This section is from the book "The Principles And Practice Of Modern House-Construction", by G. Lister Sutcliffe. Also available from Amazon: How Your House Works: A Visual Guide to Understanding & Maintaining Your Home.
The grease from sinks can be removed in two ways - either by adopting an appliance which collects the grease, and from which it has to be removed at frequent intervals by hand (this of course necessitates constant attention, otherwise the system will cause nuisances greater than those sought to be remedied), or by forcing the greasy liquid through the drain before congelation can take place. From a sanitary point of view, the latter method is infinitely to be preferred, though it has to be admitted that the adoption of either method is not strictly in accordance with the provisions of the Model By-laws, as to the space required from the end of the waste-pipe to the gully grating, but one or other of them is absolutely necessary in all houses where much cooking is done especially in the case of hotels, clubs, and restaurants.
Gullies for intercepting the grease are of two types, the one having containers as shown in Fig. 384, in which sand and solids are collected, the grease rising to the top, where it cakes. For moderate-sized houses a large receptacle is required, not less than 2 feet long if the horizontal pattern is adopted, of which Fig. 385 is a type. Opposite the inlet a wall is carried down almost to the bottom of the box, and opposite the outlet is a similar wall, the space between these forming the grease-interceptor. In Adams's pattern (Fig. 386) the movable lid is galvanized and fitted with a sunk grating. The liquid enters through this, then passes down to the bottom of the box, travels slowly across, and rises to the outlet, the silt and sand being deposited and the grease coagulating on the top. For larger houses, hotels, clubs, restaurants, Ac, a much larger collecting-box is necessary - not less than 3 feet long. The construction of these is slightly varied by the introdurtion of a mid-feather w, as shown in Fig. 387, which illustrates Hellyer's "extra-large" greaae-trap, which has a vent-pipe v on the inlet-arm and an access-hole for the drain at I on the outlet-arm, and is covered with a holed Hag in which an air-tight iron cover is inserted. Fig. 388 shows the " Eclipse" grease-trap, and needs little explanation; the greasy water from the sink, after leaving the inlet-pipe, passes to the bottom and then slowly along the entire length of the trap; the greasy particles, chilled by the large body of standing water in the trap, rise and remain in the centre chamber undisturbed by the water flowing below.
Fig 384 - "Loco " Grease- trap with Retainer.
Fig. 386 - Grease- trap for Moderate-sized House.
Fig. 386 - Adam's Grease-trap.
Some makers adopt a deep vertical type of greaae-trap, as shown in Fig. 389, which illustrates Bolding's "Simplex" grease-trap. The principle is the same as in the horizontal ones, the direction of the flow being downwards instead of horizontal.
Grease-traps are sometimes made in cast-iron instead of stoneware, and Mr. Hellyer has patterns of movable ones which are coupled to the waste-pipe by a screw-union; and there are also others which can be fitted on the floor under the sinks.
For small houses self-cleansing grease-gullies are much to be preferred, as there is not an excessive amount of grease requiring extra force to break it up. The gully shown in Fig. 390 is known as "Le Rossignol's Patent Self-cleansing Grease-gully", and was designed specially for the purpose. It should always be fixed with the inlet a taking the sink-waste, and the side inlet taking the bath or lavatory waste. The angle at which the inlet a is constructed causes the water to rush over the lip B (where it has a fall of three inches to the level of the water in the trap) with such an impetus that it ensures the effectual cleansing of the trap, breaking up any fat floating on the top of the water, and carrying it into the drain. Additional flushing through the same inlet may be obtained from the hot-water tap, which in most houses is to be found over the sink. The trapping lip c, being at the same angle as the inlet a, offers the minimum of resistance to the scouring out of the grease. The gully should not be used as a yard gully for surface-water, and should preferably be fixed half an inch above the ground-level to prevent the entrance of gravel or grit, which might impede the scouring out of the grease.
Fig 387 - Hellyer's Stoneware Graese-gully,for large Houses, Hotels,&c.
Fig. 388 - "Eclipse" Grease -trap.
Fig. 389 - Bolding's "Simplex" Grease -trap.
SECTION CROSS SECTION Fig. 390 - Le Rossignol's Self-cleansing Greate-gullr.
In large establishments where there is a considerable quantity of grease, special means must be taken to despatch the grease into the drains before it coagulates. To do this successfully special gullies with provision for flushing have been introduced. Hot grease on entering the trap comes into contact with the cold water contained therein, solidifies, and rises to the surface; a powerful cold-water flush is introduced by means of an automatic system, and thoroughly cleanses the trap and carries the grease into the drain. Fig. 391 shows Hellyer's pattern, which is fixed in a small brick chamber. Just enough water is retained in the trap to congeal the grease; the flush from the automatic flushing tank ft enters the trap at the back, a portion of the flush passing through a flushing rim with a jet opposite the outlet for breaking up the congealed head into small pieces and floating them through the drain, the remainder of the flush being conducted downwards by a separate water-way to the bottom of the trap for scouring out solid matter. A 20-gallon flushing tank is used, and where a bead of from 4 feet to 7 feet can be obtained the Mush is 3-inch bore, butut where the head is less, 4-iuch. The flushing tank may be fixed in any convenient position within 20 feet or 30 feet, so long as the necessary head is obtained, and by a little contrivance the waste-water from baths may be utilized for flushing purposes, the tank being placed outside. When this position is adopted, special means must be taken to prevent freezing, and to secure its efficient working during the winter; it should also be covered over to keep out leaves and litter. Fig. 392 shows a very simple flushing tank manufactured by Bowea- Scott & Western. Fig. 393 shows Winser's patent reversible flushing-rim grease-gully. It is made in two pieces. The trap can be turned in any direction to suit the drain; the upper portion can also be turned to suit the connection from the automatic Hushing tank. This meets the now usually adopted plan of concentrating the wastes and rain-water pipes to a central gully, which in some cases also receives the surface-water. Fig. 394 is the same trap, but has an extra raising-piece to receive the various inlets; this allows the three pieces - viz., the connection for the drain, the connection from the tank, and the connection for the various inlets, - to be turned in any direction independently of each other. This is perhaps a more convenient form, but requires an extra depth of drain. The tops are supplied with four 2-inch holes or with one 2-inch or three 4-inch holes. The outgoes of the traps are made both 4-inch and 6-inch, the 6-inch being recommended as giving more freedom to the flow of the water
Fig. 391 - Hellyer's Flushing Graese-Trap.
Fig .301 -Bowee-Scott & Western's Automatic Flushing Grease-trap.
Fig. 396 - Winser's Flushing -rim Grease -gully.
Fig. 394 - Winser'sFlushing -rim Grease-gully with Raising- piece.