CPC · California Plumbing Code
Grease, oil, and solids interceptors — when required and referenced sizing/tables
If your building discharges grease, oil or heavy solids you may need an interceptor. The CPC requires approved interceptors and gives two sizing methods: hydromechanical devices sized by certified gpm (total fixture gallons must be ≤ 2.5× the interceptor’s gpm rating; **§ 1014.2.1**) and gravity interceptors sized by kitchen DFUs using **Table 1014.3.6**; AHJ approval and listed standards from **Table 1009.1** apply.
Last reviewed: July 6, 2026
What the code requires — plain English
The California Plumbing Code requires an interceptor (clarifier) when it is necessary to protect the building drainage system or sewer from grease, oil, sand, solids or other harmful wastes — see § 1009.1 .
Commercial kitchen grease control is regulated separately: hydromechanical grease interceptors must be sized so the total fixture capacity does not exceed two and one‑half times the certified gpm rating of the interceptor (the sizing reference is Table 1014.2.1 in § 1014.2.1) . Gravity grease interceptors are sized by DFUs using Table 1014.3.6 and must meet the construction/retention requirements in the gravity interceptor section .
Interceptors are required when needed to protect drains/sewers; hydromechanical interceptor capacity is limited to 2.5× the interceptor’s certified gpm rating per § 1014.2.1.
Requirements in detail
Key definitions (first mention bolded)
- Grease Interceptor — plumbing device to intercept non‑petroleum fats, oils and grease (FOG) from wastewater; (see definition and gravity interceptor characteristics) § 1014 .
- Hydromechanical Grease Interceptor (Type A/B) — GRD/Type A or Type B devices sized using gravity flow rates and certified gpm values; sizing referenced in § 1014.2.1 and Table 1014.2.1 .
- Gravity Grease Interceptor — volume‑based interceptor identified by 30‑minute retention time, not less than two compartments, and minimum total volume 300 gallons; sized by DFUs using Table 1014.3.6 .
Approved interceptor types & standards (from Table 1009.1)
| Application | Typical referenced standards | Code Reference |
|---|---|---|
| Fats, Oil, Grease (FOG) | ASME A112.14.3, ASME A112.14.4, ASME A112.14.6, CSA B481, ANSI/CAN/IAPMO Z1001, PDI G‑101, PDI G‑102 | Table 1009.1 / § 1009.1 |
| Solid waste interceptors | IAPMO IGC 167 | Table 1009.1 |
| Non‑petroleum oil separators | ASME A112.14.6, IAPMO PS 80, PDI G‑102 | Table 1009.1 |
| Petroleum oil separators | ASTM D6104, IAPMO IGC 183, IAPMO IGC 325 | Table 1009.1 |
(Authority Having Jurisdiction must approve size/type/location — § 1009.2.)
Hydromechanical grease interceptor sizing (Table 1014.2.1)
Short rule: the total gallons of the fixtures discharging into a hydromechanical interceptor shall not exceed 2.5 times the interceptor’s certified gpm rating (that relationship is the sizing control; see § 1014.2.1) .
Table (extracted decision‑relevant numbers from Table 1014.2.1):
| Diameter of grease waste pipe (in) | Max full‑pipe flow (gpm)2 | One‑minute drainage (gpm) | Two‑minute drainage (gpm) | Code Reference |
|---|---|---|---|---|
| 2 | 20 | 20 | 10 | Table 1014.2.1 / § 1014.2.1 |
| 3 | 60 | 75 | 35 | Table 1014.2.1 / § 1014.2.1 |
| 4 | 125 | 150 | 75 | Table 1014.2.1 / § 1014.2.1 |
| 5 | 230 | 250 | 125 | Table 1014.2.1 / § 1014.2.1 |
| 6 | 375 | 400 | 200 | Table 1014.2.1 / § 1014.2.1 |
Notes in the CPC: the table is calculated from gravity flow assumptions (1/4" per foot slope, Manning’s formula) and the one‑ or two‑minute drain periods are used when computing fixture volumes per the example method in § 1014.2.1 .
How to apply (summary):
- Compute the fixture volume (or use gravity flow rates from the table) during the chosen drain period (1 or 2 minutes). The code gives a worksheet method in the Example under § 1014.2.1 .
- Required interceptor certified gpm must be such that: Fixture total gallons ≤ 2.5 × (interceptor certified gpm). See § 1014.2.1 .
Gravity grease interceptor sizing (Table 1014.3.6)
Gravity interceptors are sized by Drainage Fixture Units (DFUs) on the kitchen drain line, using Table 1014.3.6. The table maps DFU totals to required interceptor volumes (gallons) based on a 30‑minute retention time. Example entries:
| DFUs (kitchen drain) | Interceptor volume (gallons) | Code Reference |
|---|---|---|
| 8 | 500 | Table 1014.3.6 / § 1014.3.6 |
| 21 | 750 | Table 1014.3.6 / § 1014.3.6 |
| 35 | 1000 | Table 1014.3.6 / § 1014.3.6 |
| 90 | 1250 | Table 1014.3.6 / § 1014.3.6 |
| ... | ... | Table 1014.3.6 |
Practical notes: if DFU values are unknown for a particular appliance, the CPC allows using the known gpm multiplied by 30 minutes to compute the required interceptor volume (see the Notes to Table 1014.3.6) .
