Grease Traps get expensive
Every restaurant owner budgets for the kitchen equipment. Almost nobody budgets correctly for the tank that sits under the floor and handles what comes off that equipment.
What is a grease trap?
A grease trap, or grease interceptor, is a plumbing device that catches fats, oils, and grease from kitchen wastewater before it reaches the city sewer. It works by slowing the flow so grease separates and floats while cleaner water passes through. Every municipality requires one for food service, sizes it based on your kitchen's output, and requires it to be pumped and serviced on a schedule.
It is one of the largest hidden costs in a restaurant buildout, because larger units have to sit below the floor.
The short version
Washing creates the requirement, not cooking.
There are two types of unit, and one of them may require cutting your slab.
Sizing is arithmetic based on your service type.
Under sizing it turns a one time construction cost into a permanent operating cost.
Ask the landlord in writing what already exists before you sign.
Washing creates the requirement, not cooking
This is the part that surprises people. It is not the fryer. It is the dishwasher, the three compartment sink, the pot sink, and all the rinsing of pans, plates, and flatware that sends fats, oils, and grease down the drain.
A good breakdown of how interceptors get sized and where people get it wrong is worth twenty minutes of any operator's time.
There are two kinds of unit, and the difference is a slab
Hydromechanical interceptors use a flow control device and are sized mostly on how much grease you will store between cleanings. They are smaller and often fit under a sink or in the floor nearby.
Gravity interceptors rely on time instead of hardware. Code generally requires 30 minutes of retention, which means a much larger tank. Larger tank usually means excavation. Excavation in an existing building usually means cutting a slab..
Which one you need is not a preference. It follows from your flow and your local code.
Sizing runs off:
Hours of operation
Meals served per hour
Grease produced per meal for your type of service
How often you plan to have the unit pumped
Grease stores at roughly six and a half to seven pounds per gallon, so the math turns into a tank size pretty quickly. If you undersize it, you are paying for a pump out every few weeks for the life of the lease. That is an operating cost you signed up for permanently.
Three rules from the construction side
Your three compartment sink and dishwasher connect to the interceptor. Your restrooms never do. Sanitary waste and grease waste are two separate systems. Mixing them is a violation and a mess.
Find out where the existing sanitary line is and how deep it runs before you commit to a space. A trap that has to sit below an invert you cannot reach is a very expensive discovery.
Ask the landlord in writing whether an interceptor already exists, what size it is, and whether you are sharing it with other tenants. Shared units create shared problems.
The lease stage question that saves the most money
Before you sign, ask the landlord these four things in writing:
Is there an existing grease interceptor serving this space?
What size is it, and what is its rated flow?
Is it shared with other tenants, and who pays for pumping?
Where is the sanitary connection, and at what depth?
Frequently asked questions
Does every restaurant need a grease trap? Effectively yes. Municipalities require grease interception for food service operations. The question is not whether you need one, it is what size and what type.
What is the difference between a grease trap and a grease interceptor? The terms are used interchangeably in conversation. In practice "trap" usually refers to a smaller hydromechanical unit near the fixtures, and "interceptor" usually refers to a larger gravity tank set below the floor or outside the building.
How often does a grease trap need to be pumped? On a schedule set by your local authority and by how fast your unit fills. An undersized unit can need service every few weeks. A correctly sized one is far less frequent, which is the entire argument for sizing it properly the first time.
Can a grease trap go above the floor? Smaller hydromechanical units often can, under a sink or nearby. Gravity interceptors generally cannot, which is why they drive excavation costs.
Do restrooms connect to a grease trap? No. Restroom waste is sanitary waste and stays on a separate system. Connecting it to grease waste is a code violation.
More in this series
Commercial Kitchen Code Requirements, in Plain English
If you are looking at a space and want a straight answer about what it will really take to open, take a look at how we handle Restaurant and Food Service Buildouts, or call us and we will walk the space with you before you sign anything.
