A
|
Flow from 4 or fewer kitchen fixtures enters the grease trap.
|
B
|
An approved flow-control device is installed to restrict the
flow to the grease trap to the rated capacity of the trap. Required
by the Collier Township Municipal Authority ("Authority").
|
C
|
An air intake valve allows air into the open space of the grease
trap to prevent siphonage and back-pressure.
|
D
|
The baffles help to retain grease toward the upstream end of
the grease trap, since grease floats and will generally not go under
the baffle. This helps to prevent grease from leaving the grease trap
and moving further downstream where it can cause blockage problems.
|
E
|
Solids in the wastewater that do not float will be deposited
on the bottom of the grease trap and will need to be removed during
trap cleaning.
|
F
|
Oil and grease floats on the water surface and accumulates behind
the baffles. The oil and grease will be removed during routine grease
trap cleaning.
|
G
|
Air relief is provided to maintain proper air circulation within
the grease trap.
|
H
|
Some grease traps have a sample point at the outlet end of the
trap to sample the quality of the grease trap effluent flow. Required
by the Authority.
|
I
|
A cleanout is provided at the outlet or just downstream of the
outlet to provide access into the pipe to remove any blockages.
|
J
|
The water exits the grease trap through the outlet pipe and
continues on to the grease interceptor or to the sanitary sewer system.
|
A
|
Flow from under-sink grease traps or directly from plumbing
fixtures enters the grease interceptor. The Authority requires that
all flow entering the interceptor must enter through the inlet pipe.
|
B
|
An approved flow-control or -restricting device is installed
to restrict the flow to the grease interceptor to the rated capacity
of the interceptor.
|
C
|
An air intake valve allows air into the open space of the grease
interceptor to prevent siphonage and back-pressure.
|
D
|
Oil and grease floats on the water surface and accumulates behind
the grease-retaining fittings and the wall separating the compartments.
The oil and grease will be removed during routine grease interceptor
cleaning.
|
E
|
Solids in the wastewater that do not float will be deposited
on the bottom of the grease interceptor and will need to be removed
during routine grease interceptor cleaning.
|
F
|
Grease-retaining fittings extend down into the water to within
12 inches of the bottom of the grease interceptor. Because grease
floats, it generally does not enter the fitting and is not carried
into the next compartment. The fittings also extend above the water
surface to provide air relief.
|
G
|
Some grease interceptors have a sample box so that inspectors
or employees of the establishment can periodically take effluent samples.
Having a sample box is required in all new installations by the Authority.
|
H
|
Flow exits the grease interceptor through the outlet pipe to
the sanitary sewer system.
|
_____ (Length) x _____ (Width) x _____ (Depth) = ____ Cu. In.
|
_____ Cu. In. x 231 Cu. In./Gal. = _____ GPM
|
_____ GPM x 0.75 = _____ GPM
|
Example:
| |
Three-compartment pot sink, with each compartment 12" x 12"
x 15"
| |
1.
|
12" x 12" x 15" = 2,160 Cu. In. x 3 Comp. = 6,480 Cu. In.
|
2.
|
6,480 Cu. In. ÷ 231 Cu. In./Gal. = 28 GPM
|
3.
|
28 GPM x 0.75 = 21 GPM
|
A 20 GPM grease trap 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.
|
Example:
| |
1.
|
Fixture A: 35 GPM flow rate
Fixture B: 26 GPM flow rate
Fixture C: 18 GPM flow rate
Fixture D: 12 GPM flow rate
|
2.
|
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
|
In this case, a 50 GPM outside grease interceptor is recommended
for this installation.
|
*
|
The Authority requires a minimum 22.5 GPM interior grease trap.
|
+
|
Automatic dishwashers must bypass interior grease traps.
|
++
|
Food waste grinders, disposals and potato peelers must be connected
to a solids interceptor then go to the sanitary sewer in this type
of installation.
|
Manufacture #1
| |
---|---|
Step 1 — Determine the Hydraulic Loading of Each Fixture,
in Fixture Units (FU)
| |
1.
|
Dishwasher receptor (floor sink) with 4" trap and trap arm =
8 FU
|
2.
