5.1. Residential. Grease interceptors (grease traps) are not necessary or recommended for a residence. Drainage from kitchen sinks should be discharged through the plumbing system to the septic tank.

5.2. Commerical buildings. Grease interceptors are necessary on kitchen drain lines from institutions, hotels, restaurants, schools with lunchrooms, and other establishments from which a relatively high volume of grease may be discharged. Grease interceptor waste shall also be treated in the septic tank before being discharged into the disposal field. Consideration is to be given to the current edition of the ARKANSAS STATE PLUMBING CODE in this regard.

5.3. Garbage grinder waste. Waste from garbage grinders should not pass through any interceptor or grease trap before being discharged to a septic tank.

5.4. Specifications of grease trap materials. Grease interceptors, when used, shall be so designed and installed that they will not become air bound. A cover shall be provided and located so as to be conveniently accessible for servicing and cleaning the interceptor.

Grease interceptors shall be an approved manufactured type with proper efficiency rating and flow capacity.

5.5. Specifications of construction of grease traps. Grease traps installed on the outside of buildings, shall be of watertight construction, be inaccessible to insects and vermin, and shall be of metal, pre-cast concrete, constructed on the job of concrete or combined glazed tile and concrete.

Metal grease traps shall be coated inside and out with a heavy bituminized asphalt or coal tar coating.

Grease traps shall be constructed so as to ensure that both the inlet and outlet are submerged to properly trap the grease, and that the distance between inlet and outlet would be sufficient to allow separation of the grease, so that grease solids will not escape through the outlet.

The principles of the grease trap are illustrated in FIGURE 12.

5.6. Sizing the grease trap. Proper sizing of the grease trap should be based on efficiency ratings and flow capacities which are determined by the number and kinds of sinks or fixtures discharging into the trap.

Using the chart in TABLE 5, add the flow rates for all grease producing fixtures. Multiply this number by the required four (4) minute retention time. The result is the minimum grease trap size in gallons.

The minimum capacity of a grease trap, when installed in conjunction with a septic tank, shall not be less than 125 gallons. It is generally good economy to build grease traps somewhat oversized to reduce servicing costs.

5.7. Operation and maintenance of a grease trap. Grease traps, to be effective, must be operated properly and cleaned regularly to prevent the escape of grease solids into the septic tank.

Generally, the trap should be cleaned when 25 percent of the grease retention capacity is filled with accumulated grease. Experience will determine the frequency of cleaning.

Grease traps must be tightly covered to prevent odor and to exclude insects and vermin. Grease removed from a trap should be disposed of by procedures approved by the Department. It is essential to be thorough in cleaning the trap, the edges of the top, and around the trap, to allow a tight seal and not attract mice, rats and insects.