“The hot water system is said to be cheaper,” replied Dorothy.
“Why are there so many pipes?” asked Ethel Brown, looking with a puzzled air at the collection before her.
“Hear me lecture on heating!” laughed Dorothy; “but I did study it all out with Mother, so I think I’m telling you the truth about it. There have to be two sets of pipes, one to take the hot water to the radiators and the other to bring it back after it has cooled.”
“There seem to be big pipes and small ones.”
“Mains and branch pipes they call them. The man who put these in said this house was especially well arranged for piping because it wouldn’t take any more pressure to force the water into one radiator than another. He says there’s going to be a good even heat all over everywhere.”
“There isn’t a lot of difference between radiators for steam and those for hot water, is there?” asked Ethel Blue.
“No, you have to put something with water in it on top of both kinds to make the air of the room moist. Here you have to open the air valve yourself and let out the air that accumulates in the radiator. In the steam ones they are automatically worked by steam.”
“There can’t be much air in the hot water radiator, I should think,” said Margaret thoughtfully.
“There isn’t. You only have to open the valve two or three times in the course of the winter. The biggest difference is that the hot water system has to have an expansion tank.”
“What’s that?”