In cottages with no bath and with small culinary requirements, a 30-gallon reservoir is sufficient. Not less than 40 gallons should be employed for a bathroom job. The capacity of the average stove heater is even too great for 40 gallons' storage unless there is liberal use of hot water; but where gas is used and the water heating inde pendent of the cooking heat, as it generally is, the temperature can be regulated to suit. A storage capacity of 52 gallons or more is usual for large residences.
Gas Heaters. There are gas heaters provided with thermo static or pressure mechanism by which the hot service is taken care of automatically. The latter of these are simply connected in the line in a convenient place. In one type, the appearance and con struction of which is shown in Fig. 89, simply opening any hot-water faucet reduces the pressure, and the gas is thereby turned on. A pilot light ignites it, and the supply is heated as fast as it passes through the copper coils of the heater. No storage capacity is required by this form. In another form, shown in Fig. 90, the heater is controlled by a thermo static valve projecting into the regular reservoir used with it. When the water in the reservoir is heated to the desired temperature, the gas supply is reduced or cut off. A section of this heater is shown in Fig. 91. It consists of a chamber surrounded by an outer jacket with an air-space between. Circulation pipes, through which the water passes, are hung in the inner chamber, just above a powerful gas-burner placed at the bottom of the heater. Drawing water from
the hot faucets lowers the temperature in the reservoir through the cooling influence of the incoming water, and the thermostatic prin ciple is again made to serve in opening the gas-valve until the water is heated to the desired temperature.
There are other arrangements consisting essentially of an encased copper coil, above a gas-burner, connected to a standard reservoir at top and bottom. In these, the gas is turned on and regu lated by hand as nearly as possible to suit the needs.
Instantaneous water-heaters, operated by gas or gasoline, and placed in prox imity to the fixtures served, as shown in Fig. 92, so as to deliver the heated water directly, are in general use where local conditions favor them. These have no storage capacity. A sectional view of Fig. 92 is shown in Fig. 93, in which A is the gas-valve; B, the water-valve; D, the pilot light; FF, the burners; I, a conical heating ring; J, a disc to retard and spread the rising heat; K, a perforated copper screen; and L, a revolving water distributer. In this heater, the water is exposed directly to the heated air and gases, in addition to its passing over the heated surface of the ring I.
Other heaters of this class offer admirable means for the water to take up the heat generated by the gas. All of these special means of beating water—especially those not conforming to the plumber's regular routine—are best understood and judged by a close study of the literature supplied by the makers.