CPC · California Plumbing Code
Sand interceptor construction, sizing, access and venting
If heavy solids will discharge to your drain, the CPC requires a two‑compartment, watertight sand interceptor sized by inlet area (minimum 2 sq ft, +1 sq ft per 5 gpm over 20 gpm), with staggered baffle openings, inlet and outlet piping the same size (minimum 3"), a minimum 2‑ft depth under the outlet invert, a 6‑inch trap seal, solid outlet cover and grated inlet, ready access for cleaning, and venting as required by the AHJ.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
The California Plumbing Code requires that discharges containing solids heavier than water be routed through a sand interceptor and that such interceptors be constructed, sized, accessed and vented according to the CPC. Key controlling sections are § 1016.1, § 1016.3, and § 1016.4.
A sand interceptor must be a two-compartment, watertight device with an interior baffle, a minimum inlet area and depth, a minimum outlet pipe size, a minimum trap (water) seal, and must be accessible for cleaning and vented.
Requirements in detail
When is a sand interceptor required?
- Where a fixture or drain discharges solids or semi‑solids heavier than water that could harm or stop the drainage system, the discharge must go through a sand interceptor (§ 1016.1). Multiple floor drains may be tied to a single interceptor.
Construction materials and basic configuration
Interceptors must be built of brick or concrete, prefabricated coated steel, or other watertight material and must contain an interior baffle that fully separates the unit into two sections. The inlet and outlet piping and baffle openings must be arranged to prevent straight‑line flow. § 1016.3 controls these details.
The outlet pipe shall be the same size as the inlet pipe, with a minimum size of 3 inches (80 mm). The baffle shall have two openings equal to the outlet pipe diameter and at the same invert as the outlet pipe; the openings must be staggered so there is no straight-line flow between inlet and outlet. The invert of the inlet shall not be lower than the invert of the outlet. § 1016.3.
Minimum dimensions, area and depth (sizing rule)
Base minimums:
- Inlet section net free opening: 2 square feet (0.2 m²) minimum. § 1016.3.
- Depth under the invert of the outlet pipe: 2 feet (610 mm) minimum. § 1016.3.
Flow‑based enlargement:
- For each 5 gpm (0.3 L/s) or fraction thereof over 20 gpm (1.26 L/s), add 1 square foot (0.09 m²) to the inlet section area. The outlet section must always have at least 50% of the inlet section area. § 1016.3.
Covers, gratings and floor integration
- The outlet section must be covered by a solid removable cover, set flush with the finished floor. The inlet section must have an open grating, set flush with the finished floor and suitable for the traffic in the area. § 1016.3.
Access, water seal and venting
- Sand interceptors must be readily accessible for cleaning, have a water seal not less than 6 inches (152 mm), and shall be vented (§ 1016.4). The broader interceptor/clarifier provisions also require design to avoid becoming air‑bound and require proper venting. § 1016.4; see also § 1009.3 and § 1009.4 for accessibility, minimum water seal and venting guidance.
Decision‑relevant dimensions/values (quick reference)
| Item | Required value / rule | Code Reference |
|---|---|---|
| Minimum inlet net free opening | 2 sq ft (0.2 m²) | § 1016.3 |
| Minimum depth under outlet invert | 2 ft (610 mm) | § 1016.3 |
| Outlet pipe minimum diameter | 3 in (80 mm); outlet = inlet size | § 1016.3 |
| Baffle openings | Two openings same diameter as outlet; staggered; at outlet invert | § 1016.3 |
| Inlet invert elevation | Not lower than the outlet invert | § 1016.3 |
| Increase inlet area for high flow | +1 sq ft per 5 gpm (0.3 L/s) or fraction over 20 gpm (1.26 L/s) | § 1016.3 |
| Minimum outlet section area | ≥ 50% of inlet section area | § 1016.3 |
| Covering | Outlet = solid removable cover flush with floor; Inlet = open grating suitable for traffic | § 1016.3 |
| Accessibility & water seal | Readily accessible for cleaning; water seal ≥ 6 in (152 mm); vented | § 1016.4 and § 1009.3/1009.4 |
Exceptions & special cases
The Authority Having Jurisdiction (AHJ) may require sand interceptors where deemed advisable; AHJ approval is required for size/type/location in general. § 1016.2 and related interceptor approval provisions apply. If the AHJ determines an alternate design is appropriate, that authority governs.
