where to find coag solution

I recently moved into a house that has a coag water treatment system for the well water. It has two tanks that supply chemicals to treat the water. one is labeled caustic soda/chlorine, and the other is labled "coag". Where do I get these chemicals from? The chlorine is easy but what about the caustic soda and coag ?

Usually any local independent dealer or some online dealers. You find local dealers under the heading Water in your yellow pages.

Then you'll need to know how much to use to make up the solution.