Installation & operational requirements (high‑priority bullets)
- Fixtures discharging to grease interceptors must be individually trapped and vented — § 1014.1.1 .
- No toilets or urinals may drain through a grease interceptor — § 1014.3.2.1 .
- Hydromechanical interceptors require a vent downstream and a vented flow control at the inlet; flow control devices must be non‑adjustable and sized so total flow does not exceed the interceptor rating — § 1014.2 / § 1014.2.2 .
- Authority Having Jurisdiction approval is required for size/type/location and may mandate stricter maintenance or additional devices — § 1009.2, § 1014.1.2 .
Exceptions & special cases
- Food waste disposers and dishwashers: normally prohibited from discharging into grease interceptors, except listed food waste disposers specifically designed to discharge to a grease interceptor — § 1014.1.3 .
- Gravity interceptors complying with ANSI/CAN/IAPMO Z1001 are not to be installed inside a building where food is handled (OSHPD and AHJ constraints may apply) — § 1014.3.4 and § 1015.5 .
- The AHJ can require sand interceptors, oil interceptors, or alternative engineered systems where particular wastes exist (see § 1009.1, § 1016.2, § 1017.1) .
- Where DFUs are not assigned, use known gpm × 30 minutes to determine additional gravity interceptor volume (note to Table 1014.3.6) .
Common mistakes
- Installing an interceptor type that is not an approved standard from Table 1009.1 (e.g., using an unlisted device) — check Table 1009.1 and get AHJ approval § 1009.1/1009.2 .
- Forgetting the non‑adjustable vented flow control requirement at hydromechanical inlets (leads to oversizing or bypass risk) — see § 1014.2 .
- Routing toilets/urinals through grease interceptors (expressly prohibited) — § 1014.3.2.1 .
- Using food preparation area space for gravity interceptors that the code or AHJ prohibits (OSHPD and local rules apply) — § 1014.3.4 and § 1015.5 .
- Misreading DFU mapping to interceptor volume — always use Table 1014.3.6 or the table’s notes and round up to the nearest nominal interceptor size § 1014.3.6 .
Worked example — gravity interceptor (concrete)
Given: a restaurant kitchen with:
- Three floor drains (each 2 DFUs) = 6 DFUs
- One mop sink (3 DFUs) = 3 DFUs
- One food preparation sink (3 DFUs) = 3 DFUs
Total kitchen drain DFUs = 12 DFUs.
Using Table 1014.3.6 (DFU → interceptor volume), 12 DFUs falls between the 8 DFU → 500 gal and 21 DFU → 750 gal rows; the table/example in the CPC rounds up and selects 750 gallons for 12 DFUs in the example provided in § 1014.3.6 . This matches the CPC example (restaurant total = 12 DFUs → 750 gal interceptor) .
Worked example — hydromechanical interceptor (concrete)
Given: one sink with two compartments sized 24"×24"×12" each. Using the CPC example worksheet method (volume calc → fill factor → drain period), that dual‑compartment sink yields roughly 45–50 gallons of drain load (the code example shows ~44.9 gallons for comparable compartments). The example in the CPC then selects a hydromechanical interceptor sized for 50 gpm (one‑minute drain period) or 25 gpm (two‑minute) per Table 1014.2.1 and the example worksheet; the required certified gpm is selected so that total gallons ≤ 2.5 × certified gpm (see § 1014.2.1 and the example) .
Related provisions (quick list)
- § 1009.1 — Where interceptors are required (general)
- § 1009.2 — AHJ approval of size/type/location
- § 1014.1 — General grease interceptor rules (maintenance, applicability)
- § 1014.2 / § 1014.2.1 — Hydromechanical interceptors; capacity and Table 1014.2.1 sizing
- § 1014.3.6 — Gravity grease interceptor sizing (Table 1014.3.6)
- Table 1009.1 — Approved interceptors and referenced standards
- § 1015.5 / § 1015.6 — Location and installation restrictions (OSHPD contexts)
Code references
Grounded in the retrieved California Plumbing Code — click a citation to read the verbatim passage:
CPC § 1014.3.6 High relevance — show source text
Rounded up to nominal interceptor volume. 3 Where the flow rate of directly connected fixture(s) or appliance(s) have no assigned DFU values, the additional grease interceptor volume shall be based on the known flow rate (gpm) (L/s) multiplied by 30 minutes.
EXAMPLE 1014.3.6
GRAVITY GREASE INTERCEPTOR SIZING EXAMPLE
Given: A restaurant with the following fixtures and equip ment.
One food preparation sink; three-floor drains - one in the food prep area, one in the grill area, and one receiving the indirect waste from the ice machine and a mop sink.
Kitchen Drain Line DFU Count (from Table 702.1):
3 floor drains at 2 DFUs each = 6 DFUs
Mop sink at 3 DFUs each = 3 DFUs
Food prep sink at 3 DFUs each = 3 DFUs
Total = 12 DFUs
Using Table 1014.3.6, the grease interceptor will be sized at 750 gallons (2389 L).
