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Interceptors Frequently Asked Questions

Grease Interceptors

  1. Can an Fig. 8050 grease interceptor be supplied with a 6" inlet and outlet?
    Yes, but 6" connections would have serious adverse effects on efficiency.

  2. Can a cradle be supplied for a Slurry Interceptor?

  3. What GPM value should be used for a commercial dish washer to size a grease interceptor?
    You use the peak drain rate for the dish washer.

  4. Must the flow control device supplied with a G.I. always be installed?
    Yes. in order to insure proper flow and to permit air to intermix with the effluent to aid in the efficiency of the unit.

  5. How do you determine what size grease interceptor is needed?
    See the Procedure for Sizing Grease Interceptors section on page 8-01 in Smith catalog or refer to the "Sizing Interceptors According to PSI Standard" in our Technical Data for Interceptors section.
  6. Is a DX flange available for grease interceptors?

  7. Why must a flow control be used in the application with an interceptor?
    The flow control is the "Governor" for grease and oil interceptors. This control is insurance against overload of the interceptor under any drainage condition for maximum efficiency.

  8. What is the maximum recommended distance that a grease interceptor should be located from the last contributing fixture?
    25 feet

  9. What approvals do Jay R. Smith grease interceptors carry?
    Standard PDI-G101 Certification for 7 thru 50 gpm size units (Fig. 8007-8050)

  10. Can a flush mount unit in an above grade floor, suspended in the ceiling below, support itself?
    No. Even when an anchor/flashing flange is provided, independent support of the unit shall and must be provided. It is the responsibility of the installer to provide adequate support. The anchor/flashing flange is simply for locating the unit at a location in the poured slab to enable flush mounting with the floor and/or a device to attach the waterproofing material. The weight of the unit alone requires independent support. Once filled with water & grease the unit will triple its weight. This applies to units supplied with extensions and cradles. Independent support is also required of these. The independent support should be adequately attached to the building structure and approved by the structural engineer. Never rely on the small anchor flange on the unit and/or cradle to support itself.

  11. Does the standard Duco Coating resist corrosive soil if the unit is partially installed in the ground?
    No. Anytime a unit is installed fully or partially in the soil, a coal tar epoxy coating should be specified and ordered for the exterior of the unit. The units are fabricated from steel and corrosive soil will attack steel. Since most soil contains some corrosive elements, it is advisable to request the bitumastic coating. Bitumastic is a hard coating that is very durable and resists most corrosive soils. The standard Duco coating regularly furnished is fine for normal indoor installations.

  12. Why aren’t units available in cast iron anymore?
    The casting process to produce a cast iron unit is very expensive. Approximately 50% of the castings have to be scrapped. This combined with handling extremely heavy castings and a short life expectancy for expensive pattern equipment equates to an alternate material. This is where fabricated steel was desirable. The industry has not produced cast iron units for over 30 years.

  13. Is there a sizing formula for oil interceptors?
    Smith recommends point source sizing. If there are four hydrants which will be the only source of water and each hydrant flows 15 G.P.M., then the worst condition will be all four flowing at the same time. This requires a unit that will handle 60 G.P.M. Some codes require a safety factor be added to the total flow in the event a drum of oil is spilled. Most codes have their own requirements whether it is based on square footage, number of autos serviced, etc. If the local code has a sizing requirement, then it must be followed.
  14. How much P.S.I. will ten feet of head produce?

  15. Are units available in stainless steel?
    Yes. The majority of the units shown in the Smith ‘Yellow Pages’ catalog, Interceptor Section, can be fabricated from stainless steel.

  16. What is the largest size (in GPM) Grease Interceptor recognized by P.D.I.?
    50 G.P.M..

Grease+Gard II® Grease Recovery Device

  1. What does Grease+Gard II Retrofit Skimmer and/or Grease Recovery Device (GRD) do that a traditional grease interceptor doesn’t?
    Traditional grease interceptors must be manually cleaned by a professional with a vacuum truck (large interceptors), or by an employee by hand (small interceptors).
    The Grease+Gard II Retrofit Skimmer (installed on an existing grease interceptor) or a Grease+Gard II GRD will automatically remove fats, oils and grease from the interceptor at a pre-determined time. These devices require the grease collection container be emptied as needed.

  2. How does Grease+Gard II technology work?
    Free-floating fats, oils and grease are trapped in the grease interceptor. The Grease+Gard II device automatically skims the fats, oils and grease (commonly referred to as F.O.G.) out of the main interceptor chamber and into a collection container. Essentially, the intercepted grease is emptied much like having a professional clean your interceptor. Grease is removed from the interceptor and therefore unable to cause a back-up or overflow into drainage pipes.

  3. How do I dispose of grease collected by a Grease+Gard II device?
    Collected grease and oils are emptied into the grease-rendering barrel provided by your local rendering or disposal company. This is often the same barrel where you dump your deep-fryer grease. Rendering or disposal companies pick-up on a schedule and empty this container.
    NOTE: Before dumping grease into a landfill or garbage bin, please contact your local authority. Many municipalities have outlawed this practice.

  4. What happens to food and other solid materials that may go down the sink?
    Food scraps and other solid materials that may go down the sink drain are a hindrance to all forms of grease collection systems. Installing a solids interceptor between the sink and the grease interceptor will allow you to capture such scraps before they can cause havoc with the interceptor. Inline solids interceptors are easy to empty into a refuse container. Keeping solid waste scraps out of the interceptor adds the extra benefit of reducing odors and reducing the interceptor cleaning. Most odors are the result of rotting solids, not grease.

  5. What kind of maintenance is required for Grease+Gard II system?
    Sizing depends on two factors: the number of fixtures in your kitchen and the size of those fixtures in your kitchen. Contact us for a simple review and recommendation.

  6. How long does it take to install a Grease+Gard II Retrofit Skimmer?
    The average installation time will vary. However, one can normally expect less than two hours from start to finish.

  7. I have an outside, in-ground, grease interceptor; what can Grease+Gard II possibly do for me?
    By using the Grease+Gard II Retrofit Skimmer (installed on an existing grease interceptor) or by installing a Grease+Gard II Grease Recovery Device you are able to remove fats, oils, grease and solids before they get out of the kitchen area and into the in-ground interceptor. A Grease+Gard II system will protect the pipes between the kitchen and the outside interceptor. This will save you the expense of jetting the lines and because almost no grease is going to the in-ground interceptor, you will not have to pump out as often - again saving you money.