In marking plumbing apparatus, such as pumps, tanks, filters, meters, heaters and manifolds, on plans, the chief requirement is to locate them in their right places and see that they are drawn to scale so that they will show the proportionate spaces they will occupy in the building. Square, or rectangular, suction or house tanks can be indicated by means of a rectangle or square, drawn to scale, and showing the connections to the tank. The method of indicating a suction tank, supported on I-beams, is shown in Fig. 24. The four lines bounding the rectangle merely define the size of the tank, and the name, dimensions and other data may be marked within it or alongside. In detailing a tank and its connections, of course, a more complete drawing would be necessary. A conventional plan drawing of a circular house tank is shown in Fig. 25. It is merely indicated in its proportionate size by two concentric circles and is shown resting on two I-beams, which in turn are supported by the two walls of the building which form an angle at that point. Meters are generally shown as indicated in Fig. 26 and with a bi-pass around them. If, where the work is to be installed, the water authorities will not permit a bi-pass around the meter, a second meter is put in the bi-pass in all large buildings, and the bi-pass omitted entirely in others. House filters are shown as a circle or double concentric circle, fitted up with a bi-pass. If a circle were substituted for the symbol of a meter in Fig. 26 the illustration would pass very well for a filter connection. The method of indicating a water heater, in plan, is shown in Fig. 27. Usually this symbol is drawn alongside of a large circle which represents the hot-water tank, and pipes are shown connecting the two parts of the heating outfit together. In detail drawings, the heater is shown, in elevation, as illustrated in Fig. 28. If a hot-water tank which is to be heated by a water heater, is intended to be suspended from the floor beams in a horizontal position, it may be indicated as shown in Fig. 29, but without the steam coil which is represented by dotted lines. If, on the other hand, the water is to be heated by means of steam circulating through a steam coil, the coil is indicated by means of dotted lines, as shown in the illustration. In either case bands may be shown supporting the tank from the overhead beams, or details may be made showing the form of hangers or rests to be used. Pumps may be shown conventionally in plan, as in Fig. 30, and in elevation as in Fig. 31. The symbols illustrated in the fore-going paragraphs need not be closely followed, but any designs or symbols which will represent the apparatus they stand for, with the least expenditure of labor, consistant with good work, will answer. Nevertheless, in the interest of uniformity and simplicity, it will be found desirable in practice to follow the general outline of the symbols indicated. They have long been tried in the drafting room, and are known to be simple, practicable and easy to make.