Sewer Use and Drainage Permits (SUDP)

NEW FACILITIES

The minimum volume for a gravity two-compartment grease interceptor is 800 gallons and must service the entire commercial kitchen. No single point of use pretreatment device will be allowed. The volume of an adequately sized solids and/or grease interceptor (GI) to handle the non-domestic waste stream originating from a commercial kitchen such as a restaurant is primarily based on the number of seats where meals are served (meal production), the type of food items presented on the menu and the number and type of each cooking appliance to be installed in the kitchen. The plumbing plans for establishments with commercial kitchens must show all plumbing fixtures and drains that are within the vicinity of cooking equipment in the food prep, cookline and ware washing areas of the kitchen being routed to the interceptor. Areas of the establishment that are outside the commercial kitchen where no solids/grease waste is generated i.e. bars, beverage stations, wait stations, restroom, etc. are routed directly to the building domestic sanitary waste system.

Additional notes and guidance on the information to provide for the calculated sizing of the interceptor can be found on the GI sizing calculator cover page. Locations with existing interceptors will be required to have it inspected for condition and size prior to approval.

Retail/Wholesale Food Establishment Application(PDF, 562KB)

Grease Interceptor Sizing Worksheet(XLSM, 153KB)
(Requires Microsoft Excel Version 2003 or later)

Grease Interceptor Sizing Criteria(PDF, 136KB)

*Updates as follows since date of approved document GI Requirements Update P-400-501

1. Any use of the referenced UPC Appendix H is for variance requests only.
2. See Building Codes, Policies and Guides page for the current adopted I-Codes and Denver Building Code amendments.

The City and County of Denver utilizes the two-compartment gravity grease interceptor which can be found under our Standards and Details Tab below. All projects are required to use the standard two-compartment concrete detail and is to be added to your plans submitted for review.

Any deviation from the standard detail is subject to further review and approval from the DOTI Wastewater Variance Committee. To request a variance, please provide the following in your initial submittal or resubmittal:

1. A completed variance application(PDF, 269KB).
2. A letter signed by the owner outlining the reasons for the request. Please note that cost is not a hardship.
3. Any additional plans or documents supporting your request.

A formal letter of approval or denial will be emailed to the owner from your reviewer after review of the variance request. Variances are reviewed by the committee weekly and are responded to within one week of decision.

For those kitchen facilities that generate no or minimal amounts of grease/solid waste, a variance to a grease interceptor may be granted by the plan reviewer at their own discretion. Your reviewer will determine if you qualify for an automatic variance during review. Possible examples include facilities that serve prepackaged food, drinks, etc. for sale or consumption.

EXISTING FACILITIES

Every existing establishment with a commercial kitchen undergoing a change in the mode of operation will include a pre-treatment device review to provide adequate protection to the public sanitary sewer system from solids and/or grease waste accumulation based on the following scope of work modifications to the existing establishment:

• ownership
• business name
• process (preparation and cooking)
• menu
• seating capacity
• additional or change in equipment and/or space

The existing facilities will undergo the same reviews as noted above for new establishments. Location with existing interceptors will be required to have it inspected for condition and size prior to approval.

What is Denver Wastewater's Standard Grease Interceptor Detail?
See www.denvergov.org/sudp at the bottom of the page, select Standards & Details, 2 Compartment Grease Interceptor. Per CCD Standards, two-compartment, gravity only interceptors are allowed.

Does the interceptor have to be concrete or is the use of non-concrete material allowed?
Per the CCD Wastewater interceptor standard detail, all interceptors are required to be made out of concrete. For variances, please submit information on the type of material you wish to use in your variance request.

What is a hydromechanical or proprietary interceptor?
Proprietary interceptors are specific to one manufacturer and are often hydromechanical. Hydromechanical interceptors are devices that use hydromechanical separation, interior baffling and air entrainment barriers, whether in combination or independently, to separate and retail oil and grease solids from wastewater.

Are hydromechanical or proprietary interceptors approved in Denver?
Yes, through a variance request process. Please see Food and Beverage Establishment guidelines above for more information.

Do you have an approved list of hydromechanical or proprietary interceptors that are approved?
No, not at this time. Please submit information on the device you wish to use in your variance request.

Do you permit interceptor configurations with multiple interceptors?
Yes, however they must be in parallel not in series even if recommended or allowed by a specific manufacturer if your device is approved through a variance. A flow control valve will be required upstream of the interceptor configuration to ensure flow to all interceptors.

Are single point/at fixture interceptors allowed?
No, they are not allowed for any facility that is required to have an interceptor.

Retail/Wholesale Food Establishment Application(PDF, 562KB)

Grease Interceptor Sizing Worksheet(XLSM, 153KB)
(Requires Microsoft Excel Version 2003 or later)

Grease Interceptor Sizing Criteria(PDF, 136KB)

What if the sizing criteria and worksheet states that my required interceptor capacity is oversized compared to my designer's recommendations?
Double check the square footage used. Do not include the entire facility, only the dining areas. Don't count dishwashers in bar areas. Use of the UPC Appendix H as allowed in Denver's Sizing Criteria is permitted in variance situations only.

