CPC · California Plumbing Code

Hydromechanical vs gravity grease interceptors: sizing, flow controls and venting

Q: What determines whether I can use a hydromechanical or gravity interceptor?

Choice is driven by space and hydraulic needs: HGIs are flow‑rated and compact (used where indoor space and flow‑control are practical) while GGIs are volumetric, require larger outdoor space and provide 30‑minute retention. Confirm applicability and sizing using § 1014.2 / § 1014.2.1 for HGIs and § 1014.3.6 / § 1014.3.1 for GGIs.

Q: How do I size an HGI when pipe diameter and DFUs are both available?

HGIs are sized by flow (use Table 1014.2.1 or fixture capacity method of § 1014.2.1 ); gravity interceptors use DFUs → volume (Table 1014.3.6). Use the method appropriate to the interceptor type being installed.

Hydromechanical interceptors are flow‑rated and must use an approved vented, nonadjustable flow control and be sized so fixtures served do not exceed 2.5× the interceptor’s certified gpm; gravity interceptors are sized by DFUs to a required volume (30‑minute retention).

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

Hydromechanical grease interceptors must discharge through an approved vented flow control installed in a readily accessible and visible location; the total fixture capacity served by a hydromechanical interceptor cannot exceed two and one‑half times the interceptor’s certified gpm rating per § 1014.2 and § 1014.2.1. Gravity grease interceptors are designed and sized by volume using drainage fixture units (DFUs) (30‑minute retention) and must meet the design/installation provisions in § 1014.3.1 and the sizing table in § 1014.3.6. All requirements below are drawn from those controlling sections of the California Plumbing Code.

Hydromechanical devices control flow with a vented orifice upstream and are sized by flow rate; gravity interceptors are sized by required retention volume (DFUs → gallons) and provide 30‑minute retention.

Requirements in detail

Key defined terms (first use bolded)

Hydromechanical Grease Interceptor (HGI) — identified by flow rate and separation efficiency; design can include external vented flow control; typically installed indoors. § 1014.2.
Gravity Grease Interceptor (GGI) — identified by volume, 30‑minute retention, baffles, and minimum two compartments; generally installed outdoors. § 1014.3.1.
Vented Flow Control Device — an orifice/control with an air intake (vent) that limits flow into an HGI. See the HGI provisions in § 1014.2.

Sizing — decision‑relevant numbers

Use the table(s) below to choose between hydromechanical sizing (flow‑rate based) and gravity sizing (DFU → volume).

Parameter / decision point	Typical code value(s)	Code Reference
HGI allowed fixture capacity	Not to exceed 2.5 × certified gpm of the interceptor	§ 1014.2.1
HGI sizing by grease waste pipe (examples from Table 1014.2.1)	2" → 20 gpm (one‑minute 20 gpm / two‑minute 10 gpm); 3" → 60 gpm (one‑minute 75 gpm / two‑minute 35 gpm); 6" → 375 gpm (one‑minute 400 gpm / two‑minute 200 gpm)	§ 1014.2.1 / Table 1014.2.1
GGI required retention time	30 minutes	§ 1014.3.6
GGI sizing (selected DFUs → interceptor volume)	8 DFU → 500 gal, 21 DFU → 750 gal, 35 DFU → 1000 gal, 90 DFU → 1250 gal, 172 DFU → 1500 gal (full table in Table 1014.3.6)	§ 1014.3.6 / Table 1014.3.6
Minimum GGI characteristics	Two or more compartments, baffles, site‑approved construction meeting Chapter 17 or Authority Having Jurisdiction design	§ 1014.3.1 / § 1014.3.3

Notes: Table 1014.2.1 provides both one‑minute and two‑minute drainage periods for HGI sizing and uses full‑pipe gravity flow rates for the connected grease waste pipe; Table 1014.3.6 maps DFUs to required GGI volumes (rounded to nominal volumes).

Flow controls (hydromechanical)

HGIs served by fixtures/equipment must discharge through an approved vented flow control located in an accessible, visible location and sized so the total flow through the control never exceeds the interceptor’s rated flow. § 1014.2.
No adjustable or removable parts in the flow control are permitted (i.e., fixed orifice/approved listed devices only). § 1014.2.
The vent or air inlet for the flow control must connect to the sanitary drainage vent system or terminate through the roof — it must not open to the building interior. Also, no system vent shall lie between the flow control and the interceptor inlet. § 1014.2.
Exception: Listed grease interceptors with integral flow controls may be installed per manufacturer instructions (they are allowed in lieu of external vented flow controls). § 1014.2.

