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The problem with flushing cooking grease

Grease build-up is the number one cause of sewage back-ups in restaurants, resulting in immediate restaurant closure. It can also cause your neighbours’ basements to flood.

Grease trap installation and maintenance is mandatory wherever food is cooked, processed or prepared under the Ontario Building Code 350.06.

Enforceable through penalties and fines, there are limits in Schedule A of By-law No. 2008-192 (“The Sewer Use By-law”) that prohibit the discharge of grease and oil over 150 mg/l.

It is costly and time-consuming to return the sewer back to normal after a grease blockage and sewage back-up. The related costs incurred by Utilities Kingston could be charged back to the restaurant or food service operations. Additionally, the health inspector will close the restaurant and any restaurants upstream of the blockage until water usage can resume. This could take an entire day.

Keep grease out

Restaurants and food service operations account for a high percentage of the grease accumulation in our sewers, and the resulting blockages and back-ups. Major sources of grease are baking goods, lard, food scraps, cooking oil, shortening, butter, creamy sauces, dairy products (e.g., milkshakes), meat fats, batter and gravy.

Grease traps

Grease traps and interceptors are containment units designed to trap grease, oil, solids, and other debris. They prevent these substances from getting into the sanitary sewer system where they can eventually block the entire pipe.


To be effective, grease traps and interceptors must be installed, operated, and maintained in accordance with the manufacturer’s instructions, and must be inspected and cleaned frequently to ensure that they are operating effectively. When cleaning the grease trap/interceptor yourself, scoop out the solidified grease portion on the top and place in the garbage or composter for disposal. Place the liquid portion in a sealable container. Used cooking oil can be recycled (for example, through a third-party recycling facility) and storage bins can be rented from cooking oil recyclers. You may also choose to seek services from a certified and licensed grease removal contractor.


Keeping a logbook of all cleanouts, either by you or a contractor, along with receipts from the contractor, will help you maintain a grease trap/interceptor cleaning schedule. It’s also a requirement of the Sewer Use By-law that the maintenance activity is recorded. Records must include the following:

  • the dates on which cleaning or maintenance occurred
  • the person or contractor responsible
  • the method and destination of waste disposal

Proper grease disposal practices

  • Place screens over drains
  • Wipe grease from dishes and pots using paper towel
  • Recycle used oil (for example, through a third-party recycling facility)
  • Train employees on grease trap maintenance
  • Scrape food scraps and grease into the garbage or composter
  • Check and clean grease traps often
  • Never pour grease down drains or toilets
  • Do not use degreasers, emulsifiers, or hot water to dissolve grease – these approaches may move the FOG further down the pipe, but they do not treat or eliminate the problem
  • Never pour grease straight into the garbage dumpster