Drain backing up?
Five questions, one plain-English answer about what's wrong.
Slow sinks, standing water, and sewage smells all look alike, but they trace to five different failures inside a commercial kitchen drain system. Answer five quick questions about what you're seeing and we'll tell you whether it's the grease trap, a blocked line, a venting issue, or something else, plus the right service to book. No diagnostic fee, no contractor visit required to find out.
Slow drains and sewage smells look the same. They're not
Most restaurant operators call it a "drain problem" and leave it at that. But there are five distinct things that can go wrong in a commercial kitchen drain system, and they require five different fixes. Booking the wrong service wastes money, delays the real repair, and in the worst cases makes the underlying problem harder to fix.
The most common mistake: pumping the grease trap when the drain line is blocked. The pump-out clears nothing, the drain stays slow, and the operator assumes the service didn't work. The real problem was never the trap.
Here's what's actually happening under your kitchen floor.
What a grease trap actually does
Every commercial kitchen drain runs through a grease trap before reaching the city sewer. The trap is a passive interceptor: a sealed box, either under the sink or buried in-ground, that holds wastewater long enough for fats, oils, and grease (FOG) to float to the top and food solids to sink to the bottom. Clean water exits through the middle outlet and continues to the sewer.
The trap has a finite capacity. As FOG accumulates, the usable space shrinks. When the trap reaches roughly 25% solid and grease buildup, the local health-code threshold, it can no longer separate effectively. FOG bypasses into the city sewer line, backing up into your kitchen and triggering health code violations.
The drain lines are separate from the trap. They carry wastewater from your sinks and floor drains to the trap inlet. These lines accumulate their own FOG buildup, food debris, and mineral scale over time, entirely independent of whether the trap itself is full. A blocked drain line produces the exact same symptoms as a full grease trap: slow drainage, standing water, foul odor. The only way to tell them apart is to know which part of the system is failing.
Five things that go wrong. Five different fixes
How often should a restaurant pump its grease trap?
The short answer: more often than most operators think.
Southern California regulations require grease traps to be pumped before they reach 25% capacity, meaning the combined depth of floating grease and settled solids equals one quarter of the trap's total volume. For most commercial kitchens, that threshold arrives every 30 to 90 days depending on the volume of food prepared and the proportion of fried or fatty items on the menu.
A high-volume burger or fried chicken operation may need monthly pump-outs. A café with light kitchen activity may be able to extend to 90 days. The only way to know your kitchen's actual interval is to track when the trap hits 25% across two or three service cycles.
What happens when you go overdue: FOG begins bypassing into the outlet pipe and accumulating in the line between the trap and the city sewer. That line is harder and more expensive to clear than the trap itself. Operators who let pump intervals lapse consistently tend to face hydro jetting bills they could have avoided entirely.
Boh documents every pump-out with a service manifest compatible with Southern California health inspections. If an inspector asks for your grease trap service records, you have them.
Grease trap violations are among the most common health inspection failures in Southern California
Southern California health inspectors check for evidence of grease trap maintenance on routine inspections. A trap at or beyond 25% capacity is a citable violation. An uninspected or undocumented trap, one with no service records, is a red flag that invites closer scrutiny of everything else in the kitchen.
The documentation requirement is specific: inspectors want to see dated service manifests showing who performed the pump-out, the volume removed, and the disposal facility used. A receipt from a vendor is not sufficient. A proper manifest is.
Every Boh grease trap service produces a compliant manifest, delivered digitally, stored in your service history. You do not have to chase paperwork.
Common questions
What is the difference between grease trap pumping and hydro jetting?
Grease trap pumping removes the accumulated FOG and solids from inside the trap itself: the box. Hydro jetting clears the drain lines: the pipes leading to and from the trap. They address different parts of the system. A full trap needs pumping. A blocked pipe needs jetting. If both are present, the trap is pumped first.
My grease trap was just cleaned but the drains are still slow. Why?
A recently pumped trap rules out trap saturation as the cause. Persistent slow drainage after a pump-out almost always indicates a blocked drain line: the restriction is in the pipe, not the trap. Hydro jetting the lines is the next step.
How do I know if my grease trap is full?
The clearest signs are multiple drains backing up simultaneously, a sewage smell that is noticeable away from the sink, and slow drainage across the kitchen rather than at one fixture. A single slow sink is more likely a line restriction than a full trap. The only way to confirm is to open the trap and measure the FOG layer, something your service technician does at every pump-out.
Can a grease trap issue cause a health inspection failure?
Yes. A trap at 25% capacity or above is a direct violation under Southern California health regulations. An uninspected trap, or one with no documentation of recent service, can also result in a citation. Inspectors are trained to look for evidence of active grease management. A clean trap with current paperwork closes that line of inquiry immediately.
What happens if the grease trap overflows into the city sewer?
Grease in the city sewer system is a municipal violation. FOG that bypasses the trap accumulates in the sewer line, causing blockages that affect neighboring properties. Restaurants found responsible for sewer blockages face fines from the city separate from any health department citation. It is significantly more expensive to respond to a sewer complaint than to maintain a regular pump schedule.
What is hydro jetting and when is it necessary?
Hydro jetting uses high-pressure water, typically 3,000 to 4,000 PSI, to scour the interior walls of drain pipes. It removes FOG buildup, food debris, mineral scale, and any other accumulation that has reduced pipe diameter. It is necessary when mechanical snaking has failed to restore flow, when a line has gone unmaintained for an extended period, or when recurring blockages suggest buildup rather than a one-off clog.
Do I need a special permit to have my grease trap pumped?
The pump-out itself does not require a permit. The waste removed from a grease trap is classified as a non-hazardous waste stream and must be transported and disposed of by a licensed waste hauler. The manifest documenting this disposal chain is what Southern California inspectors look for, not a permit. Boh uses licensed haulers on every job and provides the manifest automatically.