SCHIER GB-75 75 GPM Great Basin Indoor Outdoor Grease Interceptor Installation Guide

: June 9, 2024
: SCHIER

Table of Contents

SPECIAL PRECAUTIONS
GETTING TO KNOW THE GB-75
Installation
Documents / Resources

INSTALLATION GUIDE
GB-75 75 GPM
Great Basin™ Indoor/Outdoor Grease Interceptor

SPECIAL PRECAUTIONS

For Schier Grease Interceptor Installations – Failure to follow this guidance voids your warranty

WARNING! DO NOT AIR TEST UNIT OR RISER SYSTEM!
Doing so may result in property damage, personal injury or death.
CAUTION! Do not install this unit in any manner except as described in these instructions.

Installation Instructions
Installation instructions and additional components are included with the interceptor. Read all instructions prior to installation. This interceptor is intended to be installed by a licensed plumber in conformance with all local codes.

Install interceptor as close as possible to ﬁxtures being served
Provide at least 16″ clearance above unit for routine maintenance.

High Temperature Kitchen Water
If water is entering the interceptor at excessive temperature (over 150º F), a drain water tempering valve (DTV) and approved backflow prevention assembly must be installed. Most state and local plumbing codes prohibit water above 150º F being discharged into the sanitary sewer. Water above 150º F will weaken or deform PVC Schedule 40 pipe, poly drainage fixtures like interceptors and erode the coating of cast iron (leading to eventual failure).

ODOR ALERT!
Interceptor is not a sewer gas trap.
All upstream ﬁxtures must be trapped

ODOR ALERT!
Do not install air gap on outlet side of interceptor.

Fully Support Base of Unit
Install unit on solid, level surface in contact with the entire footprint of unit base

Support Inlet and Outlet Piping
For above grade installations ensure heavy inlet and outlet piping (such as cast iron or long runs) is properly supported or suspended during the entire installation process to prevent connection failure or damage to bulkhead fittings.

Suspended Installations
Design trapeze to support the wet weight of the unit. Do not partially support unit or suspend unit using metal U-channel to create a trapeze.

DO NOT USE CAST IRON COVERS IN ABOVE GRADE OR INDOOR INSTALLATIONS
Use composite cover C24BC for above grade installations

Secure Cover Adapters
Cover adapters must be secured to base units in above grade installations with increased head pressure conditions. Use cover adapter tie-down kit model ATD1.

High Water Table Installations
Interceptors and risers are not designed max water table height for to withstand water table height in excess direct burial of the top of the unit when buried (see figure). If it is possible for this to occur, install the interceptor and risers in a water-tight concrete vault or backfill with concrete or flowable fill (wet concrete and flowable backfill should be poured in stages to avoid crushing the interceptor). At risk areas include but are not limited to tidal surge areas, model AK1 anchor kit floodplains and areas that receive storm water. Great Basin TM models that are direct buried in high water table scenarios must be installed with an anchor kit.

Hydrostatic/ Pressure Slabs
When installed under a hydrostatic slab (slab designed to withstand upward lift, usually caused by hydrostatic pressure) interceptor must be enclosed in a watertight concrete vault.

DO NOT COMPACT BACKFILL MECHANICALLY
Compact by hand only

Below Grade Installation Slab Requirements
A concrete slab to ﬁnished grade with rebar is required when installing interceptor below grade.

Installations with Risers

Corrugated Riser Pipe Requirements
Riser adapter model CA2 must be used when installing interceptors using 24″ diameter corrugated pipe as a riser.
This will adequately embed the cover adapter in the concrete slab, preventing cover/cover adaptor failure under traffic rated loads.

GETTING TO KNOW THE GB-75

1. Pickable cast iron cover (standard)
2. Cover gasket
3. Safety Star® access restrictor
4. Safety Star® tether
5. Cover adapter
6. Cover adapter gasket assembly with upper and lower stainless steel band clamps
7. 4″ cleanout plug (x2)
8. Outlet bulkhead connection (optional) 4″
FPT (x2)| 9. Bulkhead connection gasket
10. Bulkhead connection retaining nut
11. Inlet diffuser cover (white)
12. Inlet diffuser
13. Inlet diffuser retaining nut
14. Inlet diffuser foot retaining nut
15. Inlet diffuser (foot)
16. Inlet bulkhead connection 4″ FPT
17. 4″ plain end ﬁtting (x2)
18. Composite cover bolts and washers (x4)| 19. Bolted composite cover (optional)
20. Air relief/visual access
21. Outlet diuser retaining nut
22. Outlet diuser
23. Outlet diuser foot retaining nut
24. Outlet diuser (foot)
25. Outlet bulkhead connection (standard)
4″ FPT
26. 7/16″ nut driver bit
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Installation

