Clogging Potential of Low-Flush Toilet Drain System

Abstract

Water scarcity is a global issue. In residential buildings, water closet appliances share the biggest portion of water consumption. Therefore, they are targeted for improvements to consume less water while keeping acceptable performance. Low-flush toilets (6/3LPF) consume a significantly smaller amount of water compared to their predecessors (13LPF). However, lower water flows pose challenges like unreliable waste transportation and frequent clogging in old drainage systems. Furthermore, it is not economic to upgrade an entire drainage system to adapt to the new generation of toilets. In addition, recently there was rapid increase in the use of toilet friendly sanitary products. Their impact on the drainage system, especially with reduced flushing of volume is still a research subject. This study was divided into two parts. In the first parts the clogging potential was defined for two toilet models and the effect of the related hydraulic parameters was evaluated. After, the minimum flushing condition to carry the waste samples without clogging was calculated and the clogging charts were created. In the second part, the hydraulic characteristics were defined for two toilet models. Next, the clogging potential was calculated for selected toilet paper product as representative of flushable sanitary products. Moreover, the relation between the toilet hydraulic characteristics and the clogging potential for the toilet paper products were investigated. Finally, in both study parts it was shown how the results can be used in real practice and how it can help in reducing water consumption while maintaining proper waste drainage. The study in the first part showed flushing volume to have the greatest impact on clogging potential followed by pipe diameter and finally slope. Using the clogging charts it was shown by example how to calculate the minimum flushing conditions in cases where there is slope limitation, or flushing amount. In the second part of the study the clogging potential for the toilet papers also was influenced by the flushing volume more than slope. Furthermore, the flow profile was chosen to represent toilet characteristics and further simplified into two values namely C.g. and Qmax. The analysis showed that toilet model with more peaked and short period flushing waves have lower clogging potential than toilets with flatter flushing waves.