Prelude offers a new approach to internal cleaning that introduces the option of single or multiple flushes with lower volume. This method is not possible with conventional enemas, because they are discharged too quickly, the contents of the flask are released. The Prelude solves this with a special slow flow one-way valve that slows the flow of liquid and prevents the flask from filling with air. The valve also ensures hygienic operation and prevents backflow of liquid into the flask. Prelude makes this possible and provides easier, faster and more convenient cleaning.