Dispensing techniques utilize existing fluid to dispense a solid block of chemical product concentrate. The solid chemical product concentrate may include, for example, detergents, disinfectants, sanitizers, rinse agents, or other cleaning agents. The dispenser monitors and controls the concentration of the chemical product in a use solution. When the concentration of the use solution falls outside of a target range, the dispenser routes existing fluid from within the system to the dispenser, where it interacts with and dispense a solid chemical product concentrate, thus raising the concentration of the chemical product in the use solution. In a dishmachine application, the existing fluid may include post wash or rinse fluid from the dishmachine, or may include use solution from a sump, tank, or other use solution storage container.