14.3 Gasoline, Oil & Sand Separators

14.3 Gasoline, Oil & Sand Separators

Quick Answer: If a Massachusetts building can take a motor vehicle — parking, repair, wash, storage, or any space large enough for vehicle access — 248 CMR 10.09(1)(a) wants a separation or containment system unless a listed exception applies. Sewer connected: Example 2 precast separator, Product-accepted separator, or Massachusetts PE design, sized 6 cubic feet for the first 100 square feet drained plus 1 cubic foot per additional 100 square feet. Not sewer connected: the two-bay holding tank in 14.2. Vents for petroleum floor drains stay off the sanitary DWV; separator chamber and outlet vents are 4 inch, back inside, independently through the roof, and labeled. Sand interceptors have a 6-inch minimum water seal and a basket. Open Cornell 10.09; do not import IPC garage-separator gallons.

This is the third PSI written item in the five-item separators cluster (October 3, 2025 CIB: Gasoline, Oil, and Sand Separators). Independent OpenExamPrep teaching uses 248 CMR 10.09 (12/8/2023), the Mass.gov Gas/Oil Separator Alternative policy, and 360 CMR 10.016 when the site is MWRA. It is not a Board publication.

Motor vehicle (10.09(1)(a) note). A self-propelled road vehicle, commonly wheeled, including cars, buses, trucks, and tractors. A riding mower in a garden shed is not that note; a box truck through an overhead door is.

Where separators are required — and the exceptions the exam loves

Required (10.09(1)(a)1) for any building or structure containing:

1. Motor vehicle parking, repair/maintenance, washing, and storage areas; or
2. Other spaces sufficiently large enough to allow access by motor vehicles.

Exceptions — a separation or containment system shall not be required for:

Scenario. A Worcester warehouse has an overhead door a van could enter, but bollards 48 inches on center stand outside that door and there is no parking, repair, or wash inside. Exception vi applies. Move the bollards to 8 feet apart “so the forklift can sneak through” and the exception dies. A seven-car condo garage is not exception ii.

Older Board interpretations about overhead doors still circulate on municipal sites. Teach the current exception list. The 05-29-2013 alternative-method policy is a holding-tank variance path (14.2), not a sixth unlabeled exception you skip filing for.

Elevator pits (10.09(1)(a)1.c). Gravity drains or pumps that enter sanitary or storm shall comply with 248 CMR 10.00. Elevators that use hydraulic oil or other petroleum distillates harmful to sanitary or storm shall discharge through a properly sized oil/water separator installed to 10.09. Piping shall discharge into the building sanitary system, except: (1) storm if a local ordinance, bylaw, rule, or regulation allows it; (2) Product-accepted pumps with sensors that divert volatiles may be installed in lieu of a gas/oil separation system. Board minutes still show denied variances for elevator pumps that skip the separator when the elevator uses oil. The printed exceptions are local storm permission or a Product-accepted diverting pump — not “elevators never leak.”

Sewer-connected separators: size, build, and vent to the outdoor air

10.09(1)(a)2 — when connecting to a sewer, use one of:

1. A system meeting 10.09 Example 2 (or other Board-approved specifications);
2. A Product-accepted separation system;
3. A system designed by a Massachusetts professional engineer who prepares the plans and certifies in writing to the inspector that the installation matches those documents.

Other agencies may also have to sign (DEP 314 CMR 7.00 sewer connection; MWRA 360 CMR 10.016 when in that district). Those approvals do not supersede the plumbing permit or the inspector’s look at every component and connection. If another agency’s condition would violate 248 CMR, follow 248 CMR unless the Board grants a variance. MWRA notice of a new separator must be made before the plumbing permit.

Sizing (10.09(1)(a)5). Minimum volume six cubic feet for the first 100 square feet of area drained, plus one cubic foot for each additional 100 square feet. In excessive-flow areas, size from the manufacturer’s specifications. Sizing shall also follow the 10.09 Table that accompanies Example 2 (inlet-size geometry). Teach the cubic-foot formula on the closed-book exam; do not guess IPC “one cubic foot per vehicle” tables that 10.09 does not print.

Worked example. A Springfield repair shop drains 2,400 square feet to a sanitary gas/oil separator. First 100 sq ft → 6 cu ft. Remaining 2,300 sq ft → 23 × 1 = 23 cu ft. Total 29 cubic feet. If the wash bay dumps a fire-hose flow the manufacturer calls excessive, use that listing, not 29 cu ft as a ceiling.

