Interceptors

1.1.3.2. Definitions

Interceptor means a receptacle that is designed and installed to prevent oil, grease, sand or other materials from passing into a drainage system.

7.1.7.2.(1)

Every fixture, plumbing appliance, interceptor, cleanout, valve, device or piece of equipment shall be so located that it is readily accessible for use, cleaning and maintenance.

7.2.3.2.

Every interceptor shall be designed so that it can be readily cleaned.
Every grease interceptor shall be designed so that it does not become air bound.

Grease Interceptors

There are two kinds of grease interceptors:

Manufactured Unit

manufactured grease interceptor

Built On-Site Grease Interceptors

7.4.4.3.(6):

An on-site constructed interceptor shall be constructed to the requirements of a manufactured interceptor.

on-site interceptor

Principles of Operation

Using specific gravity is the operating principle for interceptors. As discharge drains into the interceptor it passes through a flow control fitting located on the inlet and slows down. This slowing down gives the natural process of separation. The water also passes over a series of baffles, which further facilitates the process of separation by breaking up the flow. Finally, the grease free water is then discharged through an outlet located near the bottom of the tank, that is below the surface level of the grease.

grease interceptor

flow control fitting

Flow Control Fitting

7.4.4.3.(9):

All grease interceptors shall have an internal flow control and where the head will exceed five feet, a secondary flow control shall be required.

As we see, the device is simply a plate with a hole drilled in it.

7.4.4.3.(1):

Except for suites of residential occupancy, a grease interceptor shall be required anywhere that food is cooked, processed or prepared.

7.4.3.3.(1):

Except as provided in Sentence (2), garbage grinders, potato peelers and other similar types of equipment shall not be located upstream of an interceptor.

Food Scrap Interceptor

7.4.3.3.(2):

If a food scrap interceptor has been installed upstream of the grease interceptor, garbage grinders, potato peelers and other similar equipment may discharge through a grease interceptor.

7.5.4.2.(9):

Every vent pipe serving an oil or grease interceptor that is located outside a building shall be a minimum 3" size.

7.5.4.2.(3)

Every grease interceptor shall have a vent pipe that is at least 1 1/2" size connected to the outlet pipe, that connects to the plumbing venting system.

A grease interceptor shall be located as close as possible to the fixture or fixtures it serves.

7.4.4.3.(7)

A grease interceptor shall be located as close as possible to the fixture or fixtures it serves.

7.4.5.1.(5)

A grease interceptor shall not serve as a fixture trap and each fixture discharging through the interceptor shall be trapped and vented.

7.5.4.2.(4)

A vent pipe shall be provided within 1 500 mm of the inlet a grease interceptor complete with a cleanout to provide cleaning of the pipe.

7.4.7.1.(8)

A cleanout shall be provided to permit the cleaning of piping immediately downstream of the grease interceptor.

Grease Interceptor Dimentions

7.4.4.3.(8):

The flow rate through a grease interceptor shall not exceed its rated capacity and the flow rate shall be determined using the following:

Where Q is the flow rate to a grease interceptor in L/s.

Where V is the volume of the fixture in L.

Where DDT is the drain down time, 60 or 120 seconds (1 or 2 minutes).

Where PD is any pump discharge in L/s.

Where N is the number of fixtures to go through the interceptor.

Example

Determine the size of a grease interceptor serving a double bowl commercial kitchen sink. Each bowl measured 900 mm x 450 mm x 300 mm.

Calculate the capacity of each bowl in liters:

900 mm x 450 mm x 300 mm = 121,500,000 mm3 per bowl,

121,500,000 mm3 / 1,000,000 mm3 = 121.5 L per bowl,

121.5 L x 2 = 243 L total capacity of the sink.

Convert the total capacity of the sink into liters per second flow.

Maybe someone prefers to use table A - 7.4.4.3.(8) to do this, but I think it only makes unnecessary confusion. Why not to use the formula instead?

0.75 x 243 / 60 = 3.0375 L/s or x 60 = 182.25 L/min Total Flow Rate

If there is a pump discharging through the grease interceptor, add pump discharge according to the formula, but you need to know it first.

Sediment Interceptor

7.4.4.3.(4)

Where fixture discharges sand, grit or similar materials, an interceptor designed for the purpose of intercepting such discharges shall be installed.

There are no vent requirements for sediment interceptors.

Oil Interceptors

there are two kinds of oil interceptors:

Manufactured Unit

manufactured oil interceptor

Built On-Site Oil Interceptor

On-Site Oil Interceptors

7.4.4.3.(6):

An on-site constructed interceptor shall be constructed to the requirements of a manufactured interceptor.

7.5.4.2.(2):

Adjacent compartments within an oil interceptor shall be connected to each other by vent opening.

Oil Interceptor

On-Site Oil Interceptor

7.4.4.3.(2):

Except as provided in Sentence (3), oil interceptor shall be provided as follows:

(a)

service stations,

repair shops and

garages or any other establishment where motor vehicles are repaired, lubricated or maintained shall be provided with oil interceptor.

service stations

repair shop

garage

(b)	establishments which use only oily or flammable liquids or have such wastes as a result of an industrial process shall be provided with an engineered oil interceptor.

establishment

7.4.4.3.(3):

Oil interceptor is not required for a drain in a hydraulic elevator pit, parking lot, or a garage used exclusively as a motor vehicle parking area:

elevator pit

parking lot

car wash

garage

7.4.4.3.(5):

Every interceptor shall have sufficient capacity to perform the service for which it is provided.

7.4.4.3.(9):

All grease and oil interceptors shall have an internal flow control and where the head will exceed five feet, a secondary shall be required:

7.4.4.3.(10):

Floor drains that conform to Sentence 7.4.5.1.(3) are not required to be separately trapped and vented, and may be ganged trapped when discharging through an oil interceptor:

If an oil interceptor is used as a trap for ganged trapped floor drains, it should be primed and vented:

7.4.5.5.(1):

Provisions shall be made for maintaining the trap seal of a floor drain or a hub drain by the use of a trap primer, by using the drain as a receptacle for an indirectly connected drinking fountain, or by equally effective means.

7.5.1.1.:

Except as provided in Sentence (2) and (3) and the article 7.5.2.1., every trap shall be vented.

Some authorities require a vent to be installed within 1.5 m of the interceptor outlet. The diameter of the vent is determined by the pipe diameter of the interceptor. If the outlet is 3", the vent would need a minimum diameter of 1 1/2".

7.5.4.2.(1):

Every oil interceptor shall be provided with two vent pipes that

connect to the interceptor at opposite ends,
extend independently to open air,
terminate at least 2 000 mm above ground and at elevations differing by at least 300 mm, and
do not connect to each other or any other vent pipe.

7.5.4.2.(8):

Every vent pipe serving an oil interceptor that is built in location shall be at least 3" size throughout its length.

7.5.4.2.(9):

Every vent pipe serving an oil or grease interceptor that is located outside a building shall be a minimum 3" size.

7.5.4.2.(7):

Where a manufacture of an oil interceptor makes no recommendations with respect to the size of the vent pipe venting an oil interceptor, the interceptor shall be vented at each end with a vent pipe that is not more than one size smaller than the largest connected drainage pipe and not less than 1 1/4" nominal pipe size.

oil interceptor venting