Commercial Pretreatment

Requirements For Commercial Facilities

Commercial PretreatmentGrease interceptors are required in following commercial facilities:

  • Restaurants- All types, Fast food. Pizza delivery, Sandwich shop, Bakeries.
    Learn about Best Practices for Fats, Oils and Greases
  • Services Stations- Auto repair, Car washes, Fuel Stations
  • Pet Grooming, Salons- Hair traps
  • Laundries- Lint/Hair traps
  • All photo processing facilities, dental offices, and x-ray processing facilities shall be equipped with a metal recovery unit
For additional information about these requirements, please of the Surprise Municipal Code.
  1. Grease Interceptor
  2. Oil & Sand Interceptors
  3. HGI Interceptor

Do you need to install a Grease Interceptor?

Types of fixtures that require a grease trap / interceptor

  • 3 - compartment sink
  • pre-rinse sink
  • mop/floor sink
  • dishwasher machine floor drain
  • wash stations
  • flow through and floor drains with grease laden potential

Types of fixtures that do not require a grease trap or interceptor

  • hand sinks
  • ice machines
  • bathroom floor drains
  • water fountains
  • soda machine drainage

Do not discharge the following fixtures to grease trap or interceptor

  • Restroom facilities such as toilets Urinals and other similar sanitary fixtures
  • Hot liquids

Grease interceptors within the city shall be:

  • outside installation
  • accessible for cleaning and inspections
  • minimum of 750 gallons and a maximum of 2500 gallons
  • installed and maintained per the manufacturers specifications
  • appropriate traffic rated covers

*The type of food served and preparation methods employed shall be taken into consideration.

What size Grease Interceptor should be installed?

 Fixture Outlet or Trap Size
Drainage Fixture Unit Value
 GPM Equivalent
 1 1/4
1 1/2
2 1/2
Floor Drains - All
2x Trap Arm Size


  1. Determine total Fixture- Unit Value by multiplying fixture type count by the drainage value.
  2. Total all values.
  3. Determine total flow by multiplying total value by flow rate of 3 GPM.
  4. Multiply total flow by 12 if no garbage disposal unit is used.
  5. Multiply total flow by 17 if garbage disposal unit is used.
  6. Round to the next nearest size interceptor – (minimum 500 gallons not to exceed 2500 gallons)


 Type of Fixture
 Fixture Count
 Size  Fixture-Unit Value
3 comp sink
1 2 1/2"
4 4
Mop Sink
 1 3" 5 5
Floor Sink
2 2" 3 6
Floor Drain
4 N/A 2 8
Total Fixture units
Multiply by 3 GMP Flow Rate
Total GMP Flow Rate
Multiply by either 12 or 17
without or with garbage disposal unit
Size of Interceptor calculated
Round up to next available size

City of Surprise Guidance for Grease Interceptors

Large interceptors cause long-term issues where odor and gases build up in the sewer and become exposure issues for crews lifting manhole covers located downstream of large interceptors. These gases can pose an immediate danger to health and life (IDHL).

Interceptors Shall Be:

  • 750 gals or larger for 3 compartment interceptor
  • Installed according to manufacturers specifications. Appropriate rated covers
  • No more than 2 restaurants per interceptor with under sink trap units installed
  • Two smaller interceptors are required once the size reaches over 2500 gallons

Grease Trap in Lieu of Grease Interceptor

The following are examples of those facilities that may install a grease trap in lieu of a grease interceptor with appropriate calculations performed, submitted and sealed by a State of Arizona Certified Professional Engineer
  • Delicatessens
  • Sandwich shops
  • Coffee shops
  • Pizzas take out and bake with no inside service pizza only and no fryers
  • Ice Cream shops (ice cream or yogurt may not be made on premises and all ware must be disposable)
*These facilities must have limited preparation of pre-cooked meals/food, minimal cooking or making of foods, food preparation and where minimal cleanup from food service would take place.

*These facilities must not have a type one hood instillation.