Age of Steam Roundhouse
Roundhouse Reports
Other than a steam loco, nothing says "Old-Time Railroading" more than a wooden water tank—Part 1
By John B. Corns
During the days of steam locomotion every railroad faced the same problem—supplying water to locomotive tenders while the generation of steam by the locomotive constantly emptied the tenders. At one extreme, several first class lines (most notably New York Central and arch rival Pennsylvania) built between-the-rails track pans so that locomotive tenders could lower a scoop into a long trough of water to take water "on the fly" without stopping speeding passenger consists. At the other extreme, some backwoods short lines dropped suction hoses into lineside streams to lazily syphon water up into tenders. Most railroads fell somewhere between and erected elevated water tanks at strategic locations, allowing the force of gravity to quickly supply fresh water down into nearly empty tenders. When located in remote areas, a few houses and stores would occasionally spring up next to these trackside watering facilities, giving rise to the term "tank town."
Water tanks were constructed of a size suitable to provide ample storage considering locomotive tender size, frequency of refilling, and the source of the water. When located near cities and supplied by a constant source (such as a municipal water system), water tanks could be made smaller because they could be filled rapidly. In areas where the capacity of the ground water source was minimal or irregular, a larger tank would be built for a slow, continual refilling to assure that a sufficient quantity of water was always available for tenders. Also, by using larger tanks, some railroads were often able to get through third trick (night shift) without refilling the tank, thus saving the cost of an additional employee (a water tank pumper) during the least busy time of a 24-hour day.
Originally, all wooden water tanks were built to a slightly conical shape with sides that tapered inward toward the top. The vertical wooden boards in the tank—called "staves"—were tapered, and when assembled, the top of the water-holding "tub" was narrower than the bottom. This was necessary because huge, metal, reinforcing hoops that held the tank together were riveted to their required diameters—widest at the bottom with hoops of gradually diminishing diameters used toward the top—and then with hammers, driven down onto the tapered tub sides until the staves were squeezed together and the fit was tight, just like the construction of a wooden barrel. At the turn of the 20th century and the adoption of sectional, adjustable hoops that were easily bolted together end-to-end, the huge, riveted hoops and tapered staves were no longer needed. Cylindrical-shaped water tank tubs were easily constructed with their circular tops and bottoms having the same diameter, and with truly vertical sides.
Because the cylindrical design was stronger, required less reinforcing than other shapes, and was less expensive to build and maintain, it soon became the industry standard. Because wood was inexpensive, easy to work with, and readily available, lumber was the most common material for erecting railroad water tanks, but each road had its own construction requirements due to geographic, climatic and operational differences. High quality, air-dried lumber that had no knots and no excessive sap was preferred for the tub, with white pine being an economical substitute for "perfect" cypress and redwood staves that were scarce and expensive. Water tanks constructed of untreated lumber were usually painted on the outside of the tubs, while their interiors were either left unpainted or coated with pitch to increase their service life. The American Railway Engineering Association (AREA) set criteria for materials and methods of construction of water tanks, railroad structures, appliances and equipment.
Properly treated and maintained, a water tank's white pine tub lasted about 20 years, twice as long as supporting timber framework holding up the tub. Wooden tubs usually began to rot from being allowed to dry out, so they were constantly kept full of water to retard decay. Since tubs were not generally filled to the very top, and since the top ends of the staves were deprived of water more often than the bottom ends, the staves' upper ends began to rot before the rest of the tub. During the 1920s, creosoted lumber for water tank tubs became popular as this permitted the use of cheaper grades of timber during initial construction. Many railroads also adopted treated lumber for construction of the supporting tower framework to reduce the initial cost and long-term maintenance.
Wooden staves for the tub were nominally from 6 to 8 inches wide and of a length suitable for the capacity of the tub. AREA standards required stave thicknesses of 2-1/4" for 50,000-gallon tubs and 3" for 100,000-gallon tubs. (Appropriately, Age of Steam Roundhouse Museum's 50,000-gallon capacity water tank uses staves made of 2¼"x 6" Western Red Cedar.) Stave side edges were cut or planed on radial lines from the centerline of the tank to assure tight joints between the staves when assembled. Also, the inner and outer surfaces of each stave were "surfaced" to the true circle of the water tank so that the tub was a true, curved cylinder, not a tube having 150 staves with 150 flat outer surfaces! The inner surface of each stave was milled with a 5/8" deep "croze" (channel) measured 4" from the stave's bottom end to accommodate the tank's 3-inch thick floor planks. The flooring's plank ends were cut to the true circle of the tank for a tight fit into the croze. All wooden joints were precisely framed so that the tub structure would be totally watertight without needing caulking compounds to plug leaks.
The vertical wooden staves were held tightly together by hoops of rolled wrought iron whose cross-sections took shape as round, half-round, oval or flat. Each complete hoop consisted of six separate, shorter sections that, when bolted together end-to-end, formed an entire circle of hoop. Each end of each hoop section was threaded so the sections could be held together with turnbuckles or other tensioning devices (called "lugs") to tighten the entire hoop and form a full circle. (This was easier than handling and installing the old, heavy, 24-foot diameter riveted hoops.) The tightened hoops maintained stave rigidity, provided the tub's cylindrical shape and provided overall strength with no interior bracing. Because of the weight of the water pushing down from above, the pressure of the water in the tub was greater toward the bottom of the tub. Spacing between the hoops around the top half of a 50,000-gallon tub was about 20 inches and decreased to about a 9-inch spacing toward the bottom. Hoops were rolled into 3 diameters: 1-1/8" for use toward the bottom of the tank where the water pressure was the greatest, 1" hoops for the center and 7/8" hoops for the top of the tub where the water pressure was the least. Iron hoops lasted ten years or so, rusting generally on their inside surfaces (against the wood) where paint and preservatives could not be applied and where inspection and maintenance were difficult. For these reasons, hoops with the smallest surface contact with the wooden staves (i.e., hoops with round cross-sections) rusted less and lasted longer. In fact, more water tank failures were caused by faulty hoops than for any other reason.
Attached to the outside of the tub was vertical depth gauge as a visual indication of how much water (measured in feet) was in the tank. A float inside the tub raised and lowered with the changing water level, and a rope and pulley at the top of the tub connected the float with a weighted depth gauge pointer outside. When the tank was full, the float rode high on the water inside the tub and the pointer was at the bottom of the gauge. As the water was used and the tank was emptied, the water level and float moved downward, causing the pointer to move upward on the gauge, the opposite of what most people expected to see. For this reason, the depth gauge numbers were reversed from top to bottom, with the largest numbers being toward the bottom of the gauge. Of course, gallon-for-gallon, a foot of water in one tub did not equal a foot of water in another tub having a different diameter.
The water tank was usually built with a roof to retain heat in the winter and to keep birds, leaves and dirt out of the water supply. Roofs were generally shingled, and were equipped with a hatch for access to the interior of the tub. An interior ladder was provided down into the tank, while a separate, external ladder extended from ground level up to the roof. A ball, spire or other fancy decoration called a "finial" adorned the top of the roof's peak.
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