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 inch pumps. These deliver the return water through the closed heater into the boilers. There are three pumps used for this pur- pose, and so connected that any one can be used on the governors separately or together, and any one can be used to pump cold water through the heater. The feed pipe has a by-pass around the heater, to be used when the heater is being cleaned.

Return pipes should be given as much pitch as possible except where they are below the water-line of the system. In running these below basement floors they should be put in trenches, prefer- ably of brick or concrete, and with movable covers. If there is danger of water underground the trenches must be arranged so that they can be kept dry, and no better trench can be made than one of good concrete.

Pipe coverings. All the piping connections should, as far as. possible, be covered with some kind of non-conducting pipe cov- ering, of which there are innumerable varieties made. In some cases risers and other pipes are left uncovered so as to utilize the- heating effect, but the disadvantage of this is that heat is given out from such pipes whether it is wanted or not, and it is much better practice to cover the risers and depend on the radiators, for heating. One of the greatest sources of fuel waste is found in uncovered mains in basements of buildings where heat is noth- ing but an inconvenience, and in order to dispel it in moderate weather windows are opened, which greatly increase the wasteful condensation. A good pipe covering will save from 65 to 80 per cent, of the heat which would ordinarily be wasted from the pipes. Coverings of which 85 per cent, is carbonate of magnesia, certain molded forms of pure asbestos fiber, and molded forms of mineral wool are the best kinds of protection for steam pipes to reduce condensation. Some coverings which show very good results when new, deteriorate rapidly, due to the charring effect of the pipes and to disintegration.

Pipes and flues for indirect radiators. "We come now to the con- sideration of certain details of construction which are especially requisite in indirect heating. In this class of steam heating the piping connections are subject to much the same rules for run- ning pipes as those for direct radiators, but indirects are almost invariably located in the basement of buildings and the pipes run- ning to them are horizontal. Furthermore, the condensation per square foot of indirect radiator is from 25 to 50 per cent, more