Much information has been given from time to time of the best way to run the circulating-pipes between a water-back and boiler; but the proper position in the boiler for the pipe-connections does not seem to be understood, if I may judge from a boiler recently received from a large manufacturer, in which the couplings were so placed that only about one-half the capacity of the boiler would be available for use.

The boiler was to rest horizontally - a position in which many boilers are now set, and the diagrams, Figures 97, 98, 99, show the pipe-connections. D, inlet for cold water, with tube running into boiler; B, for hot water to pass out; A and C, upper and lower circulating connections.

A moment's thought will show that water below C will not heat, and that the water above B cannot be drawn off. The capacity of the boiler is therefore only that portion between the horizontal planes passing through C and B, Figure 97, or very little over one-half the whole boiler. The proper position for couplings to horizontal boilers are shown in Figures 98 and 99, in which D represents the cold in pipe; B the hot out pipe; A, upper circulation; C, lower circulation. Now, a moment's thought will show that the water below C will not heat, and that the hot water above B cannot be drawn off. The capacity of the boiler is therefore only the part between horizontal planes passing through C and B, in the case we allude to, just about one-half the whole boiler. Or, where the pipes can be conveniently connected at the top side of boiler.

In a vertical boiler we have never seen the couplings improperly placed. Care, of course, must be taken to have the inside tube upon the coldwater supply to boiler, but in horizontal boilers care is not always taken to observe the following rules, applicable alike to vertical and horizontal boilers: First - Cold water should be delivered into the boiler at a point near its bottom. To prevent the boiler being emptied through this cold supply-pipe it is best to have the coupling near the top of boiler, and carry a pipe from it inside the boiler to near the bottom.

Figure 97.

Figure 98.

Figure 99.

Figure 100.

Second - The lower circulating-pipe should connect at or very near the bottom of the boiler, so that all the water in the boiler may be heated. The position of the upper circulating coupling is not material.

Third - The outlet-pipe for hot water should be at the top of the boiler, so that all the hot water may be drawn off.

Fourth - The inlet and outlet pipes should not be too near together, lest the rapid flow, when hot water is drawn, establish a current between them, and so fail to draw the hot water from the boiler.

Where a boiler is too small and it is desired to add another boiler, instead of throwing out the old one and replacing it with a single large one, I have coupled them as shown in Figure 100. Both boilers heat alike, and are drawn off together.