The CPC allows multiple floor drains to discharge into one sand interceptor (no numeric limit specified), but the AHJ must approve the overall arrangement. § 1016.1.
The CPC specifies venting is required, but these sections do not provide a numeric vent‑diameter or termination detail for sand interceptors; where additional vent sizing or termination rules are needed (or to prevent air‑binding with closed covers), consult general venting provisions and the AHJ. See § 1016.4 and § 1009.4.
Common mistakes
- Designing inlet and outlet in a straight line (not staggering baffle openings), which defeats separation — baffle openings must be staggered at the outlet invert (§ 1016.3).
- Making the inlet invert lower than the outlet invert (violates § 1016.3).
- Undersizing inlet area (forgetting to add 1 sq ft per 5 gpm or fraction above 20 gpm) — a frequent miscalculation. § 1016.3.
- Installing a perforated or open cover on the outlet section (outlet requires a solid removable cover; inlet is the grating). § 1016.3.
- Omitting a 6‑inch (152 mm) water seal or failing to provide access for cleaning — both required. § 1016.4 and § 1009.3.
Worked example — concrete scenario
Scenario: A maintenance bay has three floor drains that together discharge a peak flow of 28 gpm (1.68 L/s) to a single sand interceptor.
- Base inlet area = 2 sq ft (covers up to 20 gpm) per § 1016.3.
- Flow over 20 gpm = 28 − 20 = 8 gpm. For each 5 gpm or fraction thereof over 20, add 1 sq ft. 8 gpm = two increments (5 gpm + remainder), so add 2 sq ft. Total inlet area = 4 sq ft. § 1016.3.
- Outlet section area must be at least 50% of inlet area → ≥ 2 sq ft. § 1016.3.
- Depth under outlet invert must be ≥ 2 ft (610 mm); ensure design meets that vertical dimension. § 1016.3.
- Provide inlet & outlet piping of the same diameter, minimum 3 in (80 mm). Make the baffle openings the same diameter, at the outlet invert and staggered to avoid straight‑line flow. § 1016.3.
- Provide a solid removable cover for the outlet (flush with floor) and an open grating for the inlet suitable for traffic. § 1016.3.
- Ensure the interceptor is readily accessible for cleaning, has a water seal ≥ 6 in (152 mm) and is vented. § 1016.4 and § 1009.3/1009.4.
Related provisions
- § 1016.1 — Discharge requirement for sand interceptors (when required).
- § 1016.2 — Authority Having Jurisdiction may require interceptors and approve size/type/location.
- § 1016.3 — Construction, piping, baffle, sizing, covers and traffic loading requirements.
- § 1016.4 — Accessibility, 6 in (152 mm) water seal and venting requirement.
- § 1009.3 — Interceptors for sand and heavy solids: accessibility and 6 in seal reference.
- § 1009.4 — Relief vent / venting to prevent air‑binding and requirement that each interceptor be properly vented.
Note: The CPC text retrieved requires venting but does not specify a numeric vent diameter or precise termination method for sand interceptors in § 1016.4; for vent sizing/termination details consult the general venting chapter and the AHJ.
Code references
Grounded in the retrieved California Plumbing Code — click a citation to read the verbatim passage:
CPC § 1015.4 High 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.
CPC § 0.2 High relevance — show source text
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.
1017.2 Interceptor Design Alternatives. Oil interceptors shall comply with IAPMO IGC 183 or be in accordance with Section 1017.3 through Section 1017.4.
