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. For more information, please visit

Text of Grease Myths & Facts by PDI

  • 1. Presented by Rand Ackroyd Copyright PDI 2008

2. Plumbing and Drainage Institute The Plumbing and Drainage Institute(PDI) was formed in 1949. The organization developed the originalperformance requirements for GreaseInterceptors (Hydromechanical GreaseInterceptors) PDI G101. Copyright PDI 2008 3. Plumbing and Drainage InstituteOur objectives: Advancement of Engineered PlumbingProducts Publicity/Public Relations Research Publish Standards Education Copyright PDI 2008 4. GREASEHow Bad Can It Be? 5. Myth: If grease is not used in foodpreparation a grease interceptor is notneeded. Fact: Grease is not the only problem. Theoverall problem is FOG (Fats, Oils andGrease). These materials alone or incombination will result is sewer blockages. Copyright PDI 2008 6. Myth: Choosing a larger size greaseinterceptor will result in a greater greaseremoval efficient. Fact: When grease interceptor has beensized properly to the anticipated maximumflow using a grease interceptor with a largerflow capacity will not increase greaseremoval efficiency.Copyright PDI 2008 7. Myth: The larger the grease storage, themore efficient the interceptor. Fact: Grease must be separated from thewaste water before it can be stored.Storage capacity and grease removalefficiency are not related. Copyright PDI 2008 8. Myth: The grease must cool and harden toseparate from the waste water. Fact: Grease interceptors separate based onthe difference in specific gravity of FOG andwater. Liquefied grease floats just as well assolidified grease. Grease is lighter thanwater.Copyright PDI 2008 9. Myth: Hot water will melt the grease andwash the grease through the interceptor. Fact: All hydro mechanical greaseinterceptors are tested for grease removalefficiency with 150F water.Copyright PDI 2008 10. Myth: Once the grease is captured in theinterceptor, it will remain captured in theinterceptor as long as the interceptor is notyet 25% full. Fact: Because the grease (FOG) iscontaminated with food particles and theinterceptor is a breeding ground for bacteria,the FOG can be broken down, exit theinterceptor and create blockagesdownstream.Copyright PDI 2008 11. Myth: Over sizing an interceptor cannothurt. Fact: Over sizing an interceptor relative toactual flow is a problem. It can result in thegeneration of hydrogen sulfide gas that canconvert to hydrochloric acid. Both metaland concrete structures downstream havesuffered severe structural damage fromthis acid. Copyright PDI 2008 12. Myth: With the change to healthier cookingoils, there is less of a FOG problem. Fact: Cooking oils that are healthier for youare not healthier for the drainage system.They are all polar hydrocarbons. In fact,some of the new alternative cooking oilswith specific gravities closer to water willbe harder to capture from the wastewater. Copyright PDI 2008 13. Myth: When the grease interceptor is full,the drain line will stop flowing. Fact: Water will continue to flow even whenthe FOG in the interceptor is at capacity.Additional grease in the wastewater willsimply flow right through the interceptor.Grease interceptors must be eithermanually or electronically monitored.Copyright PDI 2008 14. Myth: Grease does not clog plastic pipe Fact: Grease can create blockages all aldrain pipe materials. Copyright PDI 2008 15. Thank You For Your Time! Copyright PDI 2008