Opening a restaurant in Maryland this summer? Learn grease trap sizing, permits, cost, installation, and the 25% cleaning rule before you open.
Grease Trap Installation for New Maryland Restaurants
If you are opening a restaurant, cafe, or commercial kitchen in Maryland this summer, a grease trap is one of the first pieces of equipment you need to plan for, not one of the last.
In Anne Arundel County and the surrounding areas we serve, a food service business generally cannot begin discharging kitchen wastewater into the county sewer system until an approved grease interceptor is installed and permitted.
Getting this step right before your opening date protects your plumbing, keeps you on schedule with inspections, and helps you avoid fines once you are serving customers.
This guide walks new restaurant owners through:
- What a grease trap does
- How sizing and permits work in Maryland
- What installation involves
- How to plan maintenance from day one
What a Grease Trap Does and Why Your Restaurant Needs One
A grease trap, also called a grease interceptor, is a device that captures fats, oils, and grease (often shortened to FOG) from kitchen wastewater before that water flows into the sewer system.
Grease is lighter than water and does not mix with it, so inside the trap the grease and oils rise to the top while heavier solids settle to the bottom.
A system of baffles holds these materials back so that relatively clear water can pass through and continue on to the sewer.
FOG is a leading cause of sewer blockages and backups
When grease is allowed into sewer lines, it cools, hardens, and builds up until it restricts or blocks flow, which can cause overflows inside your kitchen or in the public system.
That is why counties and water authorities require food service establishments to install grease traps and keep them maintained.
Do You Legally Have to Have a Grease Trap in Maryland?
In most cases, yes. Maryland grease trap requirements are set at the county and water-authority level, and the food service industry is specifically regulated.
Under Anne Arundel County Code, any establishment that puts wastewater containing FOG into the county sewer system is required to install at minimum a 500 gallon grease interceptor, located outside the building it serves and accessible for servicing.
New food service facilities are expected to comply before they begin discharging.
Sizing: Choosing the Right Grease Trap for a New Kitchen
Sizing is where many new restaurants make expensive mistakes.
- A trap that is too small fills quickly, needs frequent pumping, and lets grease escape into your lines.
- A trap that is much larger than needed adds cost and can create its own problems.
The right size depends on your kitchen, not on a rule of thumb.
Common factors that affect grease trap sizing include:
- The fixtures that drain into the trap, such as three-compartment sinks, pre-rinse sinks, dishwashers, mop sinks, and floor drains.
- The flow rate and volume of wastewater your kitchen produces during peak service.
- Your menu and cooking style, since heavy frying and grilling produce more grease than a low-oil concept.
- Seating capacity and the number of meals served, which some jurisdictions use in their calculations.
- Local code minimums, which can require a larger unit than a formula alone would suggest.
Is Plastic or Metal Better for Grease Traps?
There is no single best material.
The right choice depends on where the trap is installed, how much grease your kitchen produces, and your budget.
Each material has trade-offs.
Stainless steel
Stainless steel is durable, resistant to corrosion and high temperatures, and easy to keep sanitary, which makes it a common choice for smaller indoor, under-sink, or point-of-use units. It usually costs more up front than plastic.
Plastic (HDPE, polypropylene, or PVC)
Plastic units are lightweight, corrosion resistant, and often less expensive, which makes them popular for smaller operations and moderate grease loads.
Plastic resists rust, though it can be more vulnerable to impact damage and to very high temperatures than steel.
Concrete or large in-ground interceptors
Large outdoor interceptors that serve an entire kitchen are frequently in-ground tanks.
In many Maryland jurisdictions, including Anne Arundel County, the primary interceptor must be located outside the building and accessible for pump-truck service.
For that reason, the outdoor unit type is often driven by code and site conditions rather than personal preference.
Because material choice interacts with placement, code, and sizing, decide it together with your plumber and your local authority rather than in isolation.
Who Installs a Grease Trap?