Venting (general)

HGIs: require an upstream vented flow control and a downstream vent installation in accordance with code (downstream venting for HGIs is required). See § 1014.2 and § 1014.2.2.
Gravity interceptors: are conventional plumbing appurtenances that must be installed and vented per the general drainage/venting provisions; each fixture discharging to an interceptor must be individually trapped and vented (see general provisions in Chapter 10 / § 1014.1.1). § 1014.3.1 and § 1014.1.1.

Exceptions & special cases

Listed HGIs that include integral flow controls are handled per the manufacturer’s installation instructions and are exempt from the external flow control requirement. § 1014.2 (Exception).
The Authority Having Jurisdiction may approve combinations of hydromechanical, gravity, and engineered systems to meet constraints of existing buildings or space limitations; design approval is required. § 1014.1.
Food waste disposers and dishwashers: prohibited from discharging into a grease interceptor unless the interceptor is specifically designed to receive that waste; otherwise, disposers may discharge directly to the building drainage system. § 1014.1.3.

If a fixture or appliance has no DFU assignment, gravity interceptor sizing may be based on the known flow rate (gpm × 30 minutes) per notes to Table 1014.3.6. § 1014.3.6.

Common mistakes

Installing an HGI without a properly vented flow control or with an adjustable/removable orifice (violates § 1014.2).
Oversizing HGI use by plumbing more fixture capacity than 2.5 × certified gpm (failure to apply § 1014.2.1).
Sizing a gravity interceptor by eyeballing instead of using Table 1014.3.6 (DFU → volume) or failing to use DFU limits where DFUs are known (§ 1014.3.6).
Placing the vented flow control so a system vent lies between it and the interceptor inlet (prohibited by § 1014.2).
Connecting toilets, urinals, or similar fixtures to a grease interceptor (prohibited). § 1014.3.2.1 / § 1014.1.3.

Worked example — concrete scenario

Scenario A — Hydromechanical interceptor for a pot‑and‑pan sink bank:

You select an HGI model certified at 40 gpm. Per § 1014.2.1, the total fixture capacity discharging into that HGI must not exceed 2.5 × 40 gpm = 100 gallons (total capacity volume of fixtures expressed in gallons using the fixture capacity method). § 1014.2.1 shows how to compute fixture flow (volume × 0.75 fill factor ÷ drain period of 1 or 2 minutes) and compare to the certified gpm and Table 1014.2.1.
Install an approved vented flow control sized so the flow through it ≤ 40 gpm, with its air inlet connected to the sanitary vent system and no intervening system vent between the control and the HGI inlet. § 1014.2.

Scenario B — Gravity interceptor for a small restaurant kitchen:

Count DFUs on the kitchen drain line (example in code: 12 DFU for certain fixtures). Using Table 1014.3.6, 12 DFU falls between 8 and 21; the table example selects a 750‑gallon interceptor for a similar 12‑DFU kitchen. § 1014.3.6 (example).

(Use the exact table values and example procedures from § 1014.2.1 and § 1014.3.6 when doing your field calcs.)

Common installation/inspection checklist (quick)

HGI: Verify certified gpm and compute allowed fixture capacity per § 1014.2.1.
HGI: Confirm flow control is vented, fixed (non‑adjustable), accessible, and no intervening vent exists. § 1014.2.
GGI: Confirm DFU count and select volume from Table 1014.3.6; verify baffles/compartments and access. § 1014.3.6 / § 1014.3.5.

Related provisions

§ 1014.1 — General grease interceptor provisions and approved standards.
§ 1014.1.1 — Each fixture discharging to an interceptor shall be individually trapped and vented.
§ 1014.2.2 — Vent downstream of hydromechanical interceptors.
Table 1014.2.1 — Hydromechanical sizing using gravity flow rates.
Table 1014.3.6 — Gravity grease interceptor sizing (DFU → volume).

