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Grease trap

Calculates the nominal size of the fat separator needed for the current plant.

Grease trap

Input Result
Maximum flow rate Qs=
Temperature factor ft=
Density factor fd=
Cleansing factor fr=
Nominell size NS=
Sludge separation volume VS=

Flow rate alternative 1

Type of kitchen equipment Max
Number Aggregated
qi (l/s) n (pcs) Zi (l/s)
Cooking pot 25mm outlet
Cooking pot 50mm outlet
Tilting cooking pot 70mm outlet
Tilting cooking pot 100mm outlet
Rinse box 40mm with siphon
Rinse box 50mm with siphon
Rinse box 40mm without siphon
Rinse box 50mm without siphon
Tilting griddle
Fixed griddle
High pressure cleaning or steam cleaning
Vegetable wash
Drain point DN15
Drain point DN20
Drain point DN25
Aggregated maximum flow

Flow rate alternative 2

Input Result
Peak flow coeff F=
Means run time t= h
Meals m= pcs/day
Maximum flow QS=


Grease trap

Grease trap is used to take care of the fat that is flushed down the drain before operating it gets out into the public grid. The reason for doing this is that the fat can clog the pipe network and create clots. The demands on the need varies between municipalities, but in general, the requirement is that there should be a grease trap on virtually all commercial kitchens serving hot food. The toilets and the like should never be connected to a grease trap.

Temperature factor

At higher temperatures of sewage effectively reduces ethylene on grease trap this fact is compensated with temperature factor according to table below.

Temperature of the wastewater at the inlet Temperature factor
<= 60˚C 1,0
> 60˚C 1,3

Density factor

Density factor is the factor that handle the density of the fat that is flushed down the drain. If the density is unknown, factor set to 1.0. On the other hand the density known, the graph below used to obtain the correct factor. Exceeds the density of fat is 0.94 g / cm 3 is the factor to 1.5.

Nedan visas densiteten på ett antal vanligt förekommande fetter.

Grease/oil Density at 20˚C in g/cm3
Animal grease0,85 - 0,94
Butter grease 0,91
Coconut butter 0,89 - 0,94
Castor oil 0,95 - 0,97
Coconut oil 0,92 - 0,93
Corn oil 0,92
Fish oil 0,89 - 0,94
Linseed oil 0,93 - 0,94
Olive oil 0,91
Palm oil 0,91 - 0,92
Rapeseed oil 0,91 - 0,92
Sesame oil 0,92
Vegetable oil 0,95 - 0,97

Cleansing factor

Cleaning factor takes into account how much detergent and fabric softener used in washing. The type of detergent and fabric softener should be used sparingly and should be chosen so the separating effect on the fat reduces the effectiveness of the grease trap.

Use of detergent and rinse aid Cleaning coeff
Never used 1,0
Rarely used 1,3
Special case ie hospital 1,5

Nominal size

Nominal size is the calculated value used to select an appropriate size of a grease trap.

Sludge separation Volume

It contemplates the size of the chamber of the grease trap handling the sludge that comes with the wastewater.

Mean wastewater volume

Refers to the average value of the waste water that reaches the grease trap per day in liters.

The maximum flow rate

is the main flow from the actual plant that reaches the grease trap.

Drain point

Are there two or more drain lines that are not connected to any device, these must also be added to the calculations.

Medium Run

Refers to how many hours per day that the plant is running at average.

Peak flow coefficient

This is a factor which depends on the type of activities carried out in the actual plant.


Refers to the number of meals served per day plant.


Nominal size: Nominell storlek
Flow alternative 1: Flödeshastighet alt 1
Flow alternative 2: Flödeshastighet alt 2
Mean wastewater volume:: Medelavloppsvattenvolym