1017.3 Interceptor Details. Oil and flammable liquid interceptors shall be in accordance with the following:
(1) The separation or vapor compartment shall be independently vented to the outer air. Where two or more separation or vapor compartments are used, each shall be vented to the outer air or shall be permitted to connect to a header that is installed at a minimum of 6 inches (152 mm) above the spill line of the lowest floor drain and vented independently to the outer air.
(2) The minimum size of a flammable vapor vent shall be not less than 2 inches (50 mm), and, where vented through a sidewall, the vent shall be not less than 10 feet (3048 mm) above the adjacent level at an approved location.
(3) The interceptor shall be vented on the sewer side and shall not connect to a flammable vapor vent. Oil and flammable interceptors shall be provided with gastight cleanout covers that shall be readily accessible.
(4) The waste line shall be not less than 3 inches (80 mm) in diameter with a full-size cleanout to grade.
(5) Where an interceptor is provided with an overflow, it shall be provided with an overflow line [not less than 2 inches (50 mm) in diameter] to an approved waste oil tank having a minimum capacity of 550 gallons (2082 L) and meeting the requirements of the Authority Having Jurisdiction.
(a) The waste oil from the separator shall flow by gravity or shall be pumped to a higher elevation by an automatic pump.
CPC § 1015.0 High relevance — show source text
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
1101.1 Applicability . . . . . . . . . . . . . . . . . .205
1101.2 Where Required . . . . . . . . . . . . . .205
1101.3 Storm Water Drainage to Sanitary Sewer Prohibited . . . . . .205
1101.4 Material Uses . . . . . . . . . . . . . . . .205
Table 1101.4.6 Materials for Subsoil Drainpipe and Fittings . . . . . . . . . . . . . . . . . .205
1101.5 Expansion Joints Required . . . . . .205
1101.6 Subsoil Drains . . . . . . . . . . . . . . .205
1101.7 Building Subdrains . . . . . . . . . . . .206
1101.8 Areaway Drains . . . . . . . . . . . . . .206
1101.9 Window Areaway Drains . . . . . . .206
1101.10 Filling Stations and Motor Vehicle Washing Establishments . . . . . . . . . . . . . . .206
1101.11 Paved Areas . . . . . . . . . . . . . . . . .206
1101.12 Roof Drainage . . . . . . . . . . . . . . .206
1101.13 Cleanouts . . . . . . . . . . . . . . . . . . .207
1101.14 Rainwater Sumps . . . . . . . . . . . . .207
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 § 1609.3.1. High relevance — show source text
Provisions shall be made for drainage by a riser of not less than1/8 inch at each nail or by 4-foot-
long battens with not less than a1/2-inch separation between battens. Horizontal battens are required for slopes over 7:12.
e. Perimeter fastening areas include three tile courses but not less than 36 inches from either side of hips or ridges and edges of eaves and_gable_ rakes.
f._ Vasd_ shall be determined in accordance with Section 1609.3.1.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s, 1 pound per square foot = 4.882 kg/m2.
a. Minimum fastener size. Corrosion-resistant nails not less than No. 11 gage with5/16-inch head. Fasteners shall be long enough to penetrate into the sheathing3/4 inch or
through the thickness of the sheathing, whichever is less. Attaching wire for clay and concrete tile shall not be smaller than 0.083 inch.
b. Snow areas. Not fewer than two fasteners per tile are required or battens and one fastener.
c. Roof slopes greater than 24:12. The nose of all tiles shall be securely fastened.
d. Horizontal battens. Battens shall be not less than 1 inch by 2 inches nominal. Provisions shall be made for drainage by a riser of not less than1/8 inch at each nail or by 4-foot-
long battens with not less than a1/2-inch separation between battens. Horizontal battens are required for slopes over 7:12.
e. Perimeter fastening areas include three tile courses but not less than 36 inches from either side of hips or ridges and edges of eaves and_gable_ rakes.
f._ Vasd_ shall be determined in accordance with Section 1609.3.1.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s, 1 pound per square foot = 4.882 kg/m2.
