Kingdom of Saudi Arabia (KSA) is one of the countries possessing the highest number of medium to mega mosques. Public ablution ritual is such mosques consumes very large amount of water coming from tap water supplied mostly, from expensive desalination plants mixed with barely, renewable groundwater. Significant portion of taps are usually left running during ablution leading to wastage of huge amounts of clean water. The enormous volume of very low polluted grey water generated is unnecessarily allowed to freely drain away to public wastewater treatment plants (WWTP). This increases the pressure on the WWTP units as well as their operating costs. Thus, the need to adopt a sustainable approach to salvage huge volume of precious and costly water resource, while achieving significant reduction in wastewater that goes to domestic WWTP, cannot be overemphasized. This paper