Can You Install Your Own?
For a commercial kitchen, grease trap installation is not a do-it-yourself project.
It typically involves:
- Selecting an approved unit
- Obtaining permits
- Meeting plumbing code
And in many cases:
- Excavation
- Concrete work
- Underground piping
Most jurisdictions require this work to be performed by a licensed plumber who understands local code, and some require engineered drawings and pre-installation approval before work begins.
Expert septic pumping and cleaning Importance
So while a homeowner might install a very small passive trap in some settings, a restaurant grease interceptor is a permitted, code-governed installation.
Plumbers do install grease traps, and using a licensed professional is usually a code requirement rather than just a recommendation.
Annapolis Septic Service covers:
- Grease trap maintenance
- Pumping
- Cleaning
- Inspection
How Grease Trap Installation Usually Works
Every project is different, but a typical path for a new restaurant looks roughly like this.
Treat this as a general overview, not a fixed procedure, since your county and site conditions will shape the details.
Confirm requirements with your local authority
Contact your county Department of Public Works or water authority’s FOG or pretreatment program to learn sizing rules, permit steps, and whether a discharge permit is required.
Have a licensed plumber or design professional review your kitchen
They assess which fixtures drain to the trap, calculate the size, and choose an approved unit and location.
Submit plans and obtain permits
Many jurisdictions require plan review and approval before installation begins, sometimes alongside your building permit and health department review.
Install the unit and connect the plumbing
For an outdoor interceptor this often includes excavation, setting the tank, piping, venting, and accessible covers at grade.
Pass inspection
The authority inspects the installation before you begin discharging wastewater.
Set up your maintenance and recordkeeping plan
Once the trap is in service, regular pumping, cleaning, and documentation keep you compliant.
How Much Does It Cost to Install a Grease Trap?
Cost varies widely based on the size and type of trap, your site conditions, and local code requirements, so there is no single price.
To give you a sense of scale using published 2026 market estimates:
- A small point-of-use under-sink trap and its installation often falls in the low hundreds to around a thousand dollars
- A larger in-ground interceptor for a full-service restaurant can run several thousand dollars or more once excavation, piping, and concrete work are included
Factors that influence your installation cost include:
- Trap or interceptor size and type.
- Indoor point-of-use unit versus outdoor in-ground interceptor.
- Excavation, concrete, and underground piping needs.
- Site access and existing plumbing layout.
- Permit and plan-review requirements in your jurisdiction.
Call 410-224-2461 or request grease trap free quote to get started. Ask about available veteran discounts.
Plan Maintenance Before You Open: The 25% Rule
A grease trap only works when it is maintained.
The widely used industry guideline is the 25% rule: a trap should be pumped and cleaned before the combined layer of floating grease and settled solids reaches 25% of the trap’s total capacity.
Past that point, the trap can no longer separate grease effectively, and FOG starts escaping into your lines and the sewer.
How often that threshold is reached depends on your kitchen.
For many restaurants, a trap reaches the 25% point somewhere in the range of one to three months of normal operation, and higher-volume kitchens may need more frequent service.
Some jurisdictions also set a fixed schedule, such as cleaning on a set cadence regardless of fill level, so your local rules may require service more often than fill rate alone would suggest.
A practical maintenance plan for a new restaurant usually includes:
- Scheduled pumping and cleaning based on your actual fill rate and your local minimum, whichever is more frequent.
- Keeping service records, often for three years, to show inspectors on request.
- Simple daily habits such as scraping and dry-wiping dishes before washing and keeping FOG out of drains.
- Watching for early warning signs like slow drains, odors, or visible grease, which suggest the trap is overdue.
Where Does the Water Go After a Grease Trap?
After wastewater passes through the trap, the grease and solids stay behind while the relatively clear water exits through the outlet pipe.
From there it continues to a larger interceptor if one is present, and then into the sanitary sewer system, or to an approved on-site system where applicable.