|
Grease-extracting ventilation hood receptor (2" floor sink)
= 3 FU
|
3.
|
Tilt kettle trough (minimum 2" trap and trap arm) = 4 FU. Mop
sink = 3 FU
|
4.
|
Three-compartment (commercial) sink = 3 FU
|
5.
|
Prerinse sink with garbage disposal (2" trap and trap arm) =
4 FU
|
6.
|
Four floor drains x 2 FU each = 8 FU
|
Step 2 — Establish the Total Hydraulic Loading on the
Interceptor in Fixture Units
| |
8FU + 3FU + 4FU + 3FU + 4 FU + 8FU = 30 Fixture Units
| |
Step 3 — Determine the Minimum Size Interceptor Required
in Gallons
| |
The twenty-four-minute retention time applies to all fixtures
even though all fixtures may not discharge simultaneously.
| |
30 (FU) x 3 (GPM) x 24 (Minutes) Retention Time = 2,160 Gallons
| |
Solution: Choose the next larger available size three-compartment
interceptor (i.e., 2,500- or 3,000-gallon capacity)
|
Manufacture #2
| ||
---|---|---|
Kind of Fixture
|
Trap and Arm Size
|
Fixture Units
|
3-Compartment Sink
|
1 1/2", 2"
|
3, 4
|
2-Compartment Sink
|
1 1/2"
|
2
|
Dishwasher
|
2"
|
4
|
Garbage Grinder
|
1 1/2"
|
2
|
Wok Stove
|
2"
|
4
|
Hand Sink
|
—
|
0
|
Mop Sink
|
—
|
0
|
Floor Drains (2", 3", 4")
|
2", 3", 4"
|
2, 3, 4
|
Floor Sinks (3", 4")
|
3", 4"
|
3, 4
|
Notes: Hand sinks and mop sinks are not required to be plumbed
to the grease trap. For indirect waste systems where hub drains and
floor sinks are used as receptors for dishwashers, 2- and 3-compartment
sinks, etc., the fixture unit count shall be twice (2x) the floor
sink or hub drain fixture unit count. In such cases, the fixture count
of the indirect waste is not counted.
|
The Uniform Plumbing Code Formula
| ||||||
---|---|---|---|---|---|---|
Follow these six simple steps to determine grease interceptor
size.
| ||||||
Enter Calculations Here
|
No. of Meals Per Peak Hours
|
Waste Flow Rate
|
Retention Time
|
Storage Factor
|
Calculated Interceptor Size
|
Grease Interceptor
|
_____ x
|
_____ x
|
_____ x
|
_____ =
|
_____
|
_____
| |
Step 1
|
Step 2
|
Step 3
|
Step 4
|
Step 5
|
Step 6
|
Number of Meals per Peak Hour (Recommended Formula):
Seating Capacity x Meal Factor = Meals per Peak Hour
|
Notes:
| ||
1
|
Establishment Type:
Fast Food (45 min.)
Restaurant (60 min.)
Leisure Dining (90 min.)
Dinner Club (120 min.)
|
Meal Factor
1.33
1.00
0.67
0.50
| |
Waste Flow Rate:
| |||
2
|
Condition
With a Dishwashing Machine
Without a Dishwashing Machine
Single-Service Kitchen
Food Waste Disposer Only
|
Flow Rate
6 Gallons
5 Gallons
2 Gallons
1 Gallon
|
Notes:
|
Retention Time
| |||
3
|
Commercial Kitchen Waste
Dishwasher
Single-Service Kitchen
Single Serving
|
2.5 Hours
1.5 Hours
|
Notes:
|
Storage Factor
| |||
4
|
Kitchen Type — Commercial
Hours of Operation
8 Hours
12 Hours
16 Hours
24 Hours
Single-Service Kitchen
|
Storage Factor
1.00
1.50
2.00
3.00
1.50
|
Notes:
|
5
|
Calculate Liquid Capacity
Multiply the values obtained from Steps 1, 2, 3 and 4. The result
is the approximate grease interceptor size for this application.
|
Notes:
| |
6
|
Select Grease Interceptor
Using the approximate required liquid capacity from Step 5,
select an appropriate size as recommended by the manufacturer.
|
Notes:
|