SAVING MAINTENANCE COSTS

Photo courtesy of Engineering America

In 1983, the City of Webster, S.D, installed a 62-ft-dia x 24-ft-high, 530,000-gallon, glass-fused-to-steel tank to store potable water.

Selected because of its low maintenance costs, in 1983 the City of Webster, a small community of 2,200 residents in South Dakota, invested in a glass-fused-to-steel reservoir to store its potable water. “After 32 years you can see the tank looks brand new,” says Webster Public Works Director Arlie Larson. “With all the responsibilities that we have as a municipality it has been great to have one less thing to worry about and that has been our glass-fused-to-steel reservoir. As with every tank in service in our system, every three years the tank is visually inspected and cleaned of any sediment build-up.” The Aquastore Life Cycle Estimator allowed Larson to forecast any future expenses related to maintenance of the tank.

In terms of life-cycle cost estimates that compare this 62-ft-dia x 24-ft-high glass-fused-to-steel tank to a painted welded tank of the same size, Webster’s choice makes even more sense. Maintenance costs differ widely between the two tanks. Repainting the interior and exterior of the welded tank costs more than three times as much as replacing the interior and exterior fillets (sealants) of the glass-fused-to-steel tank. (In the case of the Webster tank above, and many other tanks of the same age around the country, it should be noted that no fillet replacements have been required to date.)

Accounting for NPV (net present value), and assuming three painting cycles for the welded tank and two to three fillet replacements for the glass-fused-to-steel tank over a 60-year time span, the glass-fused to-steel tank maintenance costs would add up to $266,000, while those of the painted welded tank would amount to $906,000—this represents a significant difference of $640,000 over the 60-year life of the tank.