ARTICLE 9

USER REQUIREMENTS PART C:  INTERCEPTOR DESIGN AND INSTALLATION STANDARDS

9C1    GENERAL:  All work for design and installation of grease, sand or other type interceptors shall be performed in conformity with and are subject to the requirements and conditions set forth in Part B of Article 9.

9C2    ENGINEERING REVIEW  Three sets of plans and specifications, including complete mechanical and plumbing sections with interceptor detail and calculations shall be submitted to the District for review prior to construction.  Interceptor designs must meet the criteria set forth in the following paragraphs and in accordance with the appropriate sections in the District’s Rules and Regulations.

9C3    DESIGN STANDARDS  All designs shall conform to the Uniform Plumbing Code.  It is the Contractors and/or Customer’s responsibility to determine the adequate size of the interceptor.

1) The minimum size of the interceptor shall be determined by the maximum flow or expected maximum flow to the interceptor.

2) Where actual flow is unknown, expected flow can be determined by fixtureunit values from the Uniform Plumbing Code, or Plumbing and Drainage Institute.  Fixtureunit values are then converted to GPM discharge rates on the basis of one fixtureunit equaling 7.5 GPM discharge from the fixture.  Table 9C311 gives sample fixtureunit values and equivalent discharge flow.

Where applicable, flow may be on the maximum number of meals served at peak periods of the day.  Volume, in gallons, of the interceptors shall be 2½ times the number of meals served.

3) The flow to the interceptors shall not exceed 2½ times the certified gallons per minute flow rating of the given interceptor.

4) If flow to the interceptor is continuous, upsize the interceptor by 50%.

5) Any grease interceptor installed with the inlet more than four feet lower in elevation than the outlet of any fixture discharging into such interceptor shall have an approved rate of flow which is not less than 1½ times greater than the rated capacity.

6) Interceptors shall discharge to a storage tank.

7) Provide cleanouts and backwater valve for each installation.

8) Each interceptor shall be provided with an approved flow control or restricting device installed in a readily accessible and visible location in the inlet of each interceptor.

9) Flow control devices shall be designed such that the flow shall at no time be greater than the rated capacity of the interceptor.  No flow control device having adjustable or removable parts shall be approved.

10) Each flow control fitting shall be provided with an air intake/vent.

Table 9C311

9C4    INSTALLATION  Interceptors can be located inside or outside the building on private property.  All drains from the kitchen, food preparation, dish washing, and other similar type areas shall be connected to the appropriate interceptor.  Garbage grinders not connected to the grease interceptors shall not be used for disposal of grease.  All drains from automotive servicing areas will be connected to oil and sand interceptors.

1. It is not advisable to have a long horizontal run of piping, which is below the static water level in the interceptor.  All piping below this level will be filled with water and grease modules and the grease will solidify, plugging the pipe.  If a low inlet is used, provide adequate clean flushing water.
2. When using high inlets, note that gases from the interceptor may pass back through the drain opening.  An additional trap should be considered under the sink.
3. Where installations are set in a pit, provide grating or other removable cover for access.
4. Vent installation all flow control devices shall be connected to vent stack or vent not lower than the flow level of the highest drain serviced, or terminated in a return bend at the same elevation outside the building.  Intake air/vent shall terminate with elbow turned down.