There is no "graffiti wall" in the town. Mr McWilliams says such a thing just encourages taggers to move their tagging on to nearby property.
But the most interesting discovery, according to Mr McWilliams, is that taking ownership of a public wall means the space gets respect.
The council has teamed up with Wai Art and now, instead of blank walls, many public spaces in Carterton feature works from artists such as Anna-Marie Kingsley and Sandra Wong as well as Carterton School pupils.
"People used to tag these walls, but no one has tagged them once since the paintings went up," Mr McWilliams said.
"It's about taking ownership."
Mr McWilliams takes pride in being able to paint over a tag within four hours.
"They put it up, we paint over it. It doesn't bother me."
The council has plans for more art work to go up in the town in the future and will continue to make sure that tagging is not a problem in Carterton.