Vertical or horizontal flow gravel beds can be used in water treatment as roughing filters. In order to improve the performance of horizontal flow roughing filtration (HRF) this process has been modified earlier by applying a constant coagulant dose prior to filtration named direct horizontal roughing filtration (DHRF). In this research a lab scale DHRF pilot plant was used for investigate DHRF performance. The study results indicated that DHRF (6.5 m long consisting of 2.5 m first compartment with 12-18 mm diameter grain, 2 m/s compartment with 8-12 mm diameter and 1.5m third compartment with 4-8 mm diameter) was systematically yielded good effluent quality (<2NTU, C.I=0.95) with raw water quality of 200-400 NTU. DHRF is a versatile pretreatment process capable of handling wide fluctuation in raw water turbidity (200-400 NTU) while operating condition such as coagulant dose [2mg Fe (III)/L], mixing intensity, time and filtration rate remained unchangeable.