a. Minimum fastener size. Corrosion-resistant nails not less than No. 11 gage with5/16-inch head. Fasteners shall be long enough to penetrate into the sheathing3/4 inch or
through the thickness of the sheathing, whichever is less. Attaching wire for clay and concrete tile shall not be smaller than 0.083 inch.
b. Snow areas. Not fewer than two fasteners per tile are required or battens and one fastener.
c. Roof slopes greater than 24:12. The nose of all tiles shall be securely fastened.
d. Horizontal battens. Battens shall be not less than 1 inch by 2 inches nominal. Provisions shall be made for drainage by a riser of not less than1/8 inch at each nail or by 4-foot-
long battens with not less than a1/2-inch separation between battens. Horizontal battens are required for slopes over 7:12.
e.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 § 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 § 1017.4 Medium relevance — show source text
(b) Pumps shall be adequately sized and accessible.
(c) Waste oil tanks shall have a 2 inch (50 mm) minimum pump-out connection at grade and an 1 [1] ⁄ 2 inch (40 mm) minimum vent to atmosphere at an approved location not less than 10 feet (3048 mm) above grade. 1017.4 Design of Interceptors. Each manufactured interceptor that is rated shall be stamped or labeled by the manufacturer with an indication of its full discharge rate in gpm (L/s). The following shall apply:
(1) The full discharge rate to such an interceptor shall be determined at full flow. Each interceptor shall be rated equal to or greater than the incoming flow and shall be provided with an overflow line to an underground tank.
(2) Interceptors not rated by the manufacturer shall have a depth of not less than 2 feet (610 mm) below the invert of the discharge drain. The outlet opening shall have not
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TRAPS AND INTERCEPTORS
less than an 18 inch (457 mm) water seal and shall have a minimum capacity as follows:
(a) Where not more than three motor vehicles are serviced, stored, or both, interceptors shall have a minimum capacity of 6 cubic feet (0.2 m [3] ), and 1 cubic foot (0.03 m [3] ) of capacity shall be added for each vehicle up to 10 vehicles.
(b) Above 10 vehicles, the Authority Having Jurisdiction shall determine the size of the interceptor required.
(c) Where vehicles are serviced and not stored, interceptor capacity shall be based on a net capacity of 1 cubic foot (0.03 m [3] ) for each 100 square feet (9.29 m [2] ) of the surface to be drained into the interceptor, with a minimum of 6 cubic feet (0.2 m [3] ).
2025 CALIFORNIA PLUMBING CODE 201
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CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE
CHAPTER 11 - STORM DRAINAGE
(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
CPC § 10-5 Medium relevance — show source text
1002 Maintenance and Plans . . . . . . . . . . . . . . . . . . . . . . . . 10-5
1003 General Means of Egress . . . . . . . . . . . . . . . . . . . . . . . 10-5
1004 Occupant Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7
1005 Means of Egress Sizing. . . . . . . . . . . . . . . . . . . . . . . . . 10-9
1006 Number of Exits and Exit Access Doorways . . . . . 10-10
1007 Exit and Exit Access Doorway Configuration . . . . 10-14
1008 Means of Egress Illumination . . . . . . . . . . . . . . . . . . 10-14
1009 Accessible Means of Egress. . . . . . . . . . . . . . . . . . . . 10-15
1010 Doors, Gates and Turnstiles . . . . . . . . . . . . . . . . . . . 10-19
1011 Stairways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-29
1012 Ramps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-33
1013 Exit Signs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-34
1014 Handrails. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-36
1015 Guards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-37
1016 Exit Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-39
1017 Exit Access Travel Distance. . . . . . . . . . . . . . . . . . . . 10-40
1018 Aisles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-41
1019 Exit Access Stairways and Ramps . . . . . . . . . . . . . . 10-42
1020 Corridors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-42
1021 Egress Balconies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-44
1022 Exits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-44
CPC § 2025 Medium relevance — show source text
The waste must be treated to prevent any damage to the piping or sewage treatment process. Waste receptors are sized and designed to prevent splashing and allow for peak discharge conditions.
