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Sizing For Grease Interceptor sizing, please reference the Sizing Guide or the Plumbing Drainage Institute Standard PDI-G 101.Without a properly sized flow control,the flow through the interceptor may exceed the rating of the unit,causing lower efficiencies and allowing grease to pass through the interceptor into the downstream piping. Be careful that you do not confuse liquid capacity and flow capacity. Liquid capacity is rated litres or gallons while flow capacity is rated in gpm (gallons per minute)or Ipm(litres per minute). If sizing indicates that a larger Grease Interceptor is required, you maybe able to compromise to a smaller unit by adopting to a 2 minute drain down time in your sizing calculation. Although the smaller unit will be less expensive, the grease capacity of a smaller unit will dictate the cleaning frequency required. Mop Sink Sizing Guide Floor Drains &Floor Sinks Size LPS US/GPM Take the volume of water produced by the number 2" 84 22 3" 142 37.5 of hose bibs(ie 1.5-2.0 gpm per 3/4"faucet) 4" 170 45 Table A-Procedure for Sizing Grease Interceptors STEP FORMULA EXAMPLE 1 Determine cubic content of fixture A sink 24"long by 20"wide by 12"deep. by multiplying length x width x depth Cubic content:24 x 20 x 12=5,760 cubic inches (61.0 x 50.8 x 30.48 cm') Determine capacity in gallons. Contents in gallons: 2 1 gallon=231 cubic inches 5,760/231 =24.9 gallons (94,451.42/1,000=94.45 litres Determine actual drainage load. Actual drainage load: 3 The fixture is normally filled to approximately 75%of capacity with water .75 x 24.9=18.7 gallons as the items being washed displace about 25%of the total fixture content. (0.75 x 94.45=70.84 litres) Actual drainage load=75%of fixture capacity Determine flow rate and drainage period. Calculate flow rate for one minute drainage period: In general,good practice dictates a one minute drainage period; 18.7/1 =18.7 g.p.m.flow rate however,where conditions permit,a two minute drainage period 4 is acceptable.Drainage period is defined as the actual time (70.84/1 min.=70.84 I.p.m. required to completely drain the fixture. Calculate flow rate for two minute drainage period: Flow rate=Actual Drainage Load 18.7/2=9.4 g.p.m.flow rate Drainage Period (70.84/2 min.=35.42 I.p.m.) Select Interceptor. For a one minute drainage period: 18.7 g.p.m.(70.84 I.p.m.)flow rate=20 g.p.m.G.I. 5 From Table B select the interceptor with a flow rating at least equal to the calculated flow rate.When the calculated flow rate For a two minute drainage period: falls between two sizes,select the larger of the two interceptors. 9.4 g.p.m.(35.42 I.p.m.)flow rate=10 g.p.m.G.I. Table B-Procedure for Sizing Grease Interceptors PDI Size Symbol 4 7 10 15 20 25 35 50 Flow Rate US Gallons per Minute(GPM) 4 7 10 15 20 25 35 50 Flow Rate Liters per Second(LPS) .25 .44 .63 .95 1.26 1.58 2.20 3.16 Grease Capacity Pounds(Lbs) 8 14 20 30 40 50 70 100 Grease Capacity Kilograms(Kgs) 3.63 6.35 9.07 13.61 18.14 22.68 31.75 45.36 Sampling Access Some municipalities require a sampling port to monitor effluent quality. If the unit is on the floor, or semi-recessed into the floor,a cleanout tee can be installed downstream of the Grease Interceptor. If the unit is installed in the floor,a backwater with its flapper removed, makes an effective collection port. Venting Grease Interceptors must have a vented waste,sized in accordance with local code requirements for venting interceptors to retain a water seal and prevent siphoning. Most codes dictate that two vents be installed,one upstream and one downstream of the grease interceptor.The upstream vent must not be placed between the air intake and the grease interceptor. 6