If you run a restaurant kitchen, you already know grease is everywhere—on the flat top, in the fryer, coating every pan that comes out of the dish pit. What’s easy to forget is where it all goes after the rinse water disappears down the drain. That’s the job of your grease trap, and grease trap maintenance is one of those unglamorous back-of-house tasks that quietly determines whether your kitchen runs smoothly or grinds to a very expensive halt.
Neglect it, and you’re not just risking a slow drain. You’re risking a flooded kitchen floor during a Friday dinner rush, a surprise visit from a health inspector, or a fine from your local sewer authority. The good news: grease trap maintenance is entirely manageable once you understand how the system works and what to watch for.
Quick Answer
Grease trap maintenance means routinely removing accumulated fats, oils, and grease (FOG) so it doesn’t clog plumbing or violate local discharge limits. Most commercial kitchens need service every 1–3 months, though many municipalities—including the LOTT service area covering Olympia—require grease traps cleaned every 14 days and larger interceptors every 90 days.
What Is a Grease Trap and How Does It Work?
A grease trap (sometimes called a grease interceptor) is a plumbing device installed between your kitchen’s drains and the municipal sewer line. Its job is simple in concept: slow down wastewater long enough for fats, oils, and grease to separate out before the water continues downstream.
Here’s what happens inside one during normal operation:
- Warm, greasy wastewater flows in from sinks, dishwashers, and floor drains.
- Inside the trap, the water slows down and cools.
- Grease and oil, being lighter than water, rise and float to the top as a layer of scum.
- Solid food particles sink to the bottom as sludge.
- Relatively clean water exits from the middle layer, continuing on to the sewer system.
Smaller units, technically called hydromechanical grease interceptors, sit under the sink and hold a few gallons. Larger restaurants often use gravity grease interceptors buried outside the building, capable of holding hundreds of gallons. Either way, the trap only works as designed if the grease layer is removed before it builds up enough to escape into the outgoing water—which is exactly what routine grease trap maintenance is for.
Why Do Restaurants Need a Grease Trap?
Almost every commercial kitchen is required to have one, and the reasons go well beyond satisfying an inspector’s checklist.
Protecting Your Plumbing and Sewer Lines
FOG that isn’t captured travels down the pipe, cools, and hardens into a waxy buildup on pipe walls. Over time, that buildup narrows the pipe until wastewater can’t pass through it. According to the EPA, grease from restaurants, homes, and industrial sources is the single most common cause of reported sewer blockages, responsible for roughly 47% of them nationwide. A single restaurant can generate anywhere from 800 to 17,000 pounds of grease waste a year, so the cumulative effect on plumbing adds up fast without a trap doing its job.
Staying Compliant With Local Regulations
Most municipalities set numeric limits on how much FOG can legally be discharged into the sewer system—commonly around 100 mg/L, though local limits range from 50 to 450 mg/L depending on the jurisdiction. In the South Sound, the LOTT Clean Water Alliance—the regional utility serving Olympia, Lacey, and Tumwater—caps FOG discharge at 300 mg/L and requires food service establishments to keep documented maintenance records on-site for at least three years. Many cities and counties run their own dedicated FOG compliance programs for food service establishments, with routine inspections and reporting requirements—Union Sanitary District’s restaurant program is a good example of what one of these programs actually looks like in practice. Violations aren’t hypothetical: New York City, for example, has imposed fines of $1,000 per day for FOG discharge violations, and many utilities add ongoing surcharges of $100 to $700 or more to the sewer bills of non-compliant restaurants. If you’re not sure what your local requirement actually is, a quick call to a local grease trap service provider can usually get you an answer faster than digging through municipal code.
Protecting the Environment and Your Reputation
Grease that escapes into the sewer system doesn’t just disappear—it can contribute to sanitary sewer overflows, which release untreated wastewater into streets, waterways, and storm drains. For a restaurant, being named in a sewer overflow incident tied to your kitchen is the kind of local news story no amount of marketing can undo.
How Often Should a Grease Trap Be Cleaned?
There’s no single number that fits every kitchen, but there is a reliable rule of thumb the plumbing industry has used for decades.
The 25% Rule
The Plumbing & Drainage Institute’s PDI-G101 standard—the technical basis most grease interceptor sizing and service schedules are built on—holds that a grease trap should be pumped once the combined layer of grease and solids reaches 25% of the trap’s total liquid depth. Let it go past that point, and the trap loses the retention capacity it needs to actually separate grease from water, meaning FOG starts passing straight through into the sewer line.
In practice, that usually translates to a schedule like this:
| Kitchen Type | Typical Service Frequency |
| Small cafe or coffee shop | Every 2–3 months |
| Full-service restaurant | Every 4–8 weeks |
| High-volume kitchen (fryers, high meat/dairy use) | Every 2–4 weeks |
| Ghost kitchen/commissary with multiple tenants | Every 2–4 weeks |
*Actual frequency depends on trap size, menu, covers per week, and local ordinance requirements—use this table as a starting point, not a substitute for measuring your own trap.
