Ablution process consumes a huge amount of water especially in mosques for cleaning certain part of the body before performing prayers. The high volume of ablution water produced in mosques and its low strength in quality makes it a feasible option to be reused. This paper introduced an assessment of conventional filtration (sand and gravel) in treating ablution water for reuse purposes and its water savings potential in mosques. The treatment system has assessed its capability for reuse and its water savings potential. A pilot scale of filtration system was developed and was run with the ablution water from the Parit Raja mosque and the Pintas Puding mosque. The samples were taken during Friday noon prayer between January to March 2013. The efficiency of the conventional filtration system was tested for the effluent quality of NH₃, TSS, COD, and BOD. The case study of water savings estimation for the proposed system was undertaken at Pintas Puding mosque. It was determined based on the quantity of ablution water, water consumption, water demand, and water bills record. The results deduced that the conventional sand filtration can improve the water quality parameters; 0.60-0.05mg/L reduction of nitrogen ammonia (NH₃), 6.0-1.53mg/L of suspended solids (TSS), 3.12-0.15mg/L of chemical oxygen demand (COD), and 27.67-4.16mg/L of biochemical oxygen demand (BOD). The treatment system was projected to save water consumption by 41.73% and RM180.16 of water saving per month. Water consumption was estimated to be further reduced to 50.83% if reused activities such as irrigation and toilet flushing were applied. Hence, annual water savings could reach up to RM2161.92 per year. With the current instability of water resources, the implementation of the conventional filtration system for ablution water in the mosques provides water security and water resources conservation option for the country.