1015.0 FOG (Fats, Oils, and Greases) Disposal Sys- tem.
1015.1 Purpose. The purpose of this section is to provide the necessary criteria for the sizing, application, and installation of FOG disposal systems designated as a pretreatment or discharge water quality compliance strategy.
TABLE 1014.3.6
GRAVITY GREASE INTERCEPTOR SIZING
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TRAPS AND INTERCEPTORS
1015.2 Components, Materials, and Equipment. FOG disposal systems, including components, materials, and equipment necessary for the proper function of the system, shall comply with ASME A112.14.6. 1015.3 Sizing and Installation. FOG disposal systems shall be sized and installed in accordance with the manufac turer’s installation instructions.
1015.4 Performance. FOG disposal systems shall produce an effluent quality not to exceed 5.84 grains per gallon (gr/gal) (100 mg/L) FOG. 1015.5 [OSHPD 1, 1R, 2, 3, 4 & 5] Grease interceptors shall not be installed in food preparation area of kitchens. 1015.6 [OSHPD 1, 1R, 2, 3, 4 & 5] Grease interceptors shall be installed outside of the kitchen area in location affording ease of maintenance and servicing.
1016.0 Sand Interceptors.
1016.1 Discharge. Where the discharge of a fixture or drain contains solids or semi-solids heavier than water that would be harmful to a drainage system or cause a stoppage within the system, the discharge shall be through a sand interceptor. Multiple floor drains shall be permitted to discharge into one sand interceptor. 1016.2 Authority Having Jurisdiction. Sand interceptors are required where the Authority Having Jurisdiction deems it advisable to have a sand interceptor to protect the drainage system. 1016.3 Construction and Size. Sand interceptors shall be built of brick or concrete, prefabricated coated steel, or other watertight material. The interceptor shall have an interior baffle for full separation of the interceptor into two sections.
CPC § 1009.1 High relevance — show source text
TABLE 1009.1 APPROVED INTERCEPTORS (CLARIFIERS)
APPLICATION STANDARD
Fats, Oil, Grease
(FOG)ASME A112.14.3, ASME A112.14.4,
ASME A112.14.6, CSA B481,
ANSI/CAN/IAPMO Z1001,
PDI G-101, PDI G-102Solid Waste IAPMO IGC 167
Non-petroleum OilASME A112.14.6, IAPMO PS 80,
PDI G-102
Petroleum OilASTM D6104, IAPMO IGC 183,
IAPMO IGC 3251009.2 Approval. The size, type, and location of each interceptor (clarifier) or separator shall be approved by the Authority Having Jurisdiction. Except where otherwise specifically permitted, no wastes other than those requiring treatment or separation shall be discharged into an interceptor (clarifier). 1009.3 Design. Interceptors (clarifiers) for sand and similar heavy solids shall be so designed and located as to be readily accessible for cleaning and shall have a water seal of not less than 6 inches (152 mm). 1009.4 Relief Vent. Interceptors (clarifiers) shall be so designed that they will not become air-bound where closed covers are used. Each interceptor (clarifier) shall be properly vented.
1009.5 Location. Each interceptor (clarifier) cover shall be readily accessible for servicing and maintaining the interceptor (clarifier) in working and operating condition. The use of ladders or the removal of bulky equipment to service interceptors (clarifiers) shall constitute a violation of accessibility. Location of interceptors (clarifiers) shall be shown on the approved building plan. 1009.6 Maintenance of Interceptors. Interceptors shall be maintained in efficient operating condition by periodic removal of accumulated grease, scum, oil, or other floating substances and solids deposited in the interceptor. 1009.7 Discharge. The waste pipe from oil and sand interceptors shall discharge as approved by the Authority Having Jurisdiction.
1010.0 Slaughterhouses, Packing Establishments, etc.
1010.1 General. A fish, fowl, and animal slaughterhouse or establishment; a fish, fowl, and meat packing or curing establishment; a soap factory, tallow-rendering, fat-rendering, and a hide-curing establishment shall be connected to and shall drain or discharge into an approved grease interceptor (clarifier).
TABLE 1009.1 APPROVED INTERCEPTORS (CLARIFIERS)
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TRAPS AND INTERCEPTORS
1010.2 Meat and Poultry Processing Plants. [AGR]
1010.2.1 Drainage and Plumbing Systems. Drainage and plumbing systems shall meet the require- ments of Section 724.0.
1010.2.1.1 Each floor drain shall be equipped with a deep-seal trap.
CPC § 1007.2 High relevance — show source text
1007.2 Trap Seal Primers. Potable water supply trap seal primer valves shall comply with ASSE 1018. Drainage or electronic design type trap seal primer devices shall comply with ASSE 1044 or IAPMO PS 76.
1008.0 Building Traps. 1008.1 General. Building traps shall not be installed except where required by the Authority Having Jurisdiction. Each building trap where installed shall be provided with a cleanout and with a relieving vent or fresh-air intake on the inlet side of the trap, which needs not be larger than one-half the diameter of the drain to which it connects. Such relieving vent or fresh-air intake shall be carried above grade and terminate in a screened outlet located outside the building.
