Pimlico spokesman David Joseph says officials are working to correct the water-pressure problem.
It was unclear how much of the track was affected by the water-main break Saturday. Officials said the clubhouse, the first floor and the Rogers Building all have water, and the horses have plenty of water.
A crowd of around 100,000 packed Pimlico on a day in which temperatures in Baltimore hovered around 80 degrees.
In 1998, an electrical outage stopped betting machines and shut down air conditioners on Preakness Day.