Estimate all pipes and fittings the same as for plumbing. Sum up all standard radiators, and the price per square foot of radiation. Figure special radiators separately. Itemize all valves, air vents, hangers, etc. Estimate on pipe coverings by linear foot. Estimate sheet-metal, indirect-radiator casings in pounds. Estimate sheet-metal flues and smoke pipes by the linear foot; but estimate elbows and dampers separately. Estimate register boxes, registers, and borders separately. Make separate items of expansion tanks, hot-water damper regulators, and furnace regulators. Figure heaters, steam boilers, and furnaces from manufacturers’ catalogs. In estimating on heating by furnace, the average cost of labor is about one-third that of materials. For steam and hot-water heating, the ratio is about one-fifth. The cost of a hot-air installation is approximately 6 per cent. of the cost of the building; for steam heating, 8 per cent.; and for hot-water heating, 10 per cent. PLUMBING AND GAS-FITTING PLUMBING =96.= An approximate figure for the cost of =plumbing= is 10 per cent. of the cost of the building. This figure is for good materials and labor, and of course is subject to considerable variation. The cost of labor alone will average about one-fourth the cost of the materials. =97. Drainage System.=—In making estimates for the =drainage system=, measure all horizontal pipes from the plans and all vertical pipes from the sectional drawings. Commence at the sewer outlet and measure the main-sewer line forwards into the building; then measure the horizontal branches. Measure the vertical, soil, waste, and vent stacks to their terminations above the roof, and waste-pipe branches to the fixtures on the several floors. Itemize the several pipes in the different kinds and classes. Estimate all earthen pipe by the linear foot, allowing for Portland cement in the joints. Estimate all cast-iron pipe by the linear foot, allowing for each joint ¾ pound of lead for every inch in diameter of the pipe. Estimate wrought pipe by the linear foot, inclusive of couplings. Estimate brass, copper, and lead pipe by the pound. Estimate all traps, bends, branches, increasers, reducers, and other fittings separately, except such special brass fixtures, traps, and connections as are included in the cost of the fixtures. Do not figure lead bends that are smaller than 2 inches. Estimate on brass ferrule connections at all points where lead pipe joins iron pipe. Estimate on all solder joints (wiped), allowing 1 pound of solder for every inch inside diameter of the pipe. =98. Water-Supply System.=—For water supplied from street mains, allow for permits, corporation tapping, and curb box. Measure the service pipe from street main to cellar, and allow for a stop and waste cock inside the cellar wall. Measure all horizontal distributing pipes from the plan views of the building and all vertical distributing pipes from the sectional drawings.