Getting greasy in the corner

In this edition of Quattro’s Corner, I’ve asked Canplas Industries’ separation technologies product manager Rachel Beaulieu to help me out as we take a look at grease interceptors.

As you know, the purpose of a grease interceptor is to prevent fats, oil and grease (also know as FOG) from entering the sanitary drainage system. Without these interceptors your local sewage treatment plant would have to deal with the excess FOG, and the building would likely suffer from serious maintenance problems due to clogging and the inevitable circumstance of completely blocked drainage pipes.

There are three main types of grease interceptors on the market today, each with its own method of separation, and strengths and weaknesses.

Ontario’s code requires a 1-1/2” or larger vent pipe to be connected to the outlet pipe connected to the plumbing venting system, and every vent pipe that serves an oil or grease interceptor and is located outside a building needs to be at least 3” in areas where it may be subject to frost closure.

A vent pipe must be no more than l,500 mm from the interceptor inlet and must have a cleanout.

The most interesting difference between the Ontario Building Code and The National Plumbing Code of Canada is that the Ontario code requires every fixture to be separately trapped and does not permit a grease interceptor to act as a fixtures trap. In the National Plumbing Code of Canada, however a grease interceptor is permitted to act as a fixture trap, provided that the interceptor has an effective water seal of not less than 38 mm.

Let’s go to the codes

In my home province of Ontario, the Ontario Building Code talks about interceptors in sections 7.2.3.2 and 7.4.4.3.

Here, we see that interceptors need to be built in a way that allows for them to be readily cleaned and not get air bound, and that with the exception of residential builds, interceptors are required “…where a fixture discharges sewage that includes fats, oils or grease and is located in an area where food is cooked, processed or prepared…”

That interceptor, which must conform to either CSA B481.1 or CSA B481.2, needs to be as close as possible to the fixture(s) it is serving, and the flow rate through it must not exceed its rated capacity.

The code book actually includes a set formula for calculating the flow rate, but you will be happy to know that most manufacturers that make this equipment have calculators online. These calculators are very simple to use: punch in a few numbers, give a drain-down time, and “Bam,” the size and model of interceptor is provided for you. It may be interesting to note that Ontario requires all grease and oil interceptors to have an internal flow control and, where the head will exceed five feet, a secondary flow control. No such requirements are located in the National Plumbing Code of Canada. The National Building Code of Canada outlines interceptor requirements in sections 2.2.3.2 and 2.4.4.3.

Like in Ontario, they need to have the ability to be readily cleaned, and be designed so that they do not become air bound, but they can also not have a water jacket.

The Canadian code cites CSA B481.0 and CSA B481.3 for their selection and installation.

In addition, the Canadian code states that “Where a fixture discharges sewage that includes fats, oils or grease and is located in a public kitchen, in a restaurant or in a care or detention occupancy, it shall discharge through a grease interceptor.”

Andrew Quattrociocchi, C.B.C.O., is the deputy chief building official for the Township of Oro-Medonte, and a director with the Ontario Plumbing Inspectors Association. If you have any questions or a funny photo you would like to possibly see in an upcoming edition of Quattro’s Corner, feel free to send an email to Andrew at quattroscorner@hotmail.com