1009.0 Interceptors (Clarifiers) and Separators.
1009.1 Where Required. Interceptors (clarifiers) (including grease, oil, sand, solid interceptors, etc.) shall be required
by the Authority Having Jurisdiction where they are necessary for the proper handling of liquid wastes containing grease, flammable wastes, sand, solids, acid or alkaline substances, or other ingredients harmful to the building drainage system, the public or private sewer, or to public or private sewage disposal. A list of acceptable interceptor standards is referenced in Table 1009.1.
TABLE 1009.1 APPROVED INTERCEPTORS (CLARIFIERS)
APPLICATION STANDARD
Fats, Oil, Grease
(FOG)ASME A112.14.3, ASME A112.14.4,
ASME A112.14.6, CSA B481,
ANSI/CAN/IAPMO Z1001,
PDI G-101, PDI G-102Solid Waste IAPMO IGC 167
Non-petroleum OilASME A112.14.6, IAPMO PS 80,
PDI G-102
Petroleum OilASTM D6104, IAPMO IGC 183,
IAPMO IGC 3251009.2 Approval. The size, type, and location of each interceptor (clarifier) or separator shall be approved by the Authority Having Jurisdiction. Except where otherwise specifically permitted, no wastes other than those requiring treatment or separation shall be discharged into an interceptor (clarifier). 1009.3 Design. Interceptors (clarifiers) for sand and similar heavy solids shall be so designed and located as to be readily accessible for cleaning and shall have a water seal of not less than 6 inches (152 mm). 1009.4 Relief Vent. Interceptors (clarifiers) shall be so designed that they will not become air-bound where closed covers are used. Each interceptor (clarifier) shall be properly vented.
CPC § 1004.2 High relevance — show source text
1004.2 Movable Parts. Bladders, check valves or another type of devices with moveable parts shall be prohibited to serve as a trap.
1005.0 Trap Seals. 1005.1 General. Each fixture trap shall have a liquid seal of not less than 2 inches (51 mm) and not more than 4 inches (102 mm), except where a deeper seal is found necessary by the Authority Having Jurisdiction. Traps shall be set true with respect to their liquid seals and, where necessary, they shall be protected from freezing.
1006.0 Floor Drain Traps. 1006.1 General. Floor drains shall connect into a trap so constructed that it can be readily cleaned and of a size to serve efficiently the purpose for which it is intended. The drain inlet shall be so located that it is in full view. Where subject to the reverse flow of sewage or liquid waste, such drains shall be equipped with an approved backwater valve.
1007.0 Trap Seal Protection. 1007.1 General. Floor drain or similar traps directly connected to the drainage system and subject to infrequent use shall be protected with a trap seal primer, except where not deemed necessary for safety or sanitation by the Authority Having Jurisdiction. Trap seal primers shall be accessible for maintenance.
1007.2 Trap Seal Primers. Potable water supply trap seal primer valves shall comply with ASSE 1018. Drainage or electronic design type trap seal primer devices shall comply with ASSE 1044 or IAPMO PS 76.
1008.0 Building Traps. 1008.1 General. Building traps shall not be installed except where required by the Authority Having Jurisdiction. Each building trap where installed shall be provided with a cleanout and with a relieving vent or fresh-air intake on the inlet side of the trap, which needs not be larger than one-half the diameter of the drain to which it connects. Such relieving vent or fresh-air intake shall be carried above grade and terminate in a screened outlet located outside the building.
1009.0 Interceptors (Clarifiers) and Separators.
1009.1 Where Required. Interceptors (clarifiers) (including grease, oil, sand, solid interceptors, etc.) shall be required
by the Authority Having Jurisdiction where they are necessary for the proper handling of liquid wastes containing grease, flammable wastes, sand, solids, acid or alkaline substances, or other ingredients harmful to the building drainage system, the public or private sewer, or to public or private sewage disposal. A list of acceptable interceptor standards is referenced in Table 1009.1.
