44 



THE CONSTRUCTION OF THE FORCING-HOUSE. 



them, should be underneath the bed. The steam or hot 

 water is carried into the house by means of one or two 

 pipes, called risers when steam is used, and flow-pipes 

 when water is used, and is returned to the heater through 

 from two to six times as many returns. The risers or flows 

 are usually carried into the house overhead, and the returns 

 are carried underneath the benches, along the walls, or the 

 sides of the walks. Aside from the greater number of pipes 

 required in water heating, there is little difference in the 

 methods of piping for the two systems. The highest point 

 in the steam riser should be directly over the heater, or, 

 when this is not practicable, it should be at the near end of 

 the house or the system, and the riser should gradually fall 

 from this point to the far end of the house. This gives a 

 down-hill system. It is generally considered that the 

 highest point in the water flow-pipe should be at the far end 

 of the house or system. This is an up-hill system. Flow- 

 pipes should not be less than 2 inches in diameter for runs 

 of 60 ft., while steam may be carried in a r>-inch riser 

 under similar circumstances. In water runs of this length, 

 there should be two risers for houses 16 to 20 feet wide, 

 particulary if warm plants are to be grown. 



The amount of pipe required for special cases may be 

 determined by examining some of the plans and illustra- 

 tions. Fig. i illustrates two methods of piping. It may be 

 piped by running a water flow pipe underneath the bench 

 on either side and carrying back two returns under each 

 flow. This type of heating is not common. In such cases, 

 it would no doubt be necessary to keep the space under 

 the benches cpen next the walk in order to heat the house. 

 A commoner method is to carry a riser or flow overhead at 

 X, and to bring back six returns from it. In Fig. 2, a 2-inch 

 steam riser is carried overhead in the center, and it breaks 

 into seven i^-inch risers underneath the benches. There is 

 a similar arrangement in Fig. 3. These two houses would 

 grow tomatoes in New York state. In Fig. 4, two 3-inch 

 water flows near the peak supply six i^-inch returns under 



