The short answer

If your restaurant is in Biloxi, Gulfport, D'Iberville, Long Beach, or Pass Christian, your grease trap falls under the Harrison County Utility Authority (HCUA) grease trap regulation. That regulation does not set one fixed interval for every kitchen. Instead it says two things that work together:

  • Clean as often as needed. Generators must clean and/or pump their traps "at whatever interval is necessary" so that what leaves the trap doesn't violate the sewer use ordinance (Article III, Section 2 and Article IV, Section 2).
  • Don't let 90 days pass. A generator that does not clean its trap during any 90-day period, and has not been granted an exception, can be ordered to have the trap inspected and tested (Article IV, Section 3). HCUA's grease generator checklist (dated 1/19/2022) puts it plainly: generators must have their traps cleaned at a minimum of every 90 days to stay in compliance.

So the practical rule for Harrison County kitchens is at least every 90 days, and sooner if your trap fills faster. Most busy kitchens fall into the "sooner" group.

What counts as "cleaned"

A pump-out only counts if it is a real cleaning. HCUA defines "clean" as removing the entire contents of the trap, scraping the walls or cleaning them with high-pressure water, and then pumping again. Skimming the grease cap off the top doesn't meet that definition. When you compare providers, ask whether their standard visit is a full pump-out with scraping. See what a full grease trap pumping should include.

The 25% rule: how to tell when your trap is really full

The 90-day mark is a ceiling, not a target. The most common way to decide whether a trap needs service sooner is the 25% rule: pump before floating grease plus settled solids take up about a quarter of the trap's liquid depth. Past that point the trap has less calm water to separate grease, and more of it slips through to the sewer.

It's worth knowing where that number comes from. HCUA's regulation does not set a percentage. The 25% figure is a widely used industry guideline, and one local rule writes it down: the Hancock County Utility Authority's 2011 Fats, Oils, and Grease Ordinance requires more frequent pumping when 25% or more of the wetted height of a grease trap or interceptor, measured from the bottom of the device to the invert of the outlet pipe, holds floating material, sediment, oils, or grease.

If you're outside Harrison County

  • Bay St. Louis and Hancock County: the Hancock County Utility Authority's FOG ordinance sets a stricter baseline. Interceptors must be completely evacuated at least every 30 days, or more often when the 25% trigger is hit, discharge limits are exceeded, or there's a history of non-compliance. Owners can request a longer interval in writing, but every interceptor must be fully evacuated, cleaned, and inspected at least once every 90 days. See grease trap cleaning in Bay St. Louis.
  • Ocean Springs, Pascagoula, and Jackson County: wastewater here is treated by the Jackson County Utility Authority (JCUA). JCUA's Rules and Regulations (revised March 9, 2026) place food service businesses that are JCUA retail customers in "Category 2FS," with a discharge contract, an oil and grease limit of 150 mg/L, and monthly effluent sampling, but we did not find a fixed pumping interval in that document. Cities that collect their own sewage can have their own ordinances, so check with your city as well. See Ocean Springs and Pascagoula.

How to set the right schedule for your kitchen

The U.S. EPA notes that the right maintenance frequency for grease traps and interceptors "depends greatly" on how much FOG a facility generates and on the best management practices it follows. In practice, these are the things that move your interval:

  • Trap size. A small under-sink or in-floor trap holds far less than an outdoor interceptor and can fill in days at a busy kitchen. Not sure what you have? See grease trap vs. grease interceptor.
  • Menu. Fryers, seafood boils, gravies, and anything heavy on butter or meat fat load a trap faster than a salad-and-sandwich menu.
  • Volume and season. Coast kitchens can be quiet one month and packed the next. A schedule that works in January may be too long for a holiday weekend or a big event week.
  • Kitchen habits. Scraping plates into the trash, collecting fryer oil for recycling, and keeping food solids out of drains all stretch the time between pump-outs. The EPA notes that kitchens using these practices can often reduce how often their devices need service.

A simple way to dial it in:

  1. Start with a conservative interval, well inside 90 days (or 30 days for an interceptor in Hancock County).
  2. Ask your provider to measure and record grease and solids depth at every visit.
  3. If the trap is consistently near 25% at pump-out, keep the interval or shorten it. If it's consistently well under, ask whether it can be extended, without ever passing your local maximum.
  4. Keep every manifest. In HCUA's area, you or your agent sign the HCUA Grease Trap Waste Manifest before each load leaves, and those records show your schedule is being followed.

Can you get permission to pump less often?

In Harrison County, possibly, but only with approval. HCUA's regulation allows less frequent cleaning only if the Director determines you'll still comply with sewer use rules; you apply to the Director for an exception and provide whatever documentation is required (Article III, Section 5). The Director can also require more frequent cleaning (Article III, Section 4). Until you have an approved exception, plan on the 90-day maximum. For the full rulebook, read our HCUA grease trap requirements guide, and if a pump-out is overdue, see the signs your trap needs pumping now.