Grease Interceptor Service and Manifest

Purpose

The regulated product of a grease interceptor service is the manifest, not the pump-out. A municipality that inspects a restaurant reads paperwork, and a manifest signed over a partial evacuation is a false document the restaurant relies on. This procedure guarantees that the accumulation is measured before anything is removed, that the unit is fully evacuated rather than skimmed, and that the manifest states a volume the interceptor could actually have held. It also guarantees the accumulation number gets used, because the point of measuring is to set the next interval rather than to keep running the one on the contract.

Scope

Covers routine and complaint-driven service of hydromechanical grease interceptors under sinks and exterior gravity interceptors at small restaurants, cafes, bars, delis and shared kitchens: measurement, evacuation, internals inspection, refill, manifest and interval setting.

Does not cover sizing or selection, owned by the grease interceptor sizing reference, which is also where the 25 percent rule is defined and which this procedure applies rather than re-derives. Does not cover kitchen branch line cleaning, owned by the hydro jetting service standard. Does not cover any entry into the interceptor, which is prohibited by this procedure outright and belongs to a permit-required confined space crew.

Roles and responsibilities

Procedure

1. Confirm before the truck moves that this is a full evacuation, and that the hauler's permit covers this jurisdiction. Acceptance: the work order says full pump-out with wall wash, and the hauler permit number and expiry are on the ticket. Wrong looks like a skim priced as a service, which leaves the solids bed in place and makes the next measurement meaningless. Stop rule: an expired or missing permit stops the job before a lid moves, because an unpermitted disposal makes the restaurant's manifest worthless. Hazard: none at this step, it is a phone call, but a job booked without the closed-hours window puts an open interceptor beside a working kitchen.

2. Set the work zone and stop the discharge before any lid comes off. Cone the area, control traffic around an exterior unit, and have the kitchen shut down sinks, dishwasher and wok station. Acceptance: no discharge for the duration, confirmed with the manager, behind a barrier no vehicle or pedestrian can reach an open lid past. Wrong looks like an open interceptor in a live delivery lane. Stop rule: if the kitchen cannot stop discharge, the service does not start, because a unit pumped while running was never emptied. Hazard: an open interceptor is a fall-into-open-vault exposure nobody expects, so the barrier goes up before the lid is cracked and a lid never sits loose over its own opening.

3. Test the atmosphere before the lid is fully open, keep the meter running, and nobody enters. Crack the lid from upwind and drop a four-gas meter into the headspace. Acceptance: readings logged, the meter running continuously in the breathing zone through the whole job, everyone upwind. Wrong looks like one reading at the start treated as an all-clear, when pumping agitates the layers and liberates more sulfide than opening the lid ever did. Stop rule: at hydrogen sulfide approaching the 20 ppm ceiling OSHA sets at 29 CFR 1910.1000 Table Z-2, or combustible gas at 10 percent of the lower explosive limit, everyone withdraws upwind until it clears on the instrument; a space that stops smelling bad is olfactory fatigue, not a clear space. Hazard: this is a permit-required confined space under 29 CFR 1910.146, so nobody goes in for any reason, a dropped tool is written off, and entry is a permit crew with an attendant and supplied air.

4. Measure and record the accumulation before anything is removed. Use a sludge judge or a clear tube to read total wetted depth, the thickness of the floating FOG cap and the depth of the settled solids bed. Acceptance: three depths in inches, plus the combined FOG and solids as a percentage of wetted depth. Wrong looks like recording only that it was full, which cannot set an interval. Stop rule: combined FOG and solids at or above 25 percent of wetted depth means the current interval is too long and step 9 shortens it; that is a finding to report, not a routine result. Hazard: leaning over an open interceptor to sound it is the moment people fall in, so work from outside the lid opening on a stable stance with the meter still running and never straddle the opening.

5. Evacuate the whole unit, then wash the walls and baffles down and pull that out too. Acceptance: the hauler's hose reaches the floor of the tank in every compartment, the sidewalls are washed and the wash water removed, and the tank is visibly empty of the solids bed from outside. Wrong looks like the FOG cap and the top of the water gone with a solids bed left on the floor, which is the shape of every skim job and reads identically on an invoice. Stop rule: if the truck fills before the tank is empty, the tank is not returned to service part-emptied; the hauler makes a second trip and the manifest states both volumes. Hazard: a vacuum hose under load will move and can strike, so hands stay off the hose end while the pump is running, and the hauler owns the pump controls throughout.

6. Inspect the internals with a light from outside before the tank is refilled. Check the inlet and outlet tees or baffles, the flow control fitting on a hydromechanical unit, the sample port, the vent connection and the lid gasket. Acceptance: tees present and intact, sample port accessible, vent connected, lid seating on an unbroken gasket. Wrong looks like a missing outlet tee, which sends the FOG cap straight to the sewer however well the unit is maintained and cannot be seen once the tank is full. Stop rule: any missing or broken internal makes the unit non-conforming; complete the service, report it in writing the same day, and schedule the repair before the next inspection. Hazard: nothing goes past the lid opening but light and a camera, and the confined space rule from step 3 stands.