The captured grease and solids are pumped out during service and hauled away for proper disposal; they should never be reintroduced into a drain, sewer, or any body of water.
Set Up Your Grease Trap Maintenance Plan with Annapolis Septic Service
Opening a restaurant this summer means a lot of moving parts.
Once your grease trap is installed and permitted, a reliable pumping and cleaning schedule keeps it working and keeps you compliant.
As a family-operated Maryland septic company serving Annapolis and surrounding communities since 1967, Annapolis Septic Service can help you plan grease trap service for your new kitchen.
Call 410-224-2461 or request grease trap service to get started. Ask about available veteran discounts.
Frequently Asked Questions about Grease Trap Installation for New Restaurants Opening Duroing Summer
Can I install my own grease trap?
For a commercial kitchen, generally no. Restaurant grease trap installation is a permitted, code-governed project that usually requires a licensed plumber and, in many jurisdictions, plan review and inspection before you can discharge wastewater. A homeowner might install a very small passive unit in limited situations, but a restaurant interceptor should be installed by a licensed professional who knows your local code. Confirm the exact rules with your local authority and a licensed plumber.
How much does it cost to install a grease trap?
It depends on the size and type of unit, your site conditions, and local code. Using published 2026 industry estimates, a small under-sink trap and installation often runs from the low hundreds to around a thousand dollars, while a larger in-ground interceptor for a full-service restaurant can run several thousand dollars or more once excavation, piping, and concrete are included. For an exact price, get quotes from licensed plumbing contractors. Annapolis Septic Service does not set installation pricing.
Do plumbers install grease traps?
Yes. Grease trap installation is plumbing work, and most jurisdictions require it to be done by a licensed plumber who understands local code. For outdoor interceptors, installation can also involve excavation and concrete work. Annapolis Septic Service focuses on grease trap maintenance, including pumping, cleaning, and inspection, rather than acting as your installing contractor.
What is the 25% rule for grease traps?
The 25% rule is the common industry guideline for when to clean a grease trap. It means the trap should be pumped and cleaned before the combined layer of floating grease and settled solids reaches 25% of the trap’s total capacity. Once that layer passes 25%, the trap can no longer separate grease effectively, and FOG begins escaping into your plumbing and the sewer. For many restaurants this point is reached within one to three months, though local rules may require service on a set schedule.
Do you legally have to have a grease trap?
In most cases, food service establishments are legally required to have one. In Anne Arundel County, any business that discharges FOG-laden wastewater into the county sewer must install at minimum a 500 gallon grease interceptor located outside the building. Requirements vary by jurisdiction and water authority, so confirm the current rules with your county Department of Public Works or water authority before you build or open.
Is plastic or metal better for grease traps?
Neither is universally better; it depends on placement, grease load, and budget. Stainless steel is durable, sanitary, and common for smaller indoor units but costs more. Plastic is lightweight, corrosion resistant, and often cheaper but can be more vulnerable to impact and high heat. Large outdoor interceptors are frequently in-ground units, and in many Maryland jurisdictions the primary interceptor must be outdoors and accessible, which can drive the choice. Decide with your plumber and local authority.
Where does water go after a grease trap?
After the trap separates out grease and solids, the clearer water leaves through the outlet pipe and continues to a larger interceptor if present, then into the sanitary sewer system, or to an approved on-site system where applicable. The trapped grease and solids are pumped out during cleaning and hauled away for proper disposal, and they should never be put back into a drain, sewer, or waterway.
How many months before cleaning a grease trap?
For many restaurants, a grease trap needs cleaning somewhere in the range of every one to three months, but the right interval depends on your kitchen’s volume and your local rules. The guiding principle is the 25% rule: clean before grease and solids reach 25% of capacity. High-volume kitchens may need monthly service, while some jurisdictions require cleaning on a fixed schedule regardless of fill level. Track your actual fill rate and follow whichever is more frequent.