The following standards of construction are applicable to new external, in-ground grease interceptors, Please refer to the drawing for reference:
(a) All grease interceptor design plans shall be approved by the city prior to construction.
(b) Wastewater from sanitary facilities (bathrooms, non-kitchen sinks) shall not be introduced into any grease interceptor.
(c) All dishwater drain lines or floor drains shall have permanently fixed screens with maximum 1/4 inch openings to prevent pass through of large solids into the grease interceptor.
(d) An inlet tee should be constructed to disperse influent wastewater in the first chamber to avoid hydraulic short-circuiting and disrupting the grease separation process. The inlet tee should extend 12 to 16 inches below the static water level.
(e) A baffle wall with two (2) 6-inch baffle wall tees shall be placed approximately 2/3rds of the length of the grease interceptor to create a first chamber for solids settling and grease flotation, and a second chamber for wastewater discharge and sampling. The baffle wall shall be connected to the bottom of the tank and allow an air gap at the top of the tank. The 2 baffle tees shall not extend greater than 30% below the static water level in the first chamber.
(f) A minimum 6-inch outlet tee should be constructed extending no greater than 50% below the static water level. The outlet tee should allow for a dip-and-grab sample to be taken for laboratory analysis. The elevation differential between the inlet and outlet tees shall be 2 inches.
(g) The top slab of the grease interceptor shall have minimum 24" access openings installed at grade to allow access to the grease interceptor’s inlet tee and outlet tee. If placed in a driveway, parking lot or other traffic area, the entire grease interceptor shall be highway (H-20 load) rated.
(h) All grease interceptor joints shall be properly sealed using mastic, butyl rubber or other pliable sealant that is waterproof, corrosion-resistant and approved for use in septic tanks.
(i) In addition to the grease interceptor, a separate ‘sample vault’ may also be constructed for more accurate effluent monitoring if preferred by the FSE.
(j) A licensed North Carolina plumbing contractor shall install the grease interceptor in compliance with the latest edition of the Uniform Plumbing Code.
(k) Approved internal under-the-sink or in-flbor grease traps shall be sized to maximize hydraulic retention time and grease storage. These units shall be installed by a licensed North Carolina plumbing contractor.
(Ord. of 11/7/11, No. 07-11)