Illinois Plumbing Code Practice

A grease interceptor located on a floor below the fixture shall have what percentage of the liquid holding capacity of the fixture?

1. 30%

2. 45%

3. 60%

4. 75%

The correct answer is: 60%

The correct answer indicates that a grease interceptor located on a floor below the fixture should have 60% of the liquid holding capacity of the fixture. This requirement is based on the need to effectively capture and retain grease, oils, and solids that could otherwise accumulate in the plumbing system and create blockages or environmental hazards. The rationale for specifying a percentage is to ensure that the grease interceptor is adequately sized to handle the flow of wastewater, especially when situated below the fixture. Using 60% allows for proper retention time and effective separation of fats and oils from the wastewater. This can reduce the risk of overflow and ensure compliance with health and safety standards outlined in the Illinois Plumbing Code, ultimately maintaining the integrity of the plumbing system and preventing sewer backups. Other percentages, such as 30%, 45%, and 75%, are not specified in the code for this particular application, thus emphasizing that 60% is the optimal choice for grease interceptors in this situation.