A Mem. Am. Soc. C. E., New York, writes: "In your opinion, is a grease trap an absolute necessity in a well-planned drainage system for a country house, and if so, why not equally necessary in a city house, where the horizontal run from the kitchen sink to the sewer is 80 or 90 feet? Most country houses have a grease trap close to the house. Granted the necessity of the grease trap, why should this be nearer the house than the sewer in the city? Granted the necessity of the grease trap, what is the extreme distance from the house at which it may be placed, and sewer properly ? Is it not as objectionable as a cesspool, and, with subsoil irrigation to avoid the latter, do we remove the danger it the grease trap remains? Do you know of any case where flush tanks have been used without grease traps or settling basins, the house sewage draining to the flush tanks direct, and being disposed of immediately ? "

[The necessity for using a grease trap depends on several things: First, the probable amount of greasy water disposed of in a kitchen; second, the distance the greasy water must flow to reach the sewer or cesspool; and third, the length of soil pipe orearthern drain that may be buried in the ground.

A grease trap, like other traps used in drainage, must be considered as a compromise; in other words, it is used to prevent a greater evil. A small family, keeping one or two servants, may safely dispense with one, but when a number of servants are employed, and much cooking is done, and in a country house, where the waste water must pass through pipes buried in the ground where the greasy water will be rapidly chilled, we should advise the use of a grease trap.

In a city house, as in New York, for instance, the average distance of the sewer from the kitchen sink is about 90 feet, but for 60 feet of this distance the hot greasy water flows through an exposed and accessible iron pipe in a cellar which, during the winter months, when the house is occupied, is warm, so that the water is not chilled, and grease precipitated until it reaches the sewer. Besides, in properly planned work, cleanouts are provided for the removal of obstructions. If a grease trap is placed within a house, the grease should be removed from it every few days and before it becomes putrid, otherwise cleaning it is a very offensive operation. A grease trap should be located nearer the house than the sewer, and as near the source of the grease as circumstances will permit, taking into account the offensive smells when grease is removed. In country houses they are usually located in a vault just outside the house.

From the point of view of the householder, if all the grease could reach the sewer no grease trap would be needed. On the other hand, a town provided with small pipe sewers is liable to find trouble from stoppages from this cause. We believe that Mr. E. W. Bowditch, of Boston, has recommended towns where he has designed a small pipe sewer systern, that they require grease traps when houses are within 50 feet of sewers, but when the private drain is more than 50 feet, to leave it optional, relying on the grease to precipitate in the drain and not reach the sewer. A grease trap is not as objectionable as a cesspool, since it is not supposed to receive anything but greasy water, and is intended to be frequently cleaned.

We do not recall any place where house sewage is delivered to a flush tank and periodically discharged from it into a sewer, and should consider such use of a flush tank objectionable. This of course does not apply to disposal by subsurface irrigation, where a settling basin and flush tank are required]