Mattlin was forced to close mid-morning on Friday when a water main near the entrance to the school on Washington Avenue burst, leaving the school without running water. State law requires running water in schools at all times.
Plainview School officials decided to transfer all of their students by bus to Plainview Middle School to complete their school day Friday.
Meanwhile, a Water District crew got to work on the break and discovered the cause to be a crack in a valve that fed the school, said Water Commissioner Andrew Bader.
In cooperation with the district, workers installed a replacement valve and a second, or redundant, valve so a similar future problem could be quickly rectified, Bader said.
The water district is absorbing the cost of the second valve, Bader said.
"There was a great deal of cooperation and quick thinking on the part of the school district and our crews," Bader said. "We all coordinated very well."
The work was completed in a matter of hours.
Mattlin will be open Monday morning for classes as usual, the district announced.