13-23 Pros/Cons by Type Conclusion 24

  3. Traps vs. Interceptors Nomenclature clarification ►Recent changes in codes and standards to clarify mixed terms ►“Trap” has been eliminated in ASME Standards, UPC, CSA and (pending) IPC ► “Interceptor” is deemed to be a more inclusive term ► “Interceptor” allows for a more precise distinction between devices ► First official adoption was by IAPMO during its comprehensive rewrite of Chapter Ten (10) of the Uniform Plumbing Code. 1

  4. Interceptor Subtypes Hydromechanical Grease Interceptors (GIs) Grease Recovery Devices (GRDs) Fats, Oils and Grease (FOG) Disposal Systems Gravity Grease Interceptors 2

  5. Hydromechanical GIs Definition Hydromechanical Grease Interceptor [Plumbing Drainage Institute] 3

  6. Grease Removal Devices Definition Grease Removal Device [Plumbing Drainage Institute] 4

  7. FOG Disposal Systems Definition FOG Disposal System [Plumbing Drainage Institute] 5

  8. Gravity Interceptors Definition Gravity Interceptor [Plumbing Drainage Institute] 6

  9. Interceptor Sizing UPC, Chapter 10, Appendix H Limitations Drainage Fixture Units [DFU] Misconception Maximum Flow Sizing Grease Interceptor Sizing Truths 7

  10. Hydromechanical Interceptor - based on pipe size Pipe Diameter Slope* GPM** Nominal Interceptor Rating 2.0 .120 13.75 15gpm .240 19.44 20gpm 3.0 .120 41.49 50gpm .240 58.67 75gpm 4.0 .120 88.93 100gpm .240 125.77 125gpm 5.0 .120 162.46 175gpm .240 229.75 250gpm 6.0 .120 265.50 275gpm .240 375.47 400gpm 8.0 .120 575.81 600gpm .240 814.32 825gpm * Inches drop per foot of run. **Based on Mannings formula with friction factor N=.012 as published by Cast Iron Soil Pipe Institute (CISPI) Or, actual fixture volume plus hydrant capacity, divided by drain period whichever is less. 8

  11. Gravity Interceptor - based on pipe size Pipe Diameter Slope* GPM** Nominal Interceptor Volume*** 2.0 .120 13.75 500 gal. .240 19.44 750 3.0 .120 41.49 1,250 .240 58.67 1,800 4.0 .120 88.93 2,750 .240 125.77 4,000 5.0 .120 162.46 5,000 .240 229.75 7,000 6.0 .120 265.50 8,000 .240 375.47 11,500 8.0 .120 575.81 18,000 .240 814.32 25,000 * Inches drop per foot of run. **Based on Mannings formula with friction factor N=.012 as published by Cast Iron Soil Pipe Institute (CISPI) ***Based on 30 min. retention (Metcalf & Eddy) rounded to nearest volume of 250 gal. increments. Or, actual fixture volume plus hydrant capacity, divided by drain period X 30 whichever is less. 9

  12. Hydromechanical Interceptor - based on fixture capacity Calculation of fixture capacity: [Length] X [Width] X [Depth] / [231] = Gallons X [.75 fill factor] / [Drain Period (1 or 2)] Add hydrant capacity (gpm supply); Add dishwasher, water wash hood at manufacturer ratings. EXAMPLE: The selection listed is based on application of the sizing formula above. 10

  13. Gravity Interceptor - based on fixture capacity Multiply the result of either "Fixture Capacity" or "Pipe Size" (above) by 30 to reflect required retention time. EXAMPLE 35 gpm X 30 = 1,050 gal. capacity. This sizing method is the "Uniform Interceptor Sizing“ – for obvious reasons. All parameters are uniformly applied to the computation of GPM from any given facility to any given interceptor. 11

  14. Application Why is an interceptor required? Pretreatmentas the prime consideration Administrative convenience versus concern for water quality Versatility of installation, proximity to FOG source, decreased maintenance frequency 12

  15. GI Maintenance Hydromechanical GIs Pros Located near the FOG source Usually small compared to gravity units Can be cleaned with conventional dip and bucket or small vacuum units Cons More convenient to ignore than to clean Will continue to flow water even after they no longer function as an interceptor Rarely have third party maintenance verification 13

  16. GI Maintenance Grease Removal Devices Pros Located near the FOG source Automatically remove FOG for proper disposal Less maintenance required Cons More expensive initially than hydromechanical GIs Require solids separation preceding the waste stream Have moving parts and are prone to mechanical problems 14

  17. GI Maintenance FOG Disposal Systems Pros Require less maintenance than GRDs – some requiring only annual service Can be quite small relative to the size flow capable of being treated Have the most rigorous performance testing and usually provide the cleanest effluent Remove solids with the use of a solids interceptor Cons More expensive than hydromechanical GIs and most GRDs Require attention to solids interceptors – neglect can affect performance of some units Frequently foreign to local jurisdictions 15

  18. GI Maintenance Gravity Interceptors Pros More recognized and usually easier to get approved by local authorities Require little or no attention from the facility operator Compatible with third party maintenance Cons Significantly more difficult and expensive to install The most frequently improperly sized interceptors The least efficient in terms of FOG separation Prone to hydrogen sulfide generation and accelerated corrosion Falsely believed to be capable of FOG storage exceeding 30 days Expensive to service at proper frequency and thoroughness 16

  19. GI Maintenance FOG in Lift Station 17

  20. GI Maintenance Corrosion Interior Concrete Interceptor 18

  21. GI Maintenance Other Lines in Lift Station 19

  22. GI Maintenance Combined Sewer Clogged with Grease 20

  23. GI Maintenance Grease in PVC Pipe 21

  24. GI Maintenance Channel in Grease Layer 22

  25. GI Maintenance Bag Type Interceptor 23

  26. Conclusion Rarely is the best interceptor for the job selected. Even more rarely is the selected interceptor sized correctly. Even rarer still is the interceptor that is installed correctly. Nonexistent is the interceptor that is the right interceptor for the job, sized properly, installed correctly AND operated and maintained as the manufacturer intended with the intent of producing the highest quality effluent possible. 24

  27. Thank you for your time!

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