Code references

Grounded in the retrieved California Plumbing Code — click a citation to read the verbatim passage:

CPC § 1014.2.1 High 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)2	SIZE OF GREASE INTERCEPTOR	Col4
DIAMETER OF GREASE WASTE PIPE (inches)	MAXIMUM FULL PIPE FLOW (gpm)2	ONE-MINUTE DRAINAGE PERIOD (gpm)	TWO-MINUTE DRAINAGE PERIOD (gpm)
2	20	20	10
3	60	75	35
4	125	150	75
5	230	250	125
6	375	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 High 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- MENTS	LOAD (gallons)	SIZE OF GREASE INTERCEPTOR ONE-MINUTE DRAINAGE PERIOD (gpm)	TWO- MINUTE DRAINAGE PERIOD (gpm)
Compartment size	––	––	––	––
24 inches x 24 inches x 12 inches	2	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

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 § 1011.0 High 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 § 1014.1.1 High relevance — show source text
2025 CALIFORNIA PLUMBING CODE 197

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TRAPS AND INTERCEPTORS

1014.1.1 Trapped and Vented. Each fixture discharging into a grease interceptor shall be individually trapped and vented in an approved manner.

1014.1.2 Maintenance. Grease interceptors shall be maintained in efficient operating condition by periodic removal of the accumulated grease and latent material. No such collected grease shall be introduced into drainage piping or a public or private sewer. Where the Authority Having Jurisdiction determines that a grease interceptor is not being properly cleaned or maintained, the Authority Having Jurisdiction shall have the authority to mandate the installation of additional equipment or devices and to mandate a maintenance program.

1014.1.3 Food Waste Disposers and Dishwash- ers. No food waste disposer or dishwasher shall be connected to or discharge into a grease interceptor. Commercial food waste disposers shall be permitted to discharge directly into the building’s drainage system.

Exception: Food waste disposers shall be permitted to discharge to grease interceptors that are designed to receive the discharge of food waste.

1014.2 Hydromechanical Grease Interceptors. Plumbing fixtures or equipment connected to a Type A and B hydromechanical grease interceptor shall discharge through an approved type of vented flow control installed in a readily accessible and visible location. Flow control devices shall be

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]
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

2025 CALIFORNIA PLUMBING CODE xxxvii

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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 § 3.3.68.4 Medium relevance — show source text
Minimal Sedation (Anxiolysis). A drug-induced state during which patients respond normally to verbal commands. Although cognitive function and coordination may be impaired, ventilatory and cardiovascular functions are unaffected. [NFPA 99:3.3.68.4]

Moderate Sedation/Analgesia (Conscious Seda- tion). A drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation. No interventions are required to maintain a patient airway, and spontaneous ventilation is adequate. Cardiovascular function is usually maintained. [NFPA 99:3.3.68.3]

Grade. The slope or fall of a line of pipe in reference to a horizontal plane. In drainage, it is usually expressed as the fall in a fraction of an inch (mm) or percentage slope per foot (meter) length of pipe.

Gravity Grease Interceptor. A plumbing appurtenance or appliance that is installed in a sanitary drainage system to intercept nonpetroleum fats, oils, and greases (FOG) from a wastewater discharge and is identified by volume, 30 minute retention time, baffle(s), not less than two compartments, a total volume of not less than 300 gallons (1135 L), and gravity separation. [These interceptors comply with the requirements of Chapter 10 or are designed by a registered design professional.] Gravity grease interceptors are generally installed outside.

Graywater. [BSC-CG & HCD 1] Pursuant to Health and Safety Code Section 17922.12, “graywater” means untreated wastewater that has not been contaminated by any toilet dis- charge, has not been affected by infectious, contaminated, or unhealthy bodily wastes, and does not present a threat from contamination by unhealthful processing, manufacturing, or operating wastes. "Graywater" includes, but is not limited to, wastewater from bathtubs, showers, bathroom washbasins, clothes washing machines, and laundry tubs, but does not include wastewater from kitchen sinks or dishwashers.

Note: For the purpose of applying the standards contained in this code, “Graywater” as defined above, has the same meaning as “gray water”, “grey water”, and “greywater”.

Gray Water System. [BSC-CG & HCD 1] A system designed to collect gray water on-site for reuse or distribution to an irrigation or disposal field. A gray water system may include, on-site treated nonpotable water devices or equip- ment, tanks, valves, filters, pumps or other appurtenances along with piping and receiving landscape.

