AUBURN — Twin Cities water should be free of fluoride for two months this spring as crews turn off the supply and rebuild the fluoride delivery system.

Mike Broadbent, water treatment manager for the Lewiston Water Department and the Auburn Water District, said he plans to take the Twin Cities’ hydrofluosilic acid supply offline March 16.

“We have to take everything out, we have to cut out a wall so we can get the new tanks in, we have a lot of concrete work inside the room,” he said. “Then we have a type of epoxy that’s resistant to the acid that has to go down. And when it’s cured, we need to get the plumbing hooked up and all new electrical systems replaced.”

Broadbent said he hopes to turn the system back on by May 16.

Water officials have added fluoride to the Lake Auburn output since 1969 after a public vote approved fluoridation. The additive is meant to help dental health and tooth strength.

“We are neutral about the fluoride,” Auburn Superintendent John Storer said. “We are not doctors or dentists and we are not health experts. We don’t know the benefits or pros or cons, but the community voted it in and we apply it according to state regulations.”

Water pulled from Lake Auburn is currently run through the ultraviolet filter and then treated with chlorine before being split into two lines. Each line is treated with a corrosion-inhibiting chemical, fluoride and a chlorine-ammonia compound.

One line is pumped to Auburn’s Court Street station and the other flows by gravity to Lewiston.

Broadbent said he currently adds between four and five gallons of hydrofluosilic acid to the Auburn line and between eight and 10 gallons to the Lewiston line. That brings the fluoride concentration in the Twin Cities’ water supply to about 0.7 parts-per-million.

Broadbent said Lewiston-Auburn could use the dry powdered sodium fluoride to treat the water.

“But that’s messy,” he said. “You need a silo and it makes a mess every day.”

Instead, it uses hydrofluosilic acid. It is easier to handle but the undiluted acid can corrode the water treatment equipment over time.

“Everything that contains it is polyethylene plastic and the acid tends to weaken that,” he said. “It becomes brittle and you end up with leaks. It seems like once a week you are fixing a leak in there. And once that starts to happen it’s time to begin replacing your equipment.”

Residents should not notice a difference, although parents of the very young may want to add fluoride drops to their kids’ water.

“They may want to check with their physician or dentist,” he said. “I’m not a doctor or a dentist but I understand that it’s when they are developing their teeth that the fluoride is most important. But I also know that most of the state is not on a fluoride system. Most use a private well and there is no fluoride there.”