After relining potable water storage tanks, many municipal water managers must anxiously await results from a discerning panel of taste testers. A “pass” means a quick return to service. A “fail” means draining thousands of gallons of water, refilling the tank and trying again — with time and budget dollars literally going down the drain.
Having failed on the first try for nearly every water tank it had relined in recent years, Saint Paul Regional Water Services (SPRWS) no longer wanted to leave this final step between immediate or delayed water service to chance. So, when the St. Paul, Minn.-based utility provider recently relined its 500,000-gallon Sterling Avenue water tower, it selected Dura-Plate® 6000.
The 100 percent solids glass-flake reinforced epoxy lining system from Sherwin-Williams Protective & Marine meets the new NSF/ANSI/CAN 600: Health Effects Evaluation and Criteria in Drinking Water standard. SPRWS hoped this factor would prevent a costly drain and refill scenario.
The new NSF/ANSI/CAN 600 standard will take effect in January 2023, reducing the amount of xylene, toluene and ethylbenzene allowed in coatings used for potable water service. Such compounds are the likely culprits when water samples fail taste tests, as panel members may smell or taste a hint of lingering chemicals.
By limiting various solvents in lining systems, the standard will help tanks pass taste tests much more readily. As a result, more 100 percent solids coating technologies will likely be specified for potable water service.
Applicators from TMI Coatings installed the Dura-Plate 6000 lining system inside SPRWS’s tower and restored its exterior using a zinc/epoxy/polyurethane system with excellent color and gloss retention.
To minimize the tower’s time offline and stay ahead of the rapidly approaching winter, SPRWS used fast-curing coating systems, including the new 100 percent solids lining system. Applicators were able to spray apply Dura-Plate 6000 at 30 to 40 mils dry film thickness (DFT) in a single coat and up to 125 mils DFT where needed to fill in any pits. The lining’s glass-flake reinforcements give it extremely low permeability and excellent abrasion and chemical resistance, delivering a life expectancy greater than that of a conventional three-coat zinc/epoxy/epoxy system. Helping the project’s accelerated timeline, the lining offered a 10-hour return-to-service time plus the likelihood of passing the first taste test.
In selecting the solvent-free Dura-Plate 6000 system, SPRWS hoped to fill the Sterling Avenue tank just once to realize a timely and less costly return to service. Thankfully, the water panel approved the first samples, enabling immediate approval for service. That’s half a million gallons of water that could be used instead of being drained away.
Occurring just 30 days after the restoration commenced, the return to service was also accelerated by fast curing times for both the lining system and the tower’s exterior coatings. WW
The Sherwin-Williams Company is a global provider of protective and marine coatings, offering a complete line of high performance coatings technologies to combat corrosion. Learn more at www.sherwin-williams.com/protective.
Published in WaterWorld magazine, December 2021.