The preservation of old estimates and complete lists of stock used will often allow the estimator to refer to them and get a line on work of similar nature which he may be figuring. Galvanized vent fittings should be estimated in detail as far as possible, just as soil-pipe fittings are estimated.
Stop cocks, valves, sill cocks, solder nipples, and unions should also be estimated as nearly in detail as possible, as an offhand estimate of material that represents so much cost as these items is not a safe thing.
Gas piping often enters into the plumbing contract. It is sometimes safe on new work to approximate the cost of the gas piping at so much per outlet. If this can be done it saves considerable labor in figuring out the cost of different sizes to be used, fittings, and labor.
Reference to previous work of similar nature is of much help in this connection. Estimating at so much per outlet is not a safe method on old work, that is, where gas piping is to be installed in an old house. Many plumbers are inclined to estimate old work in this way, however, and often suffer loss thereby.
Water, gas, and range connections are not generally considered a part of the general plumbing contract in many sections, but in other sections must be included.
There is little to be said on the matter of estimating fixtures and their trimmings. Sizes and list prices may be found in the catalogues of jobbers and manufacturers, and knowing the prevailing discount, the net cost may be easily arrived at. Many fixtures, water closets, for instance, are often figured complete, that is, instead of having to figure the crockery, tank, brackets, chain and pull, etc., in detail, a cost price of the entire outfit may be obtained. This is true of other fixtures also - lavatories, urinals, etc.
When so figured, however, the estimator must be careful to note any items required in the specifications which are not included in the combination price.
The estimating of marble and slate may often be made very easy by the use of the table of contents of marble slabs shown under Plate 2. The area found from this table, multiplied by the cost per square foot, will give the cost of the marble required.
Much loss may be sustained if miscellaneous items are not given due consideration, items such as carfare, board, cartage, etc. In some sections of the country the excavating for pipe trenches, etc., and the laying of tile pipe is included in the mason's contract, rather than in the plumber's.
Of much importance to the person who is just entering upon the work of estimating, and desirous of general information, is the method of carrying out costs against the different items in the estimate. Nearly all plumbing goods are sold and billed at a discount from a list price, and in carrying costs in an estimate on plumbing work it is necessary to have not only these list prices, but also the prevailing discounts on the different lines of material. It would systematize the work of estimating and make it far easier if the estimator would bring all these lists together in a book of proper size, so that when it comes to figuring costs, the list price and discount on any material whatever may be referred to without having to refer to numerous catalogues and lists that may require considerable searching for before they can be located. The matter of list prices and discounts on such materials as cast- and wrought-iron pipe, brass goods, etc., has been systematized to a considerable extent during recent years, and is handled more easily therefore. For instance, the lists of standard and extra-heavy cast-iron pipe are so arranged now that one discount applies to both grades, whereas formerly there was one discount on standard and another on extra-heavy pipe.
In order to show how the cost of material may be carried out on an estimate, it will be pertinent to the subject to show the cost figured on a list of soil pipe and a list of soil-pipe fittings.
In the following list, after the style of pipe or fitting is named, is given the list price per foot of soil pipe or the list price per single fitting, then the total number of feet of pipe or total number of fittings reckoned at this list:
20 ft. 2 in. X. H. C. I. Pipe................
50 " 3 " " " "
60 " 4 " " " " ................
25 " 4 " Standard C. I. Pipe.............
Disc 25 %..........................
8 2 in. X. H. Bends......................
6 3" " "......................
4 4" " "......................
24" Standard Bends....................
62" " Ys.......................
2 3 " "
1 3 " X 2 in. Standard Ys. ......................
3 4 " Standard Ys......................
6 4 " X 2 in. Standard Ys...........................
2 4 " X. H. T-Y.......................
1 4 " x 2 in. X. H. Ys....................
2 4 " X. H. Running Traps.......................
3 2 " Inverted Ys.......................
Disc. 30 - 5 - 5%.................
As seen from the above, the discount on pipe is taken on the total pipe footing, and the discount on fittings is taken on the total fittings footing. This is a much less laborious undertaking than the taking of the discount on each pipe or fitting, and there is less opportunity of error.
The discounts that are given on certain lines of plumbing material are often very complex, such a discount as 25 - 10 - 5% being very common. It will be of interest to beginners in the work of estimating to understand the manner in which such discounts are figured out. In the first place, if the above-mentioned discount can be estimated on $1, the net amount remaining after taking the discount may be used as a multiplier for that particular discount.
Thus, when the discount mentioned is deducted from $1 it leaves .6413. Now, if a discount of 25 - 10 - 5% is to be applied to any amount, $50.35, for instance, the net amount derived can be found by multiplying by the multiplier .6413. Thus, $50.35 X .6413 = $32.29 net. Let us see how the net multiplier .6413 was obtained. It is not meant that the three separate discounts, 25, 10, and 5% are to be added together. If this were so, the full amount, 40%, could be given.
The meaning of the discount 25 - 10 - 5% is that 25% is to be deducted from the list price, and from the remainder 10% deducted, and from this second remainder 5% deducted.
This would be a tedious method to apply, and instead of following this practice, the use of a table of net multipliers will be of very great value in the saving of time and labor: 1.00 X .75 = .75, .75 X .90 = .675, .675 X •95 = .6413. This series of operations gives the multiplier desired, the net amount each time being multiplied by 1.00 minus the next discount, the multipliers thus being 1.00 - .25 = .75, 1.00 - .10 = .90, 1.00 - .05 ==.95.