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 1

Interceptor Subtypes 2-6Hydromechanical Grease Interceptors (GIs)Grease Recovery Devices (GRDs)Fats, Oils and Grease (FOG) Disposal SystemsGravity Grease Interceptors

Sizing 7-11Hydromechanical 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 13-23Pros/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.

1

Hydromechanical Grease Interceptors (GIs)

Grease Recovery Devices (GRDs)

Fats, Oils and Grease (FOG) Disposal Systems

Gravity Grease Interceptors

2

Definition

Hydromechanical Grease Interceptor [Plumbing Drainage Institute]

3

Definition

Grease Removal Device [Plumbing Drainage Institute]

4

Definition

FOG Disposal System [Plumbing Drainage Institute]

5

Definition

Gravity Interceptor [Plumbing Drainage Institute]

6

UPC, Chapter 10, Appendix H Limitations

Drainage Fixture Units [DFU] Misconception

Maximum Flow Sizing

Grease Interceptor Sizing Truths

7

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.

8

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.

9

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.

10

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.

11

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

12

Hydromechanical GIs

ProsLocated near the FOG source

Usually small compared to gravity units

Can be cleaned with conventional dip and bucket or small vacuum units

ConsMore 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

Grease Removal Devices

ProsLocated near the FOG source

Automatically remove FOG for proper disposal

Less maintenance required

ConsMore expensive initially than hydromechanical GIs

Require solids separation preceding the waste stream

Have moving parts and are prone to mechanical problems

14

FOG Disposal Systems

ProsRequire 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

ConsMore 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

Gravity Interceptors

ProsMore 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 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

17

FOG in Lift Station

18

Corrosion Interior Concrete Interceptor

19

Other Lines in Lift Station

20

Combined Sewer Clogged with Grease

21

Grease in PVC Pipe

22

Channel in Grease Layer

23

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.

24