7. Refill with clean water to the outlet invert before the interceptor returns to service. Acceptance: water level standing at the outlet invert, confirmed by eye from outside, with the lid seated and secured. Wrong looks like an empty tank returned to service, which has no separation at all until it fills from kitchen flow, so the first hours of production go straight down the sewer. Stop rule: no refill water available means the unit does not go back into service and the kitchen holds discharge until it does. Hazard: this is the step that puts the system back, so the lid is seated and latched before anyone leaves the zone, the barrier stays up until it is, and the kitchen is told in person that it may discharge again rather than left to guess.

8. Complete the manifest on site with the hauler, before the truck leaves. Acceptance: generator name and site address, hauler company and permit number, date and time, volume removed in gallons, the receiving disposal facility, and signatures from hauler and kitchen manager. Wrong looks like a volume that exceeds the interceptor's rated capacity, or a manifest mailed later and never returned. Stop rule: an incomplete manifest is not a paperwork problem to fix at the office; it is corrected before the truck leaves, because the two signatures cannot be collected afterward. Hazard: none at this step, it is a form on a clipboard, and the shop's copy is scanned the same day so a lost original does not cost the restaurant its permit.

9. Set the next interval from the measured accumulation, not from the contract. Scale the current interval by the ratio of the 25 percent target to the measured percentage, then round down to the next standard interval you can schedule. Acceptance: a next-service date on the record with the arithmetic behind it written out. Wrong looks like leaving a quarterly cycle in place on a unit that measured over target, which guarantees the same finding next time. Stop rule: where the computed interval falls below what the account will accept, that is a sizing conversation for the lead and the sizing reference, not a scheduling one. Hazard: none at this step, it is arithmetic at the desk, and skipping it is how a restaurant gets a violation between two clean services.

The record this produces

Per service: unit type and rated capacity, wetted depth, FOG cap depth, solids depth, combined percentage, volume removed, hauler and permit number, disposal facility, internals condition with any deficiency named, refill confirmed, atmosphere readings, and the next interval with its derivation. The signed manifest is attached as an image, not summarised.

The kitchen manager keeps the manifest for whatever retention period the municipal FOG ordinance sets, commonly two to three years, and that number is the ordinance's rather than this procedure's. The next tech reads last service's combined percentage to know whether the interval is working. The lead reads the deficiency list, because a missing outlet tee found twice is a replacement, not a repair. The inspector reads the manifest chain, and a gap in it triggers the permit conversation.

One worked pass, including a failure

A 1,000 gallon exterior gravity interceptor behind a 60-seat restaurant, on a 90 day contract cycle, serviced at 7 am before opening. Step 2 cones the lane and the manager confirms the kitchen is dry. Step 3 reads 6 ppm hydrogen sulfide in the headspace on the crack, oxygen normal, combustible gas below 5 percent of the lower explosive limit; the meter stays in the breathing zone and reads 11 ppm during pumping, which is under the Table Z-2 ceiling, so work continues upwind with the readings logged.

Step 4: wetted depth 48 in, FOG cap 6 in, settled solids 8 in. 6 plus 8 is 14 in, and 14 divided by 48 is 29.2 percent, over the 25 percent trigger. The current interval is too long and step 9 will shorten it.

Step 6 fails. The outlet tee is broken off at the sanitary tee hub and lying on the floor of the outlet chamber, which is why the kitchen branch was jetted twice in the last year despite services on schedule. Stop rule taken: the pump-out completes, the manager gets it in writing that afternoon with a photo, and the tee replacement is scheduled ahead of the next FOG inspection rather than signed off as normal.

Step 7 refills to the outlet invert. Step 8 records 980 gal removed, under the unit's 1,000 gallon rating, hauler permit current, both signatures taken at the truck.

Step 9: 90 days times 25 divided by 29.2 is 77 days. Rounded down to the next interval the account can schedule, 60 days, because rounding on this one runs toward more frequent service and not less. Next service set at 60 days, with a note that the interval is reviewed again once the outlet tee is back in, since a unit that has been passing FOG downstream will accumulate differently once it stops.

References

• 29 CFR 1910.1000 Table Z-2 for the hydrogen sulfide ceiling, and 29 CFR 1910.146 for permit-required confined spaces, which is why nobody in this procedure enters an interceptor.
• Your municipal FOG ordinance for manifest content, hauler permitting and record retention, which are local requirements and vary between neighbouring jurisdictions.
• IPC Section 1003 for interceptor requirements as adopted by your authority having jurisdiction, in the edition it enforces.
• See related: the Plumbing grease interceptor sizing reference, which owns the 25 percent rule and the sizing methods, and the hydro jetting service standard for the kitchen branch.