Section 15.230 - Pretreatment Units - Grease Traps(1) Grease traps shall be provided for kitchen flows at restaurants, nursing homes, schools, hospitals and other facilities from which grease can be expected to be discharged.(2) Grease traps shall be installed on a separate building sewer serving kitchen flows into which the grease will be discharged. The discharge from the grease trap must flow to a properly designed septic tank or to a building sewer prior to the septic tank.(3) Grease traps shall have a minimum depth of four feet and a minimum capacity of 1,000 gallons, and shall have sufficient capacity to provide at least a 24-hour detention period for the kitchen flow. Kitchen flow shall be calculated in accordance with 310 CMR 15.203.(4) Grease traps shall be watertight and constructed of the materials specified in 310 CMR 15.221 and 15.226(1) and (2).(5) The inlet tee shall extend to the mid depth of the tank. The outlet tee shall extend to within 12 inches of the bottom of the tank. Tees shall be Schedule 40 PVC and properly supported by a hanger, strap or other device.(6) Grease traps shall be installed on a level stable base that has been mechanically compacted and onto which six inches of crushed stone has been placed to minimize uneven settling.(7) Grease traps shall be provided with a minimum 20-inch diameter manhole frame and cover to grade over the inlet and outlet tees.(8) Grease traps shall be accessible for inspection and maintenance. No structures shall be constructed directly upon or above the grease trap access locations.(9) The invert elevation of the inlet of a grease trap shall be at least two inches above the invert elevation of the outlet. The inlet and outlet shall be located at the center line of the tank, and at least 12 inches above the high groundwater elevation.(10) Backfill around the grease trap shall be placed in such a manner as to prevent damage to the tank.(11) Grease traps shall be maintained in accordance with 310 CMR 15.351.(12) Grease removal by other devices located within the building as part of the internal plumbing are not within the jurisdiction of 310 CMR 15.000, shall not be considered for compliance with 310 CMR 15.230 and shall comply with the State Plumbing Code. Grease removal devices located outside of the building, other than those in compliance with 310 CMR 15.230, require the prior written approval of the Department.(13) The Approving Authority may require that alarms and/or remote monitoring devices be installed and connected to grease traps.