Grease Interceptor. A plumbing appurtenance or appliance that is installed in a sanitary drainage system to intercept nonpetroleum fats, oil, and greases (FOG) from a wastewater discharge.

Grease Removal Device (GRD). A hydromechanical grease interceptor that automatically, mechanically removes non-petroleum fats, oils and grease (FOG) from the interceptor, the control of which are either automatic or manually initiated.

Grounding Electrode. A conducting object through which a direct connection to earth is established. [NFPA 70:100 (Part I)]

Groundwater. Water that exists beneath the earth’s surface.
CPC § 3.3.74 Medium relevance — show source text
a. Shall be designed and installed to prevent splashing outside of the lavatory.

b. Shall be well-fitted and sealed to prevent water leaks onto or into the cabinetry or wall spaces.

c. Design of lavatories and cabinetry shall not permit storage beneath the fixture basin.

d. Shall be constructed of nonporous material. Hangers. See Supports. Health Care Facility’s Governing Body. The person or persons who have the overall legal responsibility for the operation of a health care facility. [NFPA 99:3.3.74] High Hazard. See Contamination. Horizontal Branch. A drainpipe extending laterally from soil or waste stack or building drain with or without vertical sections or branches, which receives the discharge from one or more fixture drains and conducts it to the soil or waste stack or the building drain. Horizontal Pipe. A pipe or fitting that is installed in a horizontal position or which makes an angle of less than 45 degrees (0.79 rad) with the horizontal.

Hot Water. Water at a temperature exceeding or equal to 120°F (49°C). House Drain. See Building Drain. House Sewer. See Building Sewer. Hydromechanical Grease Interceptor. A plumbing appurtenance or appliance that is installed in a sanitary drainage system to intercept nonpetroleum fats, oil, and

grease (FOG) from a wastewater discharge and is identified by flow rate, and separation and retention efficiency. The design incorporates air entrainment, hydromechanical separation, interior baffling, or barriers in combination or separately, and one of the following:

(1) External flow control, with an air intake (vent), directly connected.

(2) External flow control, without air intake (vent), directly connected.

(3) Without external flow control, directly connected.

(4) Without external flow control, indirectly connected.

These interceptors comply with the requirements of Table 1014.2.1. Hydromechanical grease interceptors are generally installed inside.

211.0 – I –

Indirect-Fired Water Heater. A water heater consisting of a storage tank equipped with an internal or external heat exchanger used to transfer heat from an external source to heat potable water. The storage tank either contains heated potable water or water supplied from an external source, such as a boiler.

Indirect Waste Pipe. A pipe that does not connect directly to the drainage system but conveys liquid wastes by discharging into a plumbing fixture, interceptor, or receptacle that is directly connected to the drainage system.

Individual Vent. A pipe installed to vent a fixture trap, and that connects with the vent system above the fixture served or terminates in the open air.

Industrial Waste. Liquid or water-borne waste from industrial or commercial processes, except domestic sewage.

Insanitary. A condition that is contrary to sanitary principles or is injurious to health.

Conditions to which “insanitary” shall apply include the following:

(1) A trap that does not maintain a proper trap seal.

(2) An opening in a drainage system, except where lawful that is not provided with an approved liquid-sealed trap.

(3) A plumbing fixture or other waste discharging receptor or device that is not supplied with water sufficient to flush and maintain the fixture or receptor in a clean condition.

(4) A defective fixture, trap, pipe, or fitting.
CPC § 1014.3.6 Medium relevance — show source text
1014.3.6, shall be installed in accordance with the manufacturer’s installation instructions to receive the drainage from fixtures or equipment that produce grease-laden waste. Grease-laden waste fixtures shall include, but not be limited to, sinks and drains, such as floor drains, floor sinks, and other fixtures or equipment in serving establishments, such as restaurants, cafes, lunch counters, cafeterias, bars and clubs, hotels, hospitals, sanitariums, factory or school kitchens, or other establishments where grease is introduced into the drainage or sewage system in quantities that can effect line stoppage or hinder sewage treatment or private sewage disposal systems. A combination of hydromechanical, gravity grease interceptors and engineered systems shall be allowed to meet this code and other applicable requirements of the Authority Having Jurisdiction where space or existing physical constraints of existing buildings necessitate such installations. A grease interceptor shall not be required for individual dwelling units or private living quarters. Water closets, urinals, and other plumbing fixtures conveying human waste shall not drain into or through the grease interceptor.