TABLE 1009.1 APPROVED INTERCEPTORS (CLARIFIERS)
CPC § 1011.0 Medium relevance — show source text
1010.4 Horse Meat and Pet Food
Establishments . . . . . . . . . . . . . . .197
1010.5 Draining and Plumbing . . . . . . . .197
1011.0 Minimum Requirements for Auto Wash Racks . . . . . . . . . . . . .197
1011.1 General . . . . . . . . . . . . . . . . . . . . .197
1012.0 Commercial and Industrial
Laundries . . . . . . . . . . . . . . . . . . .197
1012.1 General . . . . . . . . . . . . . . . . . . . . .197
1013.0 Bottling Establishments . . . . . . . .197
1013.1 General . . . . . . . . . . . . . . . . . . . . .197
1014.0 Grease Interceptors . . . . . . . . . . .197
1014.1 General . . . . . . . . . . . . . . . . . . . . .197
1014.2 Hydromechanical Grease Interceptors . . . . . . . . . . . . . . . . . .198
Table 1014.2.1 Hydromechanical Grease Interceptor Sizing Using Gravity Flow Rates . . . . . . . . . . . .198
1014.3 Gravity Grease Interceptors . . . . .198
Table 1014.3.6 Gravity Grease Interceptor Sizing . . . . . . . . . . . . . . . . . . . . . .199
1015.0 FOG (Fats, Oils, and Greases) Disposal System . . . . . . . . . . . . . .199
1015.1 Purpose . . . . . . . . . . . . . . . . . . . .199
1015.2 Components, Materials, and Equipment . . . . . . . . . . . . . . . . . .200
1015.3 Sizing and Installation . . . . . . . . .200
1015.4 Performance . . . . . . . . . . . . . . . . .200
1016.0 Sand Interceptors . . . . . . . . . . . . .200
1016.1 Discharge . . . . . . . . . . . . . . . . . . .200
1016.2 Authority Having Jurisdiction . . . .200
1016.3 Construction and Size . . . . . . . . .200
1016.4 Separate Use . . . . . . . . . . . . . . . .200
1017.0 Oil and Flammable Liquid Interceptors . . . . . . . . . . . . . . . . . .200
1017.1 Interceptors Required . . . . . . . . . .200
1017.2 Interceptor Design Alternatives . . .200
1017.3 Interceptor Details . . . . . . . . . . . .200
1017.4 Design of Interceptors . . . . . . . . .200
CHAPTER 11 STORM DRAINAGE . . . . . . . . . .203
1101.0 General . . . . . . . . . . . . . . . . . . . . .205
CPC § 1009.1 Medium relevance — show source text
1009.1 Where Required . . . . . . . . . . . . . .196
Table 1009.1 Approved Interceptors (Clarifiers) . .196
1009.2 Approval . . . . . . . . . . . . . . . . . . . .196
1009.3 Design . . . . . . . . . . . . . . . . . . . . .196
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TABLE OF CONTENTS
1009.4 Relief Vent . . . . . . . . . . . . . . . . . .196
1009.5 Location . . . . . . . . . . . . . . . . . . . .196
1009.6 Maintenance of Interceptors . . . . .196
1009.7 Discharge . . . . . . . . . . . . . . . . . . .196
1010.0 Slaughterhouses, Packing Establishments, etc . . . . . . . . . . .196
1010.1 General . . . . . . . . . . . . . . . . . . . . .196
1010.2 Meat and Poultry Processing Plants . . . . . . . . . . . . . . . . . . . . . .197
1010.3 Collection Centers and
Facilities . . . . . . . . . . . . . . . . . . . .197
1010.4 Horse Meat and Pet Food
Establishments . . . . . . . . . . . . . . .197
1010.5 Draining and Plumbing . . . . . . . .197
1011.0 Minimum Requirements for Auto Wash Racks . . . . . . . . . . . . .197
1011.1 General . . . . . . . . . . . . . . . . . . . . .197
1012.0 Commercial and Industrial
Laundries . . . . . . . . . . . . . . . . . . .197
1012.1 General . . . . . . . . . . . . . . . . . . . . .197
1013.0 Bottling Establishments . . . . . . . .197
1013.1 General . . . . . . . . . . . . . . . . . . . . .197
1014.0 Grease Interceptors . . . . . . . . . . .197
1014.1 General . . . . . . . . . . . . . . . . . . . . .197
1014.2 Hydromechanical Grease Interceptors . . . . . . . . . . . . . . . . . .198
Table 1014.2.1 Hydromechanical Grease Interceptor Sizing Using Gravity Flow Rates . . . . . . . . . . . .198
1014.3 Gravity Grease Interceptors . . . . .198
Table 1014.3.6 Gravity Grease Interceptor Sizing . . . . . . . . . . . . . . . . . . . . . .199
CPC § 1014.2.1 Medium relevance — show source text
designed and installed so that the total flow through such device or devices shall at no time be greater than the rated flow of the connected grease interceptor. No flow control device having adjustable or removable parts shall be approved. The vented flow control device shall be located such that no system vent shall be between the flow control and the grease interceptor inlet. The vent or air inlet of the flow control device shall connect with the sanitary drainage vent system, as elsewhere required by this code, or shall terminate through the roof of the building, and shall not terminate to the free atmosphere inside the building.
Exception: Listed grease interceptors with integral flow controls or restricting devices shall be installed in an accessible location in accordance with the manufacturer’s installation
instructions.
1014.2.1 Capacity. The total capacity in gallons (gal) (L) of fixtures discharging into a hydromechanical grease interceptor shall not exceed two and one-half times the certified gallon per minute (gpm) (L/s) flow rate of the interceptor in accordance with Table 1014.2.1.
For this section, the term “fixture” shall mean and include each plumbing fixture, appliance, apparatus, or other equipment required to be connected to or discharged into a grease interceptor by a provision of this section.
1014.2.2 Vent. A vent shall be installed downstream of
hydromechanical grease interceptors in accordance with the requirements of this code.
TABLE 1014.2.1
HYDROMECHANICAL GREASE INTERCEPTOR SIZING USING GRAVITY FLOW RATES [1]
DIAMETER OF
GREASE WASTE
PIPE (inches)MAXIMUM FULL
PIPE FLOW
(gpm)2SIZE OF GREASE INTERCEPTOR Col4
DIAMETER OF
GREASE WASTE
PIPE (inches)MAXIMUM FULL
PIPE FLOW
(gpm)2ONE-MINUTE
DRAINAGE
PERIOD
(gpm)TWO-MINUTE
DRAINAGE
PERIOD
(gpm)
220 20 10
360 75 35
4125 150 75
5230 250 125
6375 400 200 For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s
Notes: 1 For interceptor sizing by the fixture capacity see the example below. 2 1 ∕ 4 inch slope per foot (20.8 mm/m) based on Manning’s formula with friction factor N = 0.012.
