For most restaurants in Tigard, Beaverton, and Hillsboro, grease trap maintenance means pumping the trap every 30 to 90 days and never letting fats, oils, grease, and solids build past 25% of the trap's liquid depth. Interior "under-sink" traps in busy kitchens often need service every two to four weeks, while larger exterior interceptors can go a quarter between pump-outs. You also need to keep written service records on site, because Clean Water Services and health inspectors will ask for them.
Why Grease Traps Fail in Washington County Kitchens
We've serviced grease interceptors for pizza kitchens on Pacific Highway, sushi restaurants in Lake Oswego, brewpubs in Sherwood, and cafeteria kitchens in Hillsboro office parks. The failure pattern is almost always the same: nobody knows how full the trap actually is until something backs up during a Friday dinner rush.
A grease trap works by slowing wastewater down enough for grease to float and solids to sink, letting relatively clean water pass out the middle. That only works when there is room in the tank. Once the grease cap and the solids layer together take up more than a quarter of the depth, the water flowing through has nowhere to sit still, and FOG rides straight out into your building drain.
Oregon's cool ground temperatures make this worse than in warmer climates. In our experience, grease that escapes a trap here congeals within 15 to 30 feet of the building, usually in the first horizontal run of the lateral. We've pulled two-inch-thick grease rinds out of 4-inch lines under parking lots in Tualatin that had never been jetted in a decade.
How to Size Your Pumping Schedule
Forget generic calendars and measure your own trap. Use a clear dipstick or a coring tube, drop it through the access port, and note two things: the thickness of the floating grease cap and the depth of the solids on the bottom. Add them together and compare to the total liquid depth.
Here's what we typically see across our commercial accounts:
25 to 50 gallon under-sink traps in a high-volume kitchen with a fryer program: every 2 to 4 weeks. These fill fast and they are the ones we most often find completely solid.
Small exterior interceptors (500 to 750 gallons) at a single-location restaurant: every 60 to 90 days is common, though a busy burger or breakfast spot can hit the 25% line in 45.
1,000 to 1,500 gallon interceptors serving multi-tenant food courts or a full-service kitchen: usually quarterly, sometimes twice a year for lower-volume concepts like a coffee shop with light food prep.
Once you've measured for two or three cycles, you'll know your real interval. Lock it into a recurring service agreement so it happens whether or not your kitchen manager remembers.
Daily Kitchen Habits That Cut Your Costs
Pumping is the expensive part, so stretch the interval with better upstream practices. Dry-wipe pans and plates before they hit the dish sink. Install and actually use solids strainers on every compartment of the three-compartment sink. Collect fryer oil in a rendering bin rather than pouring it down a drain, even diluted.
The biggest one we push on our restaurant clients: stop using hot water and degreasing detergent to "flush" grease down the line. Those emulsify the grease so it passes right through the trap, then it cools and re-solidifies in the sewer lateral where nothing can catch it. A trap that looks clean while the lateral is plugging is the worst of both worlds.
Also be skeptical of enzyme and bacterial drain additives sold as a substitute for pumping. They can help with odor and minor buildup, but they don't remove solids, and many sanitary districts specifically prohibit products marketed as grease dispersants.
Compliance, Records, and Local Requirements
Restaurants in the Portland metro discharging to Clean Water Services are considered food service establishments subject to FOG rules. That means an approved interceptor sized for your fixture load, maintenance at intervals that keep you under the 25% threshold, and records available for inspection. Keep three years of manifests in a binder or a shared folder near the manager's desk. We've watched operators get written up not for a dirty trap, but for having no paperwork to prove they'd ever serviced it.
If you're remodeling, adding a fryer line, or taking over an existing space, have the interceptor sizing verified before you open. We regularly inspect traps in second-generation restaurant spaces in Beaverton and Tigard that were sized for the previous tenant's much smaller menu. Our commercial plumbing team can camera the lateral, confirm trap capacity, and document what you've got before the health inspector does.
When You Need More Than a Pump-Out
If backups continue right after a fresh pumping, the trap isn't the problem anymore — the downstream line is. That calls for a camera inspection and usually hydro jetting to cut hardened FOG off the pipe walls. We've restored 4-inch laterals from about 30% flow capacity back to full bore in a single jetting visit. Once the line is clean, a quarterly jetting schedule paired with correct pumping keeps most kitchens out of trouble indefinitely.
Ready to get your grease trap on a real schedule instead of a guess? Call Hydro Plumbing at (971) 241-2628 for grease trap inspection, hydro jetting, and commercial maintenance agreements throughout Washington & Yamhill Counties — including Tigard, Beaverton, Hillsboro, Lake Oswego, Tualatin, and Sherwood. CCB #254405.