Where—
c = cost per bbl. of cement, or $4.45.
n = cu. ft. in one bbl. (taken at 3.5 here).
s = ratio of sand to cement, or 4.
d = inside diameter in inches.
t = thickness of pipe in inches.
l = length of pipe considered, or 1 ft. here.
Then:
| c × l × π × (dt + t²) | ||
| Cement-cost per foot | = | ——————————————, |
| n × s × 1.1 × 144 |
which gives here =
| 4.45 × 1 × 3.142(dt + t²) | ||
| ——————— | = | 0.00631(dt + t²). |
| 3.5 × 4 × 1.1 × 144 |
This gave the following cement costs per lineal foot:
| Diameter, ins. | Thickness, ins. | Cost per foot. |
| 6 | 1¼ | $0.0571 |
| 8 | 1¼ | 0.0730 |
| 10 | 1⅜ | 0.0998 |
| 12 | 1½ | 0.1278 |
The sand cost was based on 15 cts. per cubic yard for loading, and a haul of two miles of 1 cu. yd. to the load, making five trips per day, at $4 for man and team. It bears a constant ratio to cement cost, being 11.2 per cent. of the cement cost. The labor cost of making was based on the foreman's estimate that a foreman, tamper, mortar mixer, and water man should finish 250 joints a day of 6 or 8-in. pipe. For the 10 and 12-in. pipe, the labor was assumed to be greater in proportion to the material. The foreman was taken at $3, one man at $2.50 and two at $2. The cement for painting the inside was neglected. Hauling the pipe to place was taken at twice the cost of hauling the sand per mile, and a haul of 4 miles was assumed. The cost of laying was based on a foreman's estimate of 2 cts. per foot for trench, and that one man to lay, one man to plaster the joints, one helper and one man to back-fill would lay 600 ft. per day of 6 or 8-in. pipe. The larger sizes were assumed to cost more in proportion to their material.