This paper presents valuation items for drainage performance of horizontal branch pipes. Experiments were conducted using drainage headers which are normally adopted in KSI housing in order to investigate the effect of low slope on drainage performance. A survey was followed up using the KSI houses as objects. Some comparisons on drainage performance were made between low slope and normal slope, and between the newly built houses and one year after the houses used. The practicality of low slope horizontal branch pipes is discussed.
