When washing polyester the temperature of the water for washing 100 percent polyester is 40 F degrees.
You can wash polyester in warm water but to prevent shrinkage of the polyester you should never wash the polyester in a water temperature of more than 60 F degrees.
The hotter the water when washing polyester the more chance you have at shrinking the polyester.
As long as you keep the water temperature of the washing machine cooler than 60 F degrees when washing the polyester you should have no issue of shrinkage.
However if you do want to shrink 100 percent polyester you can get the polyester wet and then dip the polyester in hot boiling water for a minute or so.
The boiling water will shrink the polyester if that is what you want.