Grease Trap Pumping Calculator
Estimate how often your grease trap needs cleaning based on your kitchen's specifics.
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How to Calculate Your Grease Trap Pumping Schedule
This free grease trap pumping calculator helps restaurant owners in California determine how often their grease trap needs cleaning. Enter your trap size in gallons, select your restaurant type, provide your average daily covers, and choose your deep fryer count. The calculator estimates a recommended pumping frequency in weeks and flags whether your current schedule puts you at risk for FOG violations.
The calculation is based on the 25% rule used by most California health departments and regional water boards. When fats, oils, and grease exceed 25% of your trap capacity, you are in violation and risk fines ranging from $200 to $5,000 per incident depending on your jurisdiction. High-volume frying operations with multiple fryers need significantly more frequent pumping than bakeries or cafes with minimal grease output.
What Size Grease Trap Does My Restaurant Need?
Grease trap sizing depends on your kitchen flow rate and local plumbing codes. Most under-sink units range from 20 to 50 gallons and serve small cafes, food trucks, and bakeries. Full-service restaurants typically need 50 to 100-gallon traps. High-volume operations like fast food chains, fried chicken restaurants, and hotel kitchens often require 150 to 200-gallon in-ground interceptors. If you are unsure about your trap size, check the nameplate on the unit or ask your plumber during the next service visit.
How Often Should a Restaurant Pump Its Grease Trap in California?
California does not mandate a single universal pumping frequency, it depends on your trap size, kitchen volume, and what you cook. However, most municipal FOG programs require that you pump before the grease cap exceeds 25% of total trap depth. As a general guideline, small indoor traps need pumping every 30 to 60 days, mid-size restaurant traps every 60 to 90 days, and large outdoor interceptors monthly. Fast food and heavy frying operations should err on the shorter end of that range.
What Happens If You Skip Grease Trap Cleaning?
Skipping scheduled grease trap maintenance creates a cascade of problems. Grease backs up into your kitchen sinks and floor drains, producing foul odors that reach your dining room. FOG entering the municipal sewer system triggers violations from your local water authority. Health inspectors can issue citations, mandatory increased pumping schedules at your expense, or in severe cases shut down food preparation until the issue is resolved. Emergency grease trap service costs two to five times more than scheduled cleaning.
Methodology, sources, and limits
Read this before you act on the number above. This calculator produces a planning estimate for budgeting and scheduling. It does not determine compliance, and it does not replace the requirement your local agency has already set for you.
What it uses
Four inputs: your grease trap capacity in gallons, your restaurant type, your average daily covers, and your deep fryer count. Nothing is measured, looked up, or stored.
The formula
Weeks between cleanings equals trap gallons divided by daily covers times a restaurant type multiplier times a fryer factor. The result is rounded and clamped to a floor of 2 weeks and a ceiling of 12 weeks. Cleanings per year is 52 divided by that interval, rounded up. The type multipliers are fast food 1.5, pizza 1.3, cafeteria 1.2, full service 1.0, other 1.0, and bakery 0.5. The fryer factors run from 0.5 with no fryers up to 2.0 at five or more.
Those multipliers are our own weighting, drawn from what we see across kitchens. They are not published values and no agency endorses them. Two restaurants with identical inputs can fill a trap at very different rates depending on menu, scraping practice, dish machine temperature, and how much oil goes down the sink in the first place.
The rule that actually governs: the 25 percent rule
California FOG programs are run by local sanitation districts and cities, not by a single statewide pumping schedule, and the widely used standard across them is the 25 percent rule. The Orange County Sanitation District states it directly in its ordinance fact sheet: grease interceptors shall be fully pumped out and cleaned at a frequency such that the combined FOG and solids accumulation does not exceed 25 percent of the total design hydraulic depth of the grease interceptor. OC San calls this the 25 percent rule, and it layers a floor on top: every food service establishment with a grease interceptor maintains it not less than every 6 months, and quarterly by default until a frequency has been established from real data. The Castro Valley Sanitary District words it the same way, traps and interceptors cleaned as often as necessary and at a minimum every six months, with floating grease and settled solids never exceeding 25 percent of the hydraulic depth.
Note what that means in practice. The 25 percent rule is a condition, not a calendar. Only lifting the lid and measuring the grease and solids layer against the liquid depth tells you where you stand. This calculator estimates how often you will probably hit that point. It cannot tell you whether you are at it today.
Local requirements override this tool
Your sanitation district or municipal FOG program sets the requirement that binds you, and agencies differ on both the threshold and the minimum interval. They can also assign or change your maintenance frequency directly, and OC San reserves exactly that right in its ordinance. If your permit, your inspector, or your agency has given you a schedule, that schedule governs regardless of what this page says. Use this number to plan and to budget, then confirm it with your agency.
Known limitations
- It measures nothing. It has no idea what is in your trap right now.
- Daily covers is a crude proxy for grease load. A 200-cover salad and sandwich kitchen and a 200-cover fry house are not the same trap.
- Output is capped at 2 to 12 weeks. It will never return a shorter or longer interval even where one is warranted.
- The 20 to 200 gallon sizes here are grease traps and small units. Los Angeles County Public Works defines a grease trap as a small multi-baffle unit of about 25 to 75 gallons and a grease interceptor as a device of 750 gallons or greater, and large in-ground interceptors are sized and scheduled under separate rules, including the California Plumbing Code sizing tables.
- It says nothing about your used cooking oil paperwork. That is a separate regime: grease trap waste and used cooking oil both have to move with a transporter registered with CDFA under 3 CCR 1180.20.
- It is not legal advice and not a compliance determination.
Sources
- Orange County Sanitation District, Core Elements: Fats, Oils, and Grease (FOG) Ordinance No. OCSD-25 (PDF)
- Castro Valley Sanitary District, Fats, Oils, and Grease Control Program
- Los Angeles County Public Works, Pretreatment Guidelines for Restaurants and Food Service Operations (PDF)
- 3 CCR 1180.20, Transporters of Inedible Kitchen Grease
Last reviewed: July 30, 2026. Every source link above was checked on that date. Local FOG ordinances change, so confirm the current requirement with your own agency.
Grease trap pumping, frequently asked
Check the nameplate on your grease trap, it lists the capacity in gallons or GPM. Most under-sink traps are 20-50 gallons. In-ground interceptors are typically 100-200+ gallons. If you cannot find the nameplate, your plumber or grease hauler can measure it.
An overfull grease trap causes backups, foul odors, and grease entering the sewer system. This can trigger health department violations, city fines, and expensive emergency plumbing. The 25% rule says you should pump before fats, oils, and grease exceed 25% of the trap capacity.
Yes. A fast food restaurant with multiple fryers produces significantly more grease than a bakery or cafe. The type of cooking you do, deep frying, grilling, sauteing, directly affects how quickly your trap fills up.
In California, grease trap waste must be transported by a hauler registered with the CDFA as an Inedible Kitchen Grease transporter. Self-hauling is not legal for commercial quantities. A registered hauler also provides the manifests you need for health inspections.