Precast or built-in-place (10.09(1)(a)5.a / Example 2):

• Locate outside wherever possible; access cover minimum 24 inches diameter. Inside the building, the access cover must be sealed tight.
• Minimum inlet 4 inch; outlet equal to or greater than the inlet.
• Inlet invert not less than 4 inches above the water line.
• Chamber vent 4 inch, as close as possible to the top of the tank.
• Chamber and outlet vents 4 inch, returned to the inside of the building, extended independently through the roof.
• All venting associated with a gas/oil separator shall be labelled.
• Access ladder steps non-corrosive, spaced 18 inches apart.
• Precast: ASTM C-478, 4,000 PSI; joints butyl rubber ASTM C-990; penetrations sealed with hydraulic cement or C-990 butyl.
• Minimum liquid water seal depth 3 feet.
• Outlet pipe to tank base minimum 2 feet 6 inches.
• Fill with water and test before service.
• Piping extra heavy, service weight, and no-hub cast iron.
• Storm separator discharge may go to the building storm drain or storm sewer. Sanitary separator discharge may go to the building sanitary drain or sanitary sewer. Do not cross those two.

Floor- and trough-drain vents (10.09(1)(a)4). Vents for drains that convey waste from all gas, oil, and other petroleum distillate separation or containment systems shall be independent of the sanitary DWV systems. They may connect to the chamber vent of the separator or containment system no less than 6 inches above the flood-level rim of the floor/trough drain. Open-parking-garage trap exceptions, when they apply, are the 10.09 cross-reference to the trap section — do not invent a “no trap in any garage” slogan.

Fire-code coordination as 10.09 states it. The 12/8/2023 plumbing text does not reprint a 527 CMR or NFPA 30 section number inside 10.09. What it does print for flammable waste is: tanks and pumps rated for volatile chemicals, independent labeled vents, through-roof terminations, no mixing of those vents with ordinary sanitary vents, and no wastes into the separator except those that need separation. Local fire-prevention officers still enforce 527 CMR 1.00; do not invent setback distances 10.09 never wrote. If a stem asks how the plumbing code keeps gasoline vapor out of the toilet stack, the answer is 10.09(1)(a)4 independent vents, not an IPC air-admittance valve.

Sand interceptors, special-use units, and the Board alternative PDF

Special-use interceptors and separators (10.09(1)(c)) sit beside the gas/oil recipe. Install individual fixture traps when the special-use device does not meet 10.08(2)(d) and (e). Commercial establishments include, but are not limited to:

• Repair garages
• Laundries
• Bottling facilities
• Slaughterhouses
• Other facilities where harmful or hazardous products may enter the building drainage system

Special-use interceptors shall be readily accessible for cleaning and shall have a wire or sand basket capable of stopping sand or solids likely to clog the drain. Sand interceptors shall have a water seal of not less than six inches. That 6-inch sand seal is not the 3-foot liquid seal on a precast gas/oil tank. Mixing those two numbers is a classic wrong answer.

Repair-garage overlap. A service bay needs the 10.09(1)(a) gas/oil system and the special-use/sand hardware the solids require. A laundry that never sees motor oil still needs the special-use interceptor 10.09(1)(c) names; it does not automatically need a 29-cubic-foot gasoline separator.

Board alternative method (Mass.gov PDF, enacted 05-29-2013). When the job is maximum two vehicles/bays and the applicant wants the drawn double-wall tank + 75 percent alarm instead of Example 2, that is the variance path taught in 14.2 — not a silent substitute for a 40-car parking garage separator. Open the PDF; memorize the criteria list; do not apply 60 gallons per vehicle to a 200-stall deck.

MWRA / local overlays. 360 CMR 10.016 still wants gas/oil separators in MWRA territory for garages, parking lots, and petroleum-handling wastes, and says those separators shall also conform to 248 CMR 10.00. Passing a plumbing final does not waive MWRA inspection-before-backfill. Taunton-style local pumping schedules (monthly inspect, annual pump) are health-department overlays, not 10.09 Table 2.

Scenario. A Cambridge parking garage (open deck) drains vehicle areas to a storm separator because the discharge is storm water with petroleum sheen; 10.09(1)(a)5.a.xvii allows storm-separator discharge to the storm drain. The chamber and outlet vents still return inside and go independently through the roof, labeled. Tying those vents to the restroom stack because “they all go to air” fails 10.09(1)(a)4 and 5.a.v–vi.

Official resources

• 248 CMR 10.09 (Cornell LII) — required locations, exceptions, Example 2, vents, sand seal
• Separation or Containment of Gas, Oil, and Other Petroleum Distillates (UpCodes) — HTML 10.09(1)(a)
• Gas/Oil Separator Alternative (Mass.gov PDF) — 05-29-2013 two-bay variance method
• 360 CMR 10.016 Gas/Oil Separators (Mass.gov) — MWRA overlay; still must meet 248 CMR 10.00
• 314 CMR 7.00 Sewer System Connection (Mass.gov) — named in 10.09(1)(a)2
• 248 CMR 10.00 (Mass.gov, effective 12/8/2023) — official PDF