Plain water is proven to work extremely well, but our units will accommodate most agents. A small amount of mouthwash can be added to the water for flavoring and/or to enhance compliance. Any solution used should be at room temperature for greatest comfort. Chlorhexidine and Listerine are two that have been clinically tested in the Waterpik Water Flosser. Chlorhexidine can be diluted in varying strengths. When a patient uses an agent like these, they will need to flush out the unit with water after each use. Failing to do so may shorten the life of the unit.