Grease Myths & Facts by PDI


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A presentation by Rand Ackroyd, of the Plumbing and Drainage Institute, sorting out grease myths and facts.

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Grease Myths & Facts by PDI

  1. 1. Presented by Rand Ackroyd Copyright PDI 2008
  2. 2. Plumbing and Drainage Institute• The Plumbing and Drainage Institute (PDI) was formed in 1949.• The organization developed the original performance requirements for Grease Interceptors (Hydromechanical Grease Interceptors) PDI G101. Copyright PDI 2008
  3. 3. Plumbing and Drainage InstituteOur objectives: – Advancement of Engineered Plumbing Products – Publicity/Public Relations – Research – Publish Standards – Education Copyright PDI 2008
  4. 4. GREASE…How Bad Can It Be?
  5. 5. • Myth: If grease is not used in food preparation a grease interceptor is not needed.• Fact: Grease is not the only problem. The overall problem is FOG (Fats, Oils and Grease). These materials alone or in combination will result is sewer blockages. Copyright PDI 2008
  6. 6. • Myth: Choosing a larger size grease interceptor will result in a greater grease removal efficient.• Fact: When grease interceptor has been sized properly to the anticipated maximum flow using a grease interceptor with a larger flow capacity will not increase grease removal efficiency. Copyright PDI 2008
  7. 7. • Myth: The larger the grease storage, the more efficient the interceptor.• Fact: Grease must be separated from the waste water before it can be stored. Storage capacity and grease removal efficiency are not related. Copyright PDI 2008
  8. 8. • Myth: The grease must cool and harden to separate from the waste water.• Fact: Grease interceptors separate based on the difference in specific gravity of FOG and water. Liquefied grease floats just as well as solidified grease. Grease is lighter than water. Copyright PDI 2008
  9. 9. • Myth: Hot water will melt the grease and wash the grease through the interceptor.• Fact: All hydro mechanical grease interceptors are tested for grease removal efficiency with 150°F water. Copyright PDI 2008
  10. 10. • Myth: Once the grease is captured in the interceptor, it will remain captured in the interceptor as long as the interceptor is not yet 25% full.• Fact: Because the grease (FOG) is contaminated with food particles and the interceptor is a breeding ground for bacteria, the FOG can be broken down, exit the interceptor and create blockages downstream. Copyright PDI 2008
  11. 11. • Myth: Over sizing an interceptor cannot hurt.• Fact: Over sizing an interceptor relative to actual flow is a problem. It can result in the generation of hydrogen sulfide gas that can convert to hydrochloric acid. Both metal and concrete structures downstream have suffered severe structural damage from this acid. Copyright PDI 2008
  12. 12. • Myth: With the change to healthier cooking oils, there is less of a FOG problem.• Fact: Cooking oils that are healthier for you are not healthier for the drainage system. They are all polar hydrocarbons. In fact, some of the new alternative cooking oils with specific gravities closer to water will be harder to capture from the wastewater. Copyright PDI 2008
  13. 13. • Myth: When the grease interceptor is full, the drain line will stop flowing.• Fact: Water will continue to flow even when the FOG in the interceptor is at capacity. Additional grease in the wastewater will simply flow right through the interceptor. Grease interceptors must be either manually or electronically monitored. Copyright PDI 2008
  14. 14. • Myth: Grease does not clog plastic pipe• Fact: Grease can create blockages all al drain pipe materials. Copyright PDI 2008
  15. 15. Thank You For Your Time! Copyright PDI 2008