To achieve a zero emission of water with nutrients and plant protection products, recirculation of water in the greenhouse system is obligatory and discharge should be minimized. In this study it was investigated if applied cleaning products may accumulate to harmful concentrations and hamper plant growth. An enquiry amongst growers gave insights in the use of various products. This enquiry showed that most products are used in low concentrations to remove biofilm from piping. Laboratory tests have been executed to investigate if a side effect could be seen to eliminate pathogens. It appeared that the applied, low, concentrations to clean the pipework had no side effect in eliminating of pathogens. In a greenhouse experiment it appeared that sodium, chloride and chlorate can potentially accumulate, while chelates are partly broken down. Measurements at commercial gerbera farms showed that no accumulation took place to harmful concentrations.