EXAMPLE 1014.2.1
SIZING HYDROMECHANICAL GREASE INTERCEPTOR(S)
USING FIXTURE CAPACITY
Step 1: Determine the flow rate from each fixture.
[Length] X [Width] X [Depth] / [231] = Gallons X [0.75 fill factor] / [Drain
Period (1 minute or 2 minutes)]
Step 2: Calculate the total load from fixtures that discharge into
the interceptor.
CPC § 0.06 Medium relevance — show source text
For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s
Notes: 1 For interceptor sizing by the fixture capacity see the example below. 2 1 ∕ 4 inch slope per foot (20.8 mm/m) based on Manning’s formula with friction factor N = 0.012.
EXAMPLE 1014.2.1
SIZING HYDROMECHANICAL GREASE INTERCEPTOR(S)
USING FIXTURE CAPACITY
Step 1: Determine the flow rate from each fixture.
[Length] X [Width] X [Depth] / [231] = Gallons X [0.75 fill factor] / [Drain
Period (1 minute or 2 minutes)]
Step 2: Calculate the total load from fixtures that discharge into
the interceptor.
FIXTURES COMPART-
MENTSLOAD
(gallons)SIZE OF
GREASE
INTERCEPTOR
ONE-MINUTE
DRAINAGE
PERIOD
(gpm)TWO-
MINUTE
DRAINAGE
PERIOD
(gpm)
Compartment
size–– –– –– ––
24 inches x 24
inches x 12
inches2 44.9 –– ––
Hydrant–– 3 –– ––
Rated
Appliance–– 2 –– ––
–––– 49.9 50 25 For SI units: 1 inch = 25.4 mm, 1 gallon per minute = 0.06 L/s, 1 gallon =
3.785 L
1014.3 Gravity Grease Interceptors. Required gravity grease interceptors shall comply with the provisions of Section 1014.3.1 through Section 1014.3.7.
1014.3.1 General. The provisions of this section shall apply to the design, construction, installation, and testing of commercial kitchen gravity grease interceptors.
1014.3.2 Waste Discharge Requirements. Waste discharge in establishments from fixtures and equipment
For SI units: 1 inch = 25.4 mm, 1 gallon per minute = 0.06 L/s, 1 gallon =
3.785 L
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TRAPS AND INTERCEPTORS
which contain grease, including but not limited to, scullery sinks, pot and pan sinks, dishwashers, soup kettles, and floor drains located in areas where grease-containing materials exist, shall be permitted to be drained into the sanitary waste through the interceptor where approved by the Authority Having Jurisdiction.
1014.3.2.1 Toilets and Urinals. Toilets, urinals, and other similar fixtures shall not drain through the interceptor.
1014.3.2.2 Inlet Pipe. Waste shall enter the interceptor through the inlet pipe.
1014.3.3 Design. Gravity interceptors shall be constructed in accordance with the applicable standard in Chapter 17 or the design approved by the Authority Having Jurisdiction.
CPC § 901.0 Medium relevance — show source text
H 901.0 Commercial or Industrial Special Liquid- Waste Disposal.
H 901.1 Interceptor. Where liquid wastes contain excessive amounts of grease, garbage, flammable wastes, sand, or other ingredients that affect the operation of a private sewage disposal system, an interceptor for such wastes shall be installed.
H 901.2 Installation. Installation of such interceptors shall comply with Section 1009.0 of this code, and their location shall comply with Table H 101.8 of this appendix. H 901.3 Sampling Box. A sampling box shall be installed where required by the Authority Having Jurisdiction. H 901.4 Design and Structural Requirement. Interceptors shall be of approved design and be not less than two compartments. Structural requirements shall comply with Section H 501.0 of this appendix.
H 901.5 Location. Interceptors shall be located as close to the source as possible and be accessible for servicing. Necessary manholes for servicing shall be at grade level and be gastight.
H 901.6 Waste Discharge. Waste discharge from interceptors shall be permitted to be connected to a septic tank or other primary system or be disposed into a separate disposal system. H 901.7 Design Criteria. A formula shall be permitted to be adapted to other types of occupancies with similar wastes. (See Chart H 901.7)
H 1001.0 Inspection and Testing. H 1001.1 Inspection. Inspection requirements shall comply with the following:
(1) Applicable provisions of Section 105.0 of this code and this appendix shall be required. Plans shall be required in accordance with Section 103.3 of this code.
(2) System components shall be properly identified as to manufacturer. Septic tanks or other primary systems shall have the rated capacity permanently marked on the unit.
(3) Septic tanks or other primary systems shall be installed on dry, level, well-compacted soil.
(4) Where design is predicated on soil tests, the system shall be installed at the same location and depth as the tested
area.
H 1001.2 Testing. Testing requirements shall comply with the following:
(1) Septic tanks or other primary components shall be filled with water to flow line before requesting an inspection. Seams or joints shall be left exposed (except the bottom), and the tank shall remain watertight.
