SULTAN — The city will begin fluoridating its drinking water next month as it taps into Everett’s drinking-water supply.

Sultan expects its growth will eventually exceed the amount of water that its own system can provide. During maximum summer usage, city businesses and residents use about 1.2 million gallons a day, all the city’s water plant can handle.

So Sultan is turning to Everett, which already distributes water to about 450,000 people, including residents of Monroe.

Because Everett fluoridates its water for the reduction of dental cavities in children and adults, Sultan officials decided to fluoridate their own water supply.

“If we started mixing fluoridated water with nonfluoridated water, then it wouldn’t be mixed equally,” said Connie Dunn, Sultan’s public-works director. “We decided that since many people give (fluoride) drops to their children, we were going to match the city of Everett.”

Residents will no longer need to supplement their diets with fluoride drops or tablets, said LeeAnn Hoaglin Cooper of the Snohomish Health District’s oral-health program. Cooper advised Sultan city officials on fluoride treatment.

Cooper said it will be important for Sultan to fluoridate its water because Everett’s water is injected with the recommended allowance to prevent tooth decay. Otherwise, mixing the water would dilute the amount of fluoride people received, keeping it from working adequately, she said. But it would still be enough fluoride to prevent dentists from recommending supplemental doses because too much fluoride can damage teeth.

Though decisions to fluoridate water were controversial when many major cities across the nation began doing it, there has been little concern expressed in Sultan, Dunn said. The city held a public meeting last month to explain the process and the city’s reasoning, but few people attended.

The city will invest about $20,000 in equipment to begin fluoridation, Dunn said. That includes storage facilities and an injector that adds fluoride in proportion to the flow of treated water. That will maintain a constant, safe level of fluoride in the water — typically 1 part fluoride per 1 million parts of water. At 4 parts per million, fluoride can begin to mottle teeth.

The cost of the fluoride should be minimal to the city, said Jim Miller, an Everett engineering superintendent. Everett began fluoridating its water in 1992 and spends $5,000 a month for about 10,000 pounds of fluoride.

Sultan doesn’t plan a water-rate increase to pay for fluoridation, Dunn said. The city, however, is conducting an overall rate study for other improvements to the drinking-water system that could recommend a rate increase eventually.

The health district and dental and medical associations recommend the addition of fluoride to water for dental health, but there are still places in Snohomish County that don’t use it, including the Stanwood area, the Tulalip Reservation, Darrington, Gold Bar, Index, Lakewood, Maltby, and sections of the Marysville area, Arlington and Bothell.

“There’s no particular reason they don’t do it, just like Sultan didn’t,” Cooper said. “They’re just smaller water districts.”

In Washington, about 75 percent of the population has access to fluoridated water, according to the national Centers for Disease Control and Prevention.

For residents who don’t want fluoride in their water, Dunn recommends purchasing a filter for the kitchen sink tap that can remove most of the additive. Filters can run between $400 and $1,500, Dunn said. Residents can also buy bottled water, which generally doesn’t contain fluoride.

Fluoride in the water is not a substitute for regular brushing and visits to a dentist, Cooper said. Evidence has shown that fluoride, combined with healthful eating and brushing, can reduce cavities by 25 percent, she said.

Christopher Schwarzen: 425-783-0577 or cschwarzen@seattletimes.com