Flush-Aid Part A is a flush water additive for the fresh water tank. It keeps the water fresh to ensure better flushing. Flush-Aid Part A leaves a protective film in the bowl and on the valve, and has a cleansing effect. Flush-Aid Part B reduces the build up of gas and unpleasant smells, and prevents deposits forming on the inside of the waste tank. It helps break down waste substances and toilet paper, to make emptying easier.