Students will need to find another place to leave their mark: The town plans within four years to demolish the water tower that’s painted annually to honor local high school seniors.

It’s hard to miss the blue-grey tower on Maynard Road, which currently reads “Class of 2013” in huge black letters. It tops out at 165 feet, overlooking football games and track practices from just southeast of Cary High School.

“It’ll be about the middle of June, and all of a sudden the email starts: ‘When are they going to paint the water tower?’ ” said Doug Thilman, the school’s principal.

Both the school campus and the tower were built in the 1960s – and that means both are due for an upgrade.

The school campus will eventually get several new buildings, but there’s no future for the water tower, which will instead be torn down in the next three to four years, according to Cary Engineering Director Tim Bailey.

At almost 47 years old, the half-million-gallon water tank is too old and too small to continue its crucial mission of storing water and regulating pressure, according to town staff.

It wouldn’t be cost-effective to strip and repair the tower, Bailey said, so the town instead is planning a new million-gallon tank behind the Cary Village Square Shopping Center near Walnut Street.

What this means for the Cary High School tradition is unclear, but news of the change may rile parents and students who have grown attached to the decades-old custom.

The practice may even predate the school’s current campus and the water tower in question. Fifty-five years ago, Cary High School students illegally printed “Class of 1957” on an elevated tank, one alumnus recalled.

The guilty parties were forced to paint over their graduation prank the next day, Floyd Morgan told The Cary News during his 50-year high school reunion.

The painting of the Maynard Road water tower also has illicit roots. It’s unclear when students first painted the tower, but they surely didn’t have permission.

“It was kind of a contest for rising seniors to see how they could get in and put their class on it,” said Ron Singleton, former Cary utilities director, in 1992. “We finally reached a compromise: We’d have it painted professionally if they wouldn’t climb the tank.”

The town officially took over the painting in the mid-1980s. The local government spends about $1,100 a year to update the paint job for another crop of graduates.

An unknown vandal painted “420” on the tower in 1999, prompting debate about the meaning of the number. The town painted over the graffiti.

Thilman, the principal, hasn’t yet considered a replacement for the tradition. And Bailey, the utilities director, said there isn’t another obvious public venue.

While the local government “has many other tanks and facilities, none are similarly visible to school and outdoor sports fields,” he wrote in an email.

So the tradition, perhaps, will die with the water tower, or Cary High School may find another outlet for its creativity.