Test tank for water tightness
1a
Cap all connection points with 4″ cleanout plugs using pipe thread sealant or tape approved for use with plastics.
1b
Remove cover. For base unit testing ﬁll with water to just above the highest connection.
Inspect unit, connections and gaskets for leaks. Check water level at speciﬁc time intervals per local code.
1c
Have a Leak?
Call customer care at 913-951-3300 Hours 8am-5pm CST, M-F
Excavate Burial Pit
Excavate hole at least 12″ larger than interceptor on all sides and 6″ deeper than tank bottom. Lay a level bed of well-packed, crushed aggregate (approximately 3/4″ size rock or sand, with no ﬁnes) in the base of hole.
Set Up Outlet Diffuser and Install Cleanout Plugs
3a Choose outlet location.
3b Reposition outlet diffuser (side outlets only)
Remove safety star insert, leave tethered to unit. Unscrew diffuser retaining nut and remove outlet diffuser.
Unscrew diffuser foot retaining nut and remove outlet diffuser foot. Rotate diffuser toward chosen outlet, replace foot ensuring it will point to the back wall of the unit and hand tighten foot retaining nut. Insert diffuser into chosen outlet and hand tighten retaining nut.
3c Cap unused connections(all conﬁgurations)
Screw in provided 4″ cleanout plugs using pipe thread sealant or tape approved for use with plastics. Do not cap the inlet or outlet connections attached to the diffusers.
Install Inlet Diffuser Components
This unit is supplied with a white inlet diffuser cover to prevent the unit from swamping in high ﬂow/ increased head pressure conditions.
• If dimension “A” is 13 feet or less, the inlet diffuser cover is not needed, go to Step 5, Connect Piping.
• If dimension “A” is more than 13 feet, or a high ﬂow/increased head pressure condition exists, follow Steps below.
4a Install inlet diffuser cover
Remove Safety Star® insert and remove inlet diffuser cover from the parts bag. Slide inlet diffuser cover into top of inlet diffuser and rotate clockwise until cartridge drops onto the inlet diffuser cover retainer pins.
Continue rotating clockwise until pins are fully seated.
4b OPTIONAL: install extension handle
For easy inlet diffuser cover removal in deep burial installations, 1-1/2″ PVC SCH. 40 pipe may used as an extension handle. Before risers have been installed, cut pipe to length and attach to top of cover using PVC primer/cement.
Extension handle length should be about 12″ shorter than total riser height.
Connect Piping
5a Install plain end ﬁttings
Screw plain end ﬁttings (included) into bulkhead ﬁttings using pipe thread sealant or tape approved for use with plastics. 6″ connection types come pre- installed from the factory.
5b Connect interceptor to drain lines
Place unit into ﬁnal position and set level. Mechanically couple inlet and outlet drainage lines to unit. Do not solvent weld. Ensure all upstream ﬁxtures are trapped. Vent per local code. Installation of 2-way cleanout tees to grade (by others) is recommended for buried installations.
Wet or Air Test Piping Per Local Code
WARNING! DO NOT AIR TEST UNIT OR RISER SYSTEM!
Doing so may result in property damage, personal injury or death.
Have a Leak?
Call customer care at 913-951-3300 Hours 8am-5pm CST, M-F
7 Bring Covers Flush-to-Grade
The GB-75 is ready for burial depth of 40″ from ﬁnished grade to bottom of tank (or 13-1/2″ to centerline of inlet).
Deeper burials will require extending the cover adapters and possibly adding risers.
7a Measure dimension X to determine riser height needed. Riser Height Needed Required| Risers Required
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0″ – 4″| None (use adapter)

4″ – 34″| FCR2 (x1)
34″ – 64″| FCR2 (x2)
64″ – 94″| FCR2 (x3)

7b Install risers if required
7c Make ﬁnal cover adapter adjustments
Loosen the cover adapter upper band clamp using 7/16″ Nut Driver Bit. Adjust cover adapter heights as needed. Maintain a minimum 2-1/2″ insertion depth. Tighten upper band clamp to 5 -8 ft. lbs. of torque using 7/16″ nut driver Bit. If required, cover adapters may now be tilted up to 10º in any direction using gasket ﬂexibility.

Install Anti-Flotation Anchor Kit
If the installation location is in a high water table or at risk area (including but not limited to tidal surge areas, ﬂoodplains and areas that receive storm water) the GB-75 must be installed with Schier model AK1 anchor kit.
Backﬁll and Finished Grade
9a Backﬁll
Fill unit with water for stabilization and ﬂoat-out prevention. Backﬁll evenly around tank using crushed aggregate (approximately 3/4″ size rock or sand with no ﬁnes)or ﬂowable ﬁll. Do not compact backﬁll around unit.
9b Pour concrete slab to ﬁnished grade
Vehicular Traffic Areas:
Minimum 8″ thick concrete slab with rebar required. Thickness of concrete around covers to be determined by
specifying engineer. If traffic loading is required the concrete slab dimensions shown are for guideline purposes only. Concrete to be 28 day compressive strength to 4,000 PSI. Use No. 4 rebar (ø 1/2″) grade 60 steel per ASTM A615: connected with tie wire. Rebar to be 2-1/2″ from edge of concrete and spaced in a 12″ grid with 4″ spacing around access openings.
Pedestrian Traffic or Greenspace Areas:
Minimum 4″ thick concrete slab with rebar required.

LIFETIME GUARANTEED GREASE INTERCEPTORS
913-951-3300 | schierproducts.com
© Copyright 2022 Schier Products Company, 11/21/22

Documents / Resources

| SCHIER GB-75 75 GPM Great Basin Indoor Outdoor Grease Interceptor [pdf] Installation Guide
4045-001-02, GB-75, GB-75 75 GPM Great Basin Indoor Outdoor Grease Interceptor, 75 GPM Great Basin Indoor Outdoor Grease Interceptor, Great Basin Indoor Outdoor Grease Interceptor, Indoor Outdoor Grease Interceptor, Outdoor Grease Interceptor, Grease Interceptor
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