(2) A flow test shall be performed through the system to the point of effluent disposal. All lines and components shall
CHART H 901.7
RECOMMENDED DESIGN CRITERIA
GREASE AND GARBAGE, COMMERCIAL KITCHENS Number of meals per peak hour x Waste flow rate [1] x Retention time [2] x Storage factor [3] = (Interceptor size liquid capacity)
SAND-SILT OIL, AUTO WASHERS vehicles Number of per hour x Waste flow rate [1] x Retention time [2] x Storage factor [3] = (Interceptor size liquid capacity)
SILT-LINT GREASE, LAUNDRIES, LAUNDROMATS
Number of x 2 cycles per x Waste flow x Retention time [2] = Storage factor [3] = Interceptor size machines hour rate [1] (liquid capacity)
Notes: 1 For waste flow rate see Table H 201.1(4). 2 Retention Times:
CPC § 1014.3.4 Medium relevance — show source text
1014.3.4 Location. Each grease interceptor shall be so installed and connected that it shall be easily accessible for inspection, cleaning, and removal of the intercepted grease. A gravity grease interceptor that complies with ANSI/CAN/IAPMO Z1001 shall not be installed in a
building where food is handled. Location of the grease interceptor shall meet the approval of the Authority Having Jurisdiction.
1014.3.4.1 Interceptors. Interceptors shall be placed as close as practical to the fixtures they serve.
1014.3.4.2 Business Establishment. Each
business establishment for which a gravity grease interceptor is required shall have an interceptor which shall serve that establishment unless other wise approved by the Authority Having Jurisdiction.
1014.3.4.3 Access. Each gravity grease interceptor shall be located to be readily accessible to the equipment required for maintenance.
1014.3.5 Construction Requirements. Gravity grease interceptors shall be designed to remove grease from effluent and shall be sized in accordance with this
section. Gravity grease interceptors shall also be designed to retain grease until accumulations can be removed by pumping the interceptor. When provided, a sample box shall be located at the outlet end of gravity grease interceptors so that the Authority Having Jurisdiction can periodically sample effluent quality.
1014.3.6 Sizing Criteria. The volume of the interceptor shall be determined by using Table 1014.3.6. Where drainage fixture units (DFUs) are not known, the interceptor shall be sized based on the maximum DFUs allowed for the pipe size connected to the inlet of the interceptor. Refer to Table 703.2, Drainage Piping, Horizontal.
1014.3.7 Abandoned Gravity Grease Intercep- tors. Abandoned grease interceptors shall be pumped and filled as required for abandoned sewers and sewage disposal facilities in Section 722.0.
DRAINAGE FIXTURE UNITS1, 3
(DFUs)INTERCEPTOR VOLUME2
(gallons)
8500
21750
351000
901250 172 1500
2162000
3072500
3423000
4284000
5765000
7207500 2112 10 000
264015 000 For SI units: 1 gallon = 3.785 L
Notes: 1 The maximum allowable DFUs plumbed to the kitchen drain lines that will be connected to the grease interceptor. 2 This size is based on DFUs, the pipe size from this code; Table 703.2; Useful Tables for flow in half-full pipes (ref: Mohinder Nayyar Piping Handbook, 3rd Edition, 1992). Based on 30-minute retention time (ref.: George Tchobanoglous and Metcalf & Eddy. Wastewater Engineering Treatment, Disposal, and Reuse, 3rd Ed. 1991 & Ronald Crites and George Tchobanoglous. Small and Decentralized Wastewater Management Systems, 1998). Rounded up to nominal interceptor volume.
CPC § 1014.3.7 Medium relevance — show source text
1014.3.7 Abandoned Gravity Grease Intercep- tors. Abandoned grease interceptors shall be pumped and filled as required for abandoned sewers and sewage disposal facilities in Section 722.0.
DRAINAGE FIXTURE UNITS1, 3
(DFUs)INTERCEPTOR VOLUME2
(gallons)
8500
21750
351000
901250 172 1500
2162000
3072500
3423000
4284000
5765000
7207500 2112 10 000
264015 000 For SI units: 1 gallon = 3.785 L
Notes: 1 The maximum allowable DFUs plumbed to the kitchen drain lines that will be connected to the grease interceptor. 2 This size is based on DFUs, the pipe size from this code; Table 703.2; Useful Tables for flow in half-full pipes (ref: Mohinder Nayyar Piping Handbook, 3rd Edition, 1992). Based on 30-minute retention time (ref.: George Tchobanoglous and Metcalf & Eddy. Wastewater Engineering Treatment, Disposal, and Reuse, 3rd Ed. 1991 & Ronald Crites and George Tchobanoglous. Small and Decentralized Wastewater Management Systems, 1998). Rounded up to nominal interceptor volume. 3 Where the flow rate of directly connected fixture(s) or appliance(s) have no assigned DFU values, the additional grease interceptor volume shall be based on the known flow rate (gpm) (L/s) multiplied by 30 minutes.
EXAMPLE 1014.3.6
GRAVITY GREASE INTERCEPTOR SIZING EXAMPLE
Given: A restaurant with the following fixtures and equip ment.
One food preparation sink; three-floor drains - one in the food prep area, one in the grill area, and one receiving the indirect waste from the ice machine and a mop sink.
