This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
The steam main should be connected to the rear nozzle, if a tubular boiler is used, as the boiling of the water is less violent at this point and dryer steam will be obtained. The shut-off valve should be placed in such a position that pockets for the accumulation of condensation will be avoided. Fig. 66 shows a good position for the valve.
The return connection is made through the blow-off pipe and should be arranged so that the boiler can be blown off without draining the returns. A check valve should be placed in the main return and a plug cock in the blow-off pipe. Fig. 67 shows in plan a good arrangement for these connections.