Page:Steam heating and ventilation (IA steamheatingvent00monrrich).pdf/36

 a heating system, it can be made to maintain what is now called a dry return. This is in some cases valuable, as it obviates the necessity of considering the water-line, as before mentioned, in placing radiators in basements. Vacuum pumps used in this way are especially valuable in cases where return water is to be brought back from a heating system at some distance from the source of steam supply.