The lead roughing for a toilet room is estimated by taking off all the quantities, such as lead pipe, bends, traps, ferrules, solder nipples and solder required for the work. To this, of course, would be added the cost of labor, operating expenses, profit, etc., but these would be made up separately and not confused with the items of materials. For instance, in taking off quantities, instead of allowing so much for that work and adding at the same time the percentage for operating expenses and profit, the materials alone are taken off first, then the labor for the entire installation is calculated when there is nothing else to keep in mind, after which, when the entire list of quantities is completed and the cost ascertained, the items of profit and expense are added. In the example illustrated in Fig. 4 the estimator must bear in mind that the pipes are not all on one plane, as indicated, but that the fixture centers are located on an average about fourteen inches from the wall where the pipes are concealed, and allowance of that length of pipe must be made for each back vent or waste pipe where it crosses under the floor to intersect the main waste pipe. Keeping this in mind, the length of the different sizes of pipe can be scaled and the amounts jotted down. Having the amount of lead pipe, the number and sizes of traps, bends and ferrules should be noted. The oakum and lead for calking the ferrules will be allowed for in the estimate of the soil pipe, so that of all the materials for the lead roughing of this layout only the solder remains to be calculated. A common practice among plumbers is to allow one pound of solder for each wiped joint; but that method, at best, is but a system of guesswork. If the joints to be wiped are all small and the plumber who installs the work makes short, skimpy joints, an allowance of one pound might be entirely too much, while if the pipes are all large and the plumber wipes long heavy joints the allowance will be entirely too small. The best way is for the careful estimator to familiarize himself with the size and weight of joints wiped by the employees of his shop and either by measurement or weighing ascertain the average weight of joints on each size of pipe, then, making due allowance for solder that is lost in wiping or stolen from the job, a fair idea of the weight of solder to allow per joint can be formed. This is not so trifling and unimportant as it might seem, for the difference in amounts of solder used in different cities is considerable. For instance, around St. Paul, Minneapolis, Duluth and West Superior the average length of joints on 5/8 lead pipe used to be about three inches, while at the same time in Chicago the same size joints did not average over 1 inch in length. It stands to reason, then, that if the 3-inch joint took only one pound of solder, the 1-inch joint would take but one-third of that quantity, and should be so calculated on. To give some idea of the carelessness of the pound-per-joint method of estimating, and at the same time show how to approximate the amount of solder used in a joint, reference is had to Fig. 5. This shows a section of 4-inch pipe cut in two lengthwise through a joint.

Fig. 4.

The solder in this joint is assumed to be § of an inch thick, and 2 1/2 inches long.

To find, then, the approximate cubical contents of the solder it is necessary to find the length of the joint if rolled out into a straight line. The inside diameter of the pipe is 4 inches, the pipe 1/8-inch thick and the thickness of the solder 3/8-inch, so that the distance, (a), would be equal to 4+2/8+3/8=4 5/8 inches. This represents the diameter of the ring of solder forming the joint, and as the circumference of a circle is 3.1416 times the diameter, the length of the solder joint is 4 5/8 = 4.625 x 3.1416 = 14.52 inches. The joint extends 2 1/2 inches along the pipe and is 3/8-inch thick, but it tapers from end to center, so that in the average joint, if spread uniformly over the entire surface, the solder would be, perhaps, about 1/4-inch thick. If, then, the length of the joint be multiplied by the width and thickness the entire cubical contents of the solder in inches will be found. Thus, in this case, 14.52 x 2.5 x .25 = 9 cubic inches of solder on a 4-inch joint.

Fig. 5.

Solder, such as is used for wiping weighs approximately .352 pound per square inch so that the solder for a 4-inch joint would weigh 9 x .352 = 3.168 pounds. It will thus be seen that allowing one pound of solder for a 4-inch joint entails a loss of over two pounds on each joint wiped not counting the solder tossed away in the process of wiping and never recovered. In view of this fact, and the further one that according to the same calculation a 2-inch pipe requires 1 3/4 pounds of solder it may be well to again emphasize the necessity for determining the actual amount of solder required for joints of various sizes and not depending on the pound-per-joint method which does not give even approximate results.

In the absence of exact data as to the quantity of solder required for wiping joints, an empirical rule, which will be found perfectly safe even allowing for loss due to flipping pieces of soft metal from the pipe, is to allow for each large joint one pound of soider for each inch in diameter of the pipe, and for pipes smaller than 1-inch in diameter, one pound of solder per joint. According to this rule the solder required for the work shown in Fig. 4 would be ascertained as follows:

Lead pipe is sold by the pound, so that once the quantity of the various sizes of pipe is ascertained it can be reduced to pounds by multiplying the lengths of the various sizes of pipe by the weights per foot. The weights of lead pipe of various grades can be found in Table XV.