1014.1A [OSHPD 1, 1R, 2, 3, 4 & 5] The Authority Having Jurisdiction is the individual official, board, department or agency authorized to administer and enforce the sewage treatment system in the area of the location of the health facil- ity.

1014.1B [OSHPD 1, 1R, 2, 3, 4 & 5] Grease interceptors shall not be installed in food preparation area of the kitchens.

1014.1C [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.

2025 CALIFORNIA PLUMBING CODE 197

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TRAPS AND INTERCEPTORS

1014.1.1 Trapped and Vented. Each fixture discharging into a grease interceptor shall be individually trapped and vented in an approved manner.

1014.1.2 Maintenance. Grease interceptors shall be maintained in efficient operating condition by periodic removal of the accumulated grease and latent material. No such collected grease shall be introduced into drainage piping or a public or private sewer. Where the Authority Having Jurisdiction determines that a grease interceptor is not being properly cleaned or maintained, the Authority Having Jurisdiction shall have the authority to mandate the installation of additional equipment or devices and to mandate a maintenance program.

1014.1.3 Food Waste Disposers and Dishwash- ers. No food waste disposer or dishwasher shall be connected to or discharge into a grease interceptor. Commercial food waste disposers shall be permitted to discharge directly into the building’s drainage system.

Exception: Food waste disposers shall be permitted to discharge to grease interceptors that are designed to receive the discharge of food waste.

1014.2 Hydromechanical Grease Interceptors. Plumbing fixtures or equipment connected to a Type A and B hydromechanical grease interceptor shall discharge through an approved type of vented flow control installed in a readily accessible and visible location. Flow control devices shall be
CPC § 3.785 Medium relevance — show source text
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.

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.

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)
8	500
21	750
35	1000
90	1250
172	1500
216	2000
307	2500
342	3000
428	4000
576	5000
720	7500
2112	10 000
2640	15 000

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 § 1503.0 Medium relevance — show source text
Gray water systems . . . . . . . . . . . . . . . . . . . . . . .1503.0 Inspection and testing . . . . . . . . . . . . . . . . . . . . .1502.0 Operation and maintenance manual . . . . . . . . . .1501.6 GREASE INTERCEPTORS . . . . . .1014.0, 1014.1B, 1014.1C

Approved standards . . . . . . . . . . . . . . . . . . . . . . .1014.1

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209.0

Capacity . . . . . . . . . . . . . . . . . .1014.2.1, Table 1014.2.1 Gravity-type . . . . . . . . . . . . . . . . .1014.3, Table 1014.3.6 Hydromechanical-type . . . . . . . . . . . . . . . . . . . . .1014.2 Not required . . . . . . . . . . . . . . . . . . . . . . . . . . . .1014.1.3 Required . . . . . . . . . . . . . . . . . .1010.1, 1014.1, H 101.3

GRINDER PUMPS . . . . . . . . . . . . . . . . . . . . . . . . . . .710.12

GROUNDWATER, DEFINITION . . . . . . . . . . . . . . . . . .209.0

– H –

HANDHELD SHOWERS . . . . . . . . . . . . . . . . . . . . . . . .417.3

HANDWASHING FIXTURE

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210.0

HANGERS . . . . . . . . . . . . . . . . . . . . . . . . . . .(see Supports) HARMFUL WASTES . . . . . . . . . . . . . . . . . . . .(see Wastes, detrimental or harmful) HEALTH AND SAFETY . . . . . . . . . . . . . . . . . . .101.3, 102.5

HEALTH FACILITIES AND CLINICS,

WATER DISTRIBUTION . . . . . . . . . . . . . . . . . . . . . .613.0

HEAT EXCHANGERS . . . . . . . . . . . . . . . . . . . . . . .505.4.1,

603.5.4, C 302.0

HEAT-FUSION JOINTS . . . . . . . . . . . . . . . . .212.0, 605.6.1,

605.11.1, 1208.5.10.2

HORIZONTAL BRANCH,
CPC § 1010.5.2 Medium relevance — show source text
1010.5.2 Sewage and Plant Waste. The sewer sys- tem have adequate slope and capacity to remove readily all waste from the various processing operations and to minimize, or if possible, prevent stoppage and surcharg- ing of the system. When the sewage disposal system is a private system which is required to be approved by a state or local health authority, the applicant shall fur- nish the administrator a letter from the proper health authority indicating that the sewage disposal system is acceptable to such authority.

