Grease Interceptor Corrosion

As fats, oils and grease (FOG) break down in an interceptor, anaerobic bacteria convert naturally occurring sulfate molecules into sulfides, which form hydrogen sulfide gas (H₂S) in the free air space of the interceptor. Airborne aerobic bacteria consume hydrogen sulfide gas and convert it into sulfuric acid (H₂SO₄) in the wastewater of the interceptor.

Why does it matter?

These compounds travel down into the sewer system creating what the British lovingly call FATBERGS! Both metal and concrete are guaranteed to fail over time due to these chemical reactions.

An industry study shows that FOG deposits found in collection systems were made up of Calcium and Iron from hard water, concrete and steel corrosion.  Another contributing factor found is non-flushable wipes that combine with FOG to further create Sanitary Sewer Overflows.

• Bentonville, AR - "Constructed of non-corrosive material, such as HDPE & Thermo-plastic. Concrete and Metal Fabricated interceptors will not be allowed."

• Columbus, OH - "The designed service interval shall not exceed 30 days between services for concrete gravity units or 90 days between services for units constructed of materials resistant to degradation associated to the pH levels in the effluent or the hydrogen sulfide gas byproducts."

• Flagstaff, AZ - "GGIs are recommended to be made from materials that are compatible with a pH of 3 to preserve the integrity and longevity of the interceptor. GGIs made from materials that are subject to corrosion such as concrete or steel, should be lined or coated with a durable material approved by the City that is compatible with a pH of 3 and that cannot be easily penetrated, scraped away or removed."

• Hampton Roads Sanitation District, VA - "GGIs shall be made from materials that are compatible with a pH of 3. GGIs made from materials that are subject to corrosion such as concrete or steel, shall be lined or coated with a durable material compatible with a pH of 3 that cannot be easily penetrated, scraped away, or removed as approved by the sanitary sewer system owner. Acid Resistant Enamel (ARE) coatings are not acceptable."

• Miami/DERM - "The material of the interceptor shall also be compatible with a pH of 3.0."

• Peoria, AZ - "All pretreatment devices must be constructed of non-corroding materials. Concrete or metal devices are prohibited for installation in food and/or beverage service, preparation, or handling establishments, or in any application where the surroundings and/or contents will cause any degradation of the interceptor or associated plumbing."

• York Sewer District, ME - "All Grease Interceptors shall be made from materials that are compatible with a pH of 3. Grease Interceptors that are made from materials that are subject to corrosion such as concrete or steel, shall be lined or coated with a durable material approved by the District that is compatible with a pH of 3 and that cannot be easily penetrated, scraped off or removed. Acid Resistant Enamel coatings (A.R.E) are not allowed."