Some health departments and sewer authorities set a mandatory minimum service interval regardless of how full the trap looks. In the Olympia area, for example, LOTT requires hydromechanical interceptors—the smaller, under-sink units most restaurants use—to be pumped at least every 14 calendar days, and larger gravity interceptors at least every 90 days, regardless of the 25% threshold. It’s worth confirming your specific local requirement rather than relying on the general rule alone.
How Do You Know When a Grease Trap Needs to Be Cleaned?
Between scheduled services, a few warning signs tell you the trap needs attention sooner:
- Slow-draining sinks or floor drains, especially near the dish pit or prep sinks
- Gurgling sounds coming from drains as water struggles to pass
- A persistent sour or rotten odor near drains or the trap access lid, even after cleaning
- Grease visibly pooling at floor drains or backing up into sink basins
- A noticeably thick layer visible when you open the trap’s inspection lid
- Fruit flies or drain flies congregating near floor drains
If you notice more than one of these at once, don’t wait for your next scheduled service—call for a cleaning before it turns into a shutdown. Odor in particular tends to have a few distinct root causes worth understanding on their own.
What Happens If You Don’t Clean a Grease Trap Regularly?
Skipping grease trap maintenance rarely causes a problem right away, which is exactly what makes it easy to deprioritize. The consequences tend to show up all at once, and usually at the worst possible time.
Costly Repairs and Downtime
A fully blocked line can back up into your kitchen mid-service, forcing you to close, evacuate the space for cleanup, and call an emergency plumber at after-hours rates. If grease has already worked its way past the trap and into your building’s plumbing, that stops being routine maintenance and becomes a plumbing repair job—a more expensive problem than the pump-out that would have prevented it.
Fines, Surcharges, and Compliance Violations
An overflowing or non-compliant trap can trigger fines from your local sewer authority, ongoing surcharges added to your utility bill, or a failed inspection that puts your operating permit at risk.
Health Inspections and Reputation Risk
Grease odors and pest activity near a neglected trap are exactly the kind of thing a health inspector notices—and exactly the kind of thing a customer notices if it drifts into the dining room. A failed health inspection is public record in most jurisdictions, and it’s not the kind of publicity a restaurant recovers from quickly.
What Does Grease Trap Maintenance Cost?
Routine maintenance is almost always cheaper than the alternative. Here’s a general sense of what restaurants typically budget for, based on trap size and service type:
| Service | Typical Cost Range* |
| Routine under-sink trap pumping | 150–300 |
| Routine in-ground interceptor pumping | 300–600 |
| Emergency pumping (overdue/backed up) | 500–1,200+ |
| Line jetting/cleanout after a blockage | 300–900 |
| New grease trap installation | 500–3,000+ |
*Costs are estimates only and will vary based on trap size, your local service provider, and regional labor rates.
Building a Grease Trap Maintenance Routine
Consistent habits between professional services go a long way toward keeping your trap—and your kitchen—running clean.
- Scrape plates and pans before washing. Send food scraps to the trash or compost, not the sink.
- Use sink strainers on every drain to catch solids before they reach the trap.
- Never pour used cooking oil down the drain. Collect it in a dedicated container for pickup or recycling.
- Log every service date and keep receipts—LOTT, for example, requires food service establishments to keep three years of maintenance records on-site, and many other jurisdictions have similar requirements.
- Train kitchen staff on what can and can’t go down the drain; turnover means this needs repeating regularly, not just once.
- Schedule inspections between pump-outs so you’re never guessing how full the trap is.
A written schedule posted in the kitchen, similar to a cleaning checklist, keeps this from becoming the task everyone assumes someone else is handling. If you’d rather have a professional set that schedule for you, Goebel’s grease trap team can build one around your kitchen’s actual volume.
Prioritize Grease Trap Maintenance
Grease trap maintenance isn’t the most exciting line item in a restaurant’s operating budget, but it’s one of the few that quietly protects everything else—your plumbing, your health inspection score, your compliance standing, and your ability to open on time every single day. A trap that’s serviced on a predictable schedule almost never makes the news. One that isn’t, eventually does.
If your kitchen doesn’t have a documented service schedule yet, that’s the first thing worth fixing—and it’s a lot easier to fix than most operators expect.
About Goebel
Goebel is a family-owned and locally operated septic and portable sanitation services company that has been serving homeowners, event organizers, and local businesses since 1979. Alongside routine septic pumping and inspections and porta potty rentals for events, Goebel provides grease trap pumping services for restaurants and commercial kitchens throughout the Olympia and South Sound area—handling everything from small under-sink units to large in-ground interceptors. Fast, friendly, and fair, the Goebel team brings 40+ years of hands-on experience to every job. Have a grease trap that needs service, or want help setting up a maintenance schedule that keeps you compliant? Contact Goebel to schedule service or ask a question today.