Chapter 9 Vents.
Chapter 9 regulates the material, design, and installation of vents. A vent system is a pipe or pipes installed in a drainage system that provide a flow of air to and from the system to ventilate it, provide a circulation of air to eliminate trap siphonage, and reduce back-pressure and vacuum surge. In addition, vents provide the rapid and silent flow of waste without exposing occupants of the building to any sewer gases. Proper installation of vents is crucial, as a telltale sign that there is a problem in the drain and vent system is related to the elevation of the horizontal portion of the venting. Venting is not limited to sanitary drainage systems. Venting methods are applicable to other drainage systems such as those for chemical waste, graywater waste, and clear water waste. Sizing the venting system is directly tied to the design of the drainage system. For example, the velocities in the drainage system and its peak flow rates affect the diameters in the venting system. Where the vertical distance between a fixture outlet and trap is excessive, velocities in the entire drainage system will be greater than those in the vent sizing table. All venting methods in this chapter are categorized as either dry vents or wet vents. Vent stacks, stack vents, branch vents, island vents, relief vents, and individual vents are dry vents. Wet vents (horizontal or vertical), circuit vents, combination drain and vents are versions of “wet venting” in which the vent is wetted by drainage flow.
2025 CALIFORNIA PLUMBING CODE xv
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
FORMAT OF THE UNIFORM PLUMBING CODE
Chapter 10 Traps and Interceptors.
Chapter 10 regulates the material, design, and installation of traps, interceptors, and separators. Traps are required on drainage type plumbing fixtures and must be self-scouring without interior partitions. Interceptors, on the other hand, are designed to control what goes down a drain. Interceptors are used to keep harmful substances from entering the sanitary drainage system, such as grease, sand, oil and other materials. The retained materials need periodic removal to maintain efficiency and function of the separating device. The capacity of an interceptor is based on retention and flow rate. There are many types of interceptors that are used at beauty salons, hospitals, meat, fish or foul packaging, refineries, repair garages, gas stations, car washing facilities, various plants, factories, and processing sites. The designer of the building is responsible for locating interceptors with the expectation for the frequency of maintenance, ease of cleaning and floor space for equipment.
Chapter 11 Storm Drainage.
Chapter 11 regulates the removal of stormwater from roofs, yards, paved areas, and similar areas. The objective of storm drainage systems is to provide a conduit or channel through which runoff will be carried from a point of collection to a point of disposal; this protects the property and the public from the uncontrolled flow of runoff and ensures that drains and inlets are adequately sized to receive the volume of runoff that flows to the drains. For the purpose of system design, it’s necessary to specify the duration of a selected storm.
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
198 2025 CALIFORNIA PLUMBING CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
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 § 1007.2 Medium 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.
Frequently asked questions
Do sand interceptors have to be two compartments?
Yes. The CPC requires an interior baffle that fully separates the interceptor into two sections. § 1016.3.
How do I calculate inlet area if flow is 45 gpm?
Base 2 sq ft covers up to 20 gpm. Flow over 20 = 25 gpm → that’s 5 increments of 5 gpm (or fractions) → add 5 sq ft. Total inlet area = 7 sq ft. § 1016.3.
Is there a required minimum outlet pipe size?
Yes — the outlet pipe must be the same size as the inlet and not less than 3 inches (80 mm). § 1016.3.
Do sand interceptors require a water trap?
Yes — a minimum water seal of 6 inches (152 mm) is required and the interceptor must be vented. § 1016.4 and § 1009.3.
Can I put the interceptor under heavy equipment?
Not if the cover or access would not be “readily accessible” for cleaning or if the inlet grating/cover is not suitable for traffic. The CPC requires covers and gratings be set flush and suitable for the traffic in the area and that interceptors be readily accessible. § 1016.3, § 1016.4.
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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