If you run a kitchen in Portland, Tigard, Hillsboro, or Lake Oswego, your grease service schedule isn’t a “set it and forget it” item — it’s a maintenance rhythm that protects your plumbing, reduces odors, and helps you stay ready for inspections. If you manage multiple locations (Oregon City to McMinnville), a consistent schedule plus solid documentation is the difference between smooth operations and emergency calls.
Quick answer
A good starting point is to service your grease trap/interceptor on a recurring schedule, then adjust based on what actually builds up. In the City of Portland, minimum cleaning frequencies are spelled out in the City’s FOG (Fats, Oils, and Grease) administrative rules — and your schedule may need to be more frequent depending on volume and menu.
Grease trap vs grease interceptor (and why it changes frequency)
Hydromechanical grease interceptor (HGI):
Smaller units (often indoors). Because capacity is limited, they usually need more frequent cleaning.
Gravity grease interceptor (GGI):
Larger, typically outdoor/in-ground interceptors. These often follow longer service intervals — but high-volume kitchens can still fill them quickly.
Portland minimum cleaning frequency (City of Portland)
The City of Portland’s FOG administrative rules state grease interceptors must be cleaned no less frequently than:
- Every 30 days for an HGI
- Every 90 days for a GGI
Portland also requires maintenance reporting within 14 days after each cleaning, including details like cleaning date, estimated depth of FOG/solids prior to cleaning, any defects, and disposal information.
If you operate outside Portland (Tualatin, Sherwood, Banks, North Plains, McMinnville, etc.), requirements may differ by sewer agency — but having a defensible schedule and documentation is still the right move.
A practical scheduling tool: the “25% rule”
Even when calendar minimums exist, many pretreatment programs use a practical benchmark: service the unit when the combined FOG layer + settled solids reaches about 25% of the device’s liquid depth.
Plain English: don’t wait for smells or backups — schedule service before separation stops working.
Realistic starting schedules (rule-of-thumb)
Use this as a starting point, then tighten/loosen based on buildup:
- High-volume / heavy-grease menus (fried foods, high covers): start monthly (or more often if it fills quickly)
- Average full-service restaurants: start monthly to quarterly depending on device type and volume
- Low-grease / light prep / cafés: start quarterly, then adjust
If you’re in Portland: you still must meet the City’s minimum frequency for your device type.
What changes your schedule the fastest (5 big drivers)
- Covers / volume: more flow = faster accumulation
- Menu: fryers, greasy proteins, and oily sauces build FOG faster
- Device type & size: smaller devices fill faster
- Staff habits: scraping and dry-wiping dishes cuts FOG load dramatically
- Operational changes: staffing turnover, seasonal rushes, or menu changes can spike buildup
Warning signs you’re overdue
- Grease odors near sinks or floor drains
- Slow drains in multiple fixtures
- Gurgling during peak hours
- Repeat clogs that “mysteriously” come back
- Grease showing up downstream (cleanouts, floor drains)
- Staff saying “it’s been a while”
Hidden fees to ask about (before you approve service)
Even if the base price looks good, ask what gets added:
- Fuel surcharges
- Environmental / disposal fees
- Administrative / shop fees
- Access issues (locked lids, blocked covers, tight service windows)
These aren’t automatically wrong — they just need to be disclosed upfront so you can compare vendors fairly.
What documentation you should get after every service
At minimum, keep a log that includes:
- Date serviced
- Which unit was serviced (unit ID / location)
- Notes on condition (damage, missing tees/baffles, broken lids, etc.)
- Disposal documentation (where waste went)
- Photo evidence (when possible)
Service Area: West Side Drain serves Portland and surrounding communities including Hillsboro, Tigard, Lake Oswego, Oregon City, Tualatin, Sherwood, Banks, North Plains, and McMinnville.
Want fewer emergencies and cleaner documentation? West Side Drain can set up a recurring grease service schedule based on your kitchen volume and interceptor type. Reporting to the local FOG regulator is included with our service.
Call: (503) 522-2727
Email: info@westsidedrain.com
FAQs
How often should restaurants pump grease traps in Portland?
Portland’s FOG administrative rules state minimum cleaning frequencies of every 30 days for HGIs and every 90 days for GGIs (or more often if needed).
What is the “25% rule” for grease interceptors?
A common guideline is to service the device when the combined floating grease and settled solids reach about 25% of the unit’s liquid depth.
Can we just use additives/enzymes to “digest” grease instead of pumping?
Some agencies restrict additives used to break down grease for discharge to the sewer. If you operate in Portland, follow the City’s FOG program rules and requirements.
What records should restaurants keep after grease service?
Keep the service date, unit identification/location, notes on condition, and disposal documentation. In some jurisdictions (including Portland), reporting details and timelines can be specific.
