Grease traps should be used to intercept the grease from all kitchen sinks in cities that have installed systems of sewerage from which storm water is excluded. Under such conditions, the sewers are so small and so poorly flushed that great liability would exist of partial or complete stoppage from the grease if grease traps are omitted. When a city has installed a combined system of sewer and storm water drains, grease traps may be omitted if the kitchen sink is not over fifty feet from the street sewer and the main house drain runs through the cellar exposed to the heat of a furnace. However, when the sink is over fifty feet from the street sewer, or when the main house drain is buried in the earth, so grease would be likely to chill before it reached the street sewer, grease traps should be used. Also they should in every case be used in all large institutions, boarding houses, hotels and bake shops or other buildings where large quantities of grease are liable to find their way into the drainage system.

Fig. 43

Fig. 44