Kitchen Drain Line DFU Count (from Table 702.1):
3 floor drains at 2 DFUs each = 6 DFUs
Mop sink at 3 DFUs each = 3 DFUs
Food prep sink at 3 DFUs each = 3 DFUs
Total = 12 DFUs
Using Table 1014.3.6, the grease interceptor will be sized at 750 gallons (2389 L).
1015.0 FOG (Fats, Oils, and Greases) Disposal Sys- tem.
1015.1 Purpose. The purpose of this section is to provide the necessary criteria for the sizing, application, and installation of FOG disposal systems designated as a pretreatment or discharge water quality compliance strategy.
TABLE 1014.3.6
GRAVITY GREASE INTERCEPTOR SIZING
2025 CALIFORNIA PLUMBING CODE 199
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
TRAPS AND INTERCEPTORS
CPC § 1015.4 Medium relevance — show source text
1015.4 Performance. FOG disposal systems shall produce an effluent quality not to exceed 5.84 grains per gallon (gr/gal) (100 mg/L) FOG. 1015.5 [OSHPD 1, 1R, 2, 3, 4 & 5] Grease interceptors shall not be installed in food preparation area of kitchens. 1015.6 [OSHPD 1, 1R, 2, 3, 4 & 5] Grease interceptors shall be installed outside of the kitchen area in location affording ease of maintenance and servicing.
1016.0 Sand Interceptors.
1016.1 Discharge. Where the discharge of a fixture or drain contains solids or semi-solids heavier than water that would be harmful to a drainage system or cause a stoppage within the system, the discharge shall be through a sand interceptor. Multiple floor drains shall be permitted to discharge into one sand interceptor. 1016.2 Authority Having Jurisdiction. Sand interceptors are required where the Authority Having Jurisdiction deems it advisable to have a sand interceptor to protect the drainage system. 1016.3 Construction and Size. Sand interceptors shall be built of brick or concrete, prefabricated coated steel, or other watertight material. The interceptor shall have an interior baffle for full separation of the interceptor into two sections. The outlet pipe shall be the same size as the inlet pipe of the sand interceptor, the minimum being 3 inches (80 mm), and the baffle shall have two openings of the same diameter as the outlet pipe and at the same invert as the outlet pipe. These openings shall be staggered so that there cannot be a straight line flow between the inlet pipe and the outlet pipe. The invert of the inlet pipe shall be no lower than the invert of the outlet pipe.
The sand interceptor shall have a minimum dimension of 2 square feet (0.2 m [2] ) for the net free opening of the inlet section and a minimum depth under the invert of the outlet pipe of 2 feet (610 mm).
For each 5 gpm (0.3 L/s) flow or fraction thereof over 20 gpm (1.26 L/s), the area of the sand interceptor inlet section is to be increased by 1 square foot (0.09 m [2] ). The outlet section shall at all times have a minimum area of 50 percent of the inlet section.
The outlet section shall be covered by a solid removable cover, set flush with the finished floor, and the inlet section shall have an open grating, set flush with the finished floor and suitable for the traffic in the area in which it is located.
1016.4 Separate Use. Sand and similar interceptors for every solid shall be so designed and located as to be readily accessible for cleaning, shall have a water seal of not less than 6 inches (152 mm), and shall be vented.
1017.0 Oil and Flammable Liquid Interceptors.
1017.1 Interceptors Required. Repair garages and gasoline stations with grease racks or grease pits, and factories that have oily, flammable, or both types of wastes as a result of manufacturing, storage, maintenance, repair, or testing processes, shall be provided with an oil or flammable liquid interceptor. Floor drains in such locations shall be connected directly to oil and flammable liquid interceptors.
Frequently asked questions
When is an interceptor required?
The CPC says an interceptor is required where necessary to protect the drainage system or sewer from grease, oil, sand, solids or other harmful wastes — see § 1009.1 .
Which standard must a grease interceptor meet?
FOG interceptors are expected to comply with the standards listed in Table 1009.1 (ASME A112.14.x series, CSA B481, PDI G‑101/G‑102, etc.) — Table 1009.1 .
How do I size a hydromechanical interceptor?
Size by calculating fixture discharge (one‑ or two‑minute drain period) and selecting an interceptor whose certified gpm meets the rule: Fixture gallons ≤ 2.5 × certified gpm. Reference § 1014.2.1 and Table 1014.2.1 .
How do I size a gravity interceptor?
Use the kitchen drain DFU total and map to volume using Table 1014.3.6 (30‑minute retention basis); where DFUs are unknown, use known gpm × 30 minutes as allowed in the table notes — § 1014.3.6 .
Can I put a grease interceptor inside the kitchen?
Certain listed interceptors or configurations are not allowed inside food prep areas; check § 1014.3.4 and local AHJ/OSHPD rules (see § 1015.5) before locating inside the kitchen — § 1014.3.4, § 1015.5 .
More in California Plumbing Code
- Administration
- Definitions
- General Regulations
- Plumbing Fixtures and Fixture Fittings
- Water Heaters
- Water Supply and Distribution
- Sanitary Drainage (Drain, Waste, and Vent)
- Indirect Wastes
- Vents
- Traps and Interceptors
- Storm Drainage
- Fuel Gas Piping
- Health Care Facilities — Medical Gas and Medical Vacuum Systems
- Alternate Water Sources and Nonpotable Rainwater Catchment Systems
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