Types, Sizing, Application and Types, Sizing, Application and MaintenanceMaintenance

A Brief OverviewA Brief Overview

Presented by Max Weiss, ConsultantPresented by Max Weiss, Consultant Jay R. Smith Mfg. Co., Inc.Jay R. Smith Mfg. Co., Inc.

Nomenclature: Traps vs. Interceptors 1Interceptor Subtypes 2-6

Hydromechanical Grease Interceptors (GIs)Grease Recovery Devices (GRDs)Fats, Oils and Grease (FOG) Disposal SystemsGravity Grease Interceptors

Sizing 7-11Hydromechanical GIs – based on pipe sizeGravity GIs – based on pipe sizeHydromechanical GIs – based on fixture capacityGravity GIs – based on fixture capacity

Application 12Maintenance 13-23

Pros/Cons by Type

Conclusion 24

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.

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Hydromechanical Grease Interceptors (GIs)

Grease Recovery Devices (GRDs)

Fats, Oils and Grease (FOG) Disposal Systems

Gravity Grease Interceptors

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Definition

Hydromechanical Grease Interceptor [Plumbing Drainage Institute]

3

Definition

Grease Removal Device [Plumbing Drainage Institute]

4

Definition

FOG Disposal System [Plumbing Drainage Institute]

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Definition

Gravity Interceptor [Plumbing Drainage Institute]

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UPC, Chapter 10, Appendix H Limitations

Drainage Fixture Units [DFU] Misconception

Maximum Flow Sizing

Grease Interceptor Sizing Truths

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Pipe Diameter Slope* GPM** Nominal Interceptor Rating2.0 .120 13.75 15gpm

.240 19.44 20gpm3.0 .120 41.49 50gpm

.240 58.67 75gpm4.0 .120 88.93 100gpm

.240 125.77 125gpm5.0 .120 162.46 175gpm

.240 229.75 250gpm6.0 .120 265.50 275gpm

.240 375.47 400gpm8.0 .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.

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Pipe Diameter Slope* GPM** Nominal Interceptor Volume***2.0 .120 13.75 500 gal.

.240 19.44 7503.0 .120 41.49 1,250

.240 58.67 1,8004.0 .120 88.93 2,750

.240 125.77 4,0005.0 .120 162.46 5,000

.240 229.75 7,0006.0 .120 265.50 8,000

.240 375.47 11,5008.0 .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.

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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:Fixture Compartment Size,

in.

Compartments

Load,gal Recommended Interceptor Size,

One-Minute Drain

Two-Minute Drain

24x24x12 2 44.9 50 25

The selection listed is based on application of the sizing formula above.

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Multiply the result of either "Fixture Capacity" or "Pipe Size" (above) by 30 to reflect required retention time.

EXAMPLE35 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.

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Why is an interceptor required?

Pretreatment as the prime consideration

Administrative convenience versus concern for water

quality

Versatility of installation, proximity to FOG source,

decreased maintenance frequency

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Hydromechanical GIsPros

Located near the FOG source Usually small compared to gravity unitsCan be cleaned with conventional dip and bucket or small vacuum units

ConsMore convenient to ignore than to cleanWill continue to flow water even after they no longer function as an interceptorRarely have third party maintenance verification

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Grease Removal Devices

ProsLocated near the FOG source Automatically remove FOG for proper disposalLess maintenance required

ConsMore expensive initially than hydromechanical GIsRequire solids separation preceding the waste streamHave moving parts and are prone to mechanical problems

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FOG Disposal SystemsPros

Require less maintenance than GRDs – some requiring only annual serviceCan be quite small relative to the size flow capable of being treatedHave the most rigorous performance testing and usually provide the cleanest effluentRemove solids with the use of a solids interceptor

ConsMore expensive than hydromechanical GIs and most GRDsRequire attention to solids interceptors – neglect can affect performance of some unitsFrequently foreign to local jurisdictions

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Gravity InterceptorsPros

More recognized and usually easier to get approved by local authoritiesRequire little or no attention from the facility operatorCompatible with third party maintenance

ConsSignificantly more difficult and expensive to installThe most frequently improperly sized interceptorsThe least efficient in terms of FOG separationProne to hydrogen sulfide generation and accelerated corrosionFalsely believed to be capable of FOG storage exceeding 30 daysExpensive to service at proper frequency and thoroughness

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FOG in Lift Station

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Corrosion Interior Concrete Interceptor

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Other Lines in Lift Station

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Combined Sewer Clogged with Grease

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Grease in PVC Pipe

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Channel in Grease Layer

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Bag Type Interceptor

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.

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