Formerly, 4-inch cast iron pipe was used extensively and rust joints were in common use. Wrought iron pipe is now generally employed, and it is always threaded—an advantage that makes installation more rapid and provides joints which are not so likely to leak. Most frequently 1 1/2 and 2-inch pipe is used for the coils in hot water heating and 1 1/4 - inch pipe for steam heating, connecting with mains of proper size. Whatever the system, the pipe should be placed with the greatest care, observing the principles of the method of heating to be used.
The boiler should be of ample capacity to maintain proper temperatures; forcing a boiler means a waste of fuel, and the boiler itself will not last so long. There are several types of boilers on the market. The most important point to consider in selecting a boiler is to see that the construction is of such a type that the greatest heat will be realized from the fuel consumed. The flames should strike the sections of the boiler at right angles, and the connection with the smoke pipe should not be too direct. Sectional and tubular boilers are in most common use in greenhouse heating.
In every greenhouse establishment there is a great deal of work to be done in the way of seed sowing, transplanting, potting and preparing crops for market. Nothing is more important than a commodious room where all the work can be done in perfect comfort. This room should be well lighted and properly heated and ventilated. Tables of the right height are necessary, and a small room for tools will be found very convenient.