What other sizing criteria can I use? Can I use the current year International Plumbing Code (IPC) calculations?
No. The current adopted IPC is amended by the Denver Building Code amendments replacing the sizing criteria with a reference Denver Wastewater standards and sizing criteria. Alternative sizing may be used in a variance request.

What if I install a size other than what my plans were approved for?
The approved minimum size is based upon the review completed and approval granted. Exceeding the minimum is permitted. If the mode of operation has changed, a supplemental review can be completed to update the required minimum size GI for the project. Otherwise, the original required capacity is to be installed.

I have a tenant finish that is proposing a grease interceptor, but I am being asked to remove it. Why?
In general, it is because the interceptor location or type is not approved for use. Projects that do not require an interceptor will be asked to remove it unless approved by variance.

How do I size for a future unknown restaurant use and I want to install the interceptor now under a core/shell permit?
Core/Shell installations of an interceptor come with an acknowledged risk. It is recommended to consult with your designer and determine the size of the space and possible fixtures for each space that will potentially use an interceptor. The online interceptor sizing worksheet (see below) can help determine potential minimum capacity(ies) needed. The interceptor should meet the needs of all spaces.

Can I share the same interceptor with another facility in the same building/strip mall? If so, how do I size it? If not, why?
Yes, an interceptor can be shared by multiple units. Sizing of the interceptor must account for all spaces. If the existing interceptor is at capacity, an addition or new interceptor will be required.

Do I need to install a solids interceptor?
One is not required but highly recommended for downstream of a disposal/food grinder and for optimal use of the interceptor. If a proprietary interceptor is approved, the manufacturer's recommendations shall be followed for any solids interceptor.

Why do I have to install an interceptor?

• It was identified during review that the facility's proposed mode of operation requires an interceptor be installed to eliminate/remove fats, oils, and grease prior to discharging waste from the facility to the public main.
• The existing interceptor is undersized or not suitable for reuse as determined by the CCD Wastewater inspections team.
• The existing interceptor is shared by multiple tenants and is at capacity.

Does my type of restaurant required a grease interceptor?
Final determination is made during review of the project. For those kitchen facilities that generate no or minimal amounts of grease/solid waste, a variance to a grease interceptor may be granted by the plan reviewer at their own discretion. The SUDP reviewer will determine if the project qualifies for an automatic variance during review. Possible examples include facilities that serve prepackaged food, drinks, etc. for sale or consumption. Some variances are reviewed by the variance committee only.

My facility uses milk in our process - is pretreatment required?
Pretreatment, including sampling, may be required depending on the volume of milk used or produced. A solids interceptor is recommended but final determination is made during review.

Is a sampling port required downstream of an interceptor?
In general no, but it may be required for locations with multiple tenants as determined by our Quality Control department during review. Installation is allowed if desired when not required.

How do I call for inspections?
Please refer to your review comments, the inspections section of your issued SUDP, and the Wastewater Inspections Sections on this page.

What is the minimum pipe size for the interceptor inlet and outlet pipes?
Four inch (4") is the minimum pipe size and must be consistent between both the inlet and outlet pipes.

Where can I install a grease interceptor?
Preferred locations are on the exterior of the structure, on private property and below grade. Interior locations to be approved by DDPHE but in general may not be in areas of food prep, cooking, or dish washing.

Can I use an ejector for my grease waste?
Ejectors are not allowed upstream of any interceptor, grease or solids. Ejectors downstream will need to provide justification as all fixtures that can drain by gravity must drain by gravity.

SUDP invoices must be paid prior to December 31 of the invoice year. Additional fees at the new year's rate may be assessed and payment required for any prior-year invoices.

Wastewater Sewer Use and Drainage Permit (SUDP):

• Sewer Tap Permit Fees for 2025(PDF, 452KB)
• Sewer Tap Permit Fees for 2024(PDF, 306KB)

For information on standard fees, see DOTI / SUDP on the Building and Land Development Fees webpage.

The following technical documents are sample design standards:

• Grease interceptor(PDF, 54KB)
• Single Compartment Sand Oil Interceptor(PDF, 172KB)
• 2 Compartment Sand Oil Interceptor(PDF, 65KB)
• Residential Drainage(PDF, 56KB)
• Sideyard Drainage(PDF, 134KB)
• Sanitary Cleanout Detail Figure 2.11.1(PDF, 421KB)

The following technical documents can be downloaded from Department of Transportation & Infrastructure, Right of Way Services page Manuals and Regulations or Document Center.

• Sanitary design and technical criteria manual 
• Sanitary sewer master plan
• Storm drainage design and technical criteria manual 
• Storm drainage master plan
• Wastewater detail and technical specifications 
• Wastewater standard detail drawings

Set up your inspections for all your Wasterwater sewer use and drainage permits (SUDP).

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