Hot Water Heating. 35 



nary sized boiler. Connect this barrel by means of an 

 inch pipe with your return just before it enters the 

 boiler, and all waste of water in the circulation can 

 be supplied from this point. Should the flow at its 

 highest point not be supplied with a stand pipe, it is 

 best to tap the flow as it leaves the boiler, inserting an 

 inch pipe and carrying it over and just into the top of 

 the expansion tank. This will not only allow air to 

 escape, but should the fires be crowded so that steam 

 is generated, it can escape at this point and what is 

 termed '"kicking" pipes will be avoided. As to the 

 height of this tank, the bottom of it should always be 

 higher than the highest part of any of the pipes. 



CHAPTER VI. 

 THE DOWN HILL SYSTEM. 



The second system of hot water heating is what is 

 called the "down hill system," and difiers from the one 

 just described in that the water is raised to the highest 

 point at once, and from that point gradually falls until 

 it reaches the boiler again. This gives an opportunity 

 for overhead heating, which for some crops is beneficial, 

 while to others it is detrimental. 



To lay these pipes, commence with the flow, raising 

 it perpendicularly from the boiler, to such a height 

 as will permit you to carry the main from which your 



