4.3 Oil Separators, Sand & Lint Interceptors, Other Interceptors & Corrosive Waste

General interceptor rules

• 1003.1: interceptors and separators are required to keep oil, grease, sand and other harmful substances out of the public sewer, private sewage systems and treatment plants.
• 1003.2: size, type and location follow the manufacturer's instructions and the code. Wastes that do not need treatment must not enter an interceptor.
• 1003.9: interceptors and separators must be designed so they do not become air-bound, and they are vented by one of the methods in Chapter 9.
• 1003.10: each interceptor needs access for service, and must be maintained by periodically removing grease, scum, oil, floating substances and solids.

Oil separators (IPC 1003.4)

Where required: at repair garages where floor or trench drains are provided, at car washing facilities, at factories where oily and flammable liquid wastes are produced, and in hydraulic elevator pits. Oil-bearing, grease-bearing or flammable wastes discharge into the separator before reaching the building drainage system.

Exception: an oil separator is not required in a hydraulic elevator pit with an approved alarm system. The alarm must not shut down pumps needed for firefighters' emergency operation of the elevator.

1003.4.1: a mixture of light and heavy liquids with different specific gravities must be separated in an approved receptacle.

1003.4.2 design: oil separators must be listed and labeled, or designed to 1003.4.2.1 and 1003.4.2.2:

• 1003.4.2.1: a depth of at least 2 feet below the invert of the discharge drain, and an outlet with a water seal of at least 18 inches.
• 1003.4.2.2: where automobiles are serviced, greased, repaired or washed, or where gasoline is dispensed, capacity of at least 6 cubic feet for the first 100 square feet of area drained, plus 1 cubic foot for each additional 100 square feet.
• Parking garages without servicing, repairing, washing or gasoline dispensing do not need a separator. Areas of commercial garages used only for vehicle storage need not drain through one.

$$V_{\text{cu ft}} = 6 + \frac{A - 100}{100}$$

Worked example: a 1,500 sq ft service bay drains to an oil separator. V = 6 + (1,400 ÷ 100) = 20 cubic feet, which is about 150 gallons at 7.48 gallons per cubic foot.

The IPC sends you to Chapter 9 for venting oil separators. Do not apply a "two independent 2-inch vents" rule from other codes as a 2021 IPC requirement.

Sand and heavy-solids interceptors (IPC 1003.5)

Sand and similar interceptors for heavy solids in commercial establishments must be designed and located with ready access for cleaning, and must have a water seal of at least 6 inches. Typical uses are vehicle wash bays, some shops, and similar facilities that wash grit into floor drains.

Clothes washer, bottling and slaughterhouse interceptors

• 1003.6 Clothes washers: must discharge through an interceptor with a removable wire basket or similar device that stops solids 1/2 inch or larger, string, rags, buttons and other harmful material. Exceptions: clothes washers in individual dwelling units, and a single residential-type washer installed outside a dwelling unit.
• 1003.7 Bottling establishments: process wastes discharge into an interceptor that separates broken glass and other solids.
• 1003.8 Slaughterhouses: slaughtering-room and dressing-room drains need separators that keep feathers, entrails and other clogging materials out of the drainage system.

Corrosive and chemical waste (IPC 702.6, 803 and 901.3)

• 803.1: corrosive liquids, spent acids or other harmful chemicals that would damage a drain, sewer, soil or waste pipe, produce noxious or toxic fumes, or interfere with sewage treatment must not enter the plumbing system unless thoroughly diluted, neutralized or treated by an approved dilution or neutralizing device. The device must be automatically supplied with enough diluting water or neutralizing medium. The nature of the waste and the treatment method must be approved before installation.
• 803.2: a chemical drainage and vent system must be designed and installed to the code and completely separated from the sanitary systems. Chemical waste may not discharge to a sanitary drainage system until it is treated under 803.1.
• 702.6: a chemical waste system must be completely separate from the sanitary drainage system. Its separate drainage and vent piping must be approved material resistant to corrosion and degradation for the chemicals and concentrations involved.
• 901.3: the chemical waste vent system must be independent of the sanitary vent system. It terminates separately through the roof, or at an ASSE 1049 air admittance valve made of approved chemical-resistant material and tested to ASTM F1412.
• 1002.9: an underground acid-resisting trap of brittleware is embedded in concrete extending 6 inches beyond its bottom and sides.
• 1002.3 exception: a drum trap may serve a chemical waste system.

Choosing materials

The code does not name specific chemical-resistant pipe. It requires material suited to the chemicals and concentrations. Common choices for laboratory acid waste include polypropylene, PVDF, borosilicate glass and high-silicon cast iron. Above-ground drainage Table 702.1 lists glass pipe (ASTM C1053), polyolefin pipe (ASTM F1412) and PVDF pipe (ASTM F1673). Ordinary PVC DWV may not be suitable for strong acids at high concentration.

How neutralizing tanks work

Many laboratory systems pass acid waste through a tank packed with limestone (calcium carbonate) chips. The acid reacts with the stone to form a salt, water and carbon dioxide. The tank needs a vent for the CO₂, access for replacing spent stone, and monitoring of effluent pH. The chip specification, tank size and discharge pH limit come from the manufacturer, the design engineer and the sewer authority, not from the IPC.

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