1011.0 Minimum Requirements for Auto Wash Racks.

1011.1 General. A private or public wash rack or floor or slab used for cleaning machinery or machine parts shall be adequately protected against storm or surface water and shall drain or discharge into an approved interceptor (clarifier).

1012.0 Commercial and Industrial Laundries.

1012.1 General. Laundry equipment in commercial and industrial buildings that do not have integral strainers shall discharge into an interceptor having a wire basket or similar device that is removable for cleaning and that will prevent passage into the drainage system of solids [1] ⁄ 2 of an inch (12.7 mm) or larger in maximum dimensions, such as string, rags, buttons, or other solid materials detrimental to the public sewerage system.

1013.0 Bottling Establishments.

1013.1 General. Bottling plants shall discharge their process wastes into an interceptor that will provide for the separation of broken glass or other solids, before discharging liquid wastes into the drainage system.

1014.0 Grease Interceptors.

1014.1 General. Where it is determined by the Authority Having Jurisdiction that waste pretreatment is required, an approved type of grease interceptor(s) shall comply with ASME A112.14.3, ASME A112.14.4, CSA B481, ANSI/CAN/IAPMO Z1001, PDI G-101, or PDI G-102, and sized in accordance with Section 1014.2.1 or Section

1014.3.6, shall be installed in accordance with the manufacturer’s installation instructions to receive the drainage from fixtures or equipment that produce grease-laden waste. Grease-laden waste fixtures shall include, but not be limited to, sinks and drains, such as floor drains, floor sinks, and other fixtures or equipment in serving establishments, such as restaurants, cafes, lunch counters, cafeterias, bars and clubs, hotels, hospitals, sanitariums, factory or school kitchens, or other establishments where grease is introduced into the drainage or sewage system in quantities that can effect line stoppage or hinder sewage treatment or private sewage disposal systems. A combination of hydromechanical, gravity grease interceptors and engineered systems shall be allowed to meet this code and other applicable requirements of the Authority Having Jurisdiction where space or existing physical constraints of existing buildings necessitate such installations. A grease interceptor shall not be required for individual dwelling units or private living quarters. Water closets, urinals, and other plumbing fixtures conveying human waste shall not drain into or through the grease interceptor.

1014.1A [OSHPD 1, 1R, 2, 3, 4 & 5] The Authority Having Jurisdiction is the individual official, board, department or agency authorized to administer and enforce the sewage treatment system in the area of the location of the health facil- ity.

Frequently asked questions

What determines whether I can use a hydromechanical or gravity interceptor?

Choice is driven by space and hydraulic needs: HGIs are flow‑rated and compact (used where indoor space and flow‑control are practical) while GGIs are volumetric, require larger outdoor space and provide 30‑minute retention. Confirm applicability and sizing using § 1014.2 / § 1014.2.1 for HGIs and § 1014.3.6 / § 1014.3.1 for GGIs.

Do I have to vent the flow control for an HGI to the roof?

The flow control’s air inlet must connect to the sanitary vent system or terminate through the roof — it must not terminate to the free atmosphere inside the building; also, there must be no system vent between the control and the interceptor inlet. See § 1014.2.

Can I connect a dishwasher or garbage disposer to an interceptor?

Dishwashers and food waste disposers are not permitted to discharge into a grease interceptor unless the interceptor is specifically designed to receive their discharge; otherwise disposers may discharge directly to the drainage system. See § 1014.1.3.

How do I size an HGI when pipe diameter and DFUs are both available?

HGIs are sized by flow (use Table 1014.2.1 or fixture capacity method of § 1014.2.1); gravity interceptors use DFUs → volume (Table 1014.3.6). Use the method appropriate to the interceptor type being installed.

What if I don’t know DFUs for a fixture?

If DFUs are unknown for directly connected fixtures/appliances, gravity interceptor sizing may be based on the known flow rate multiplied by 30 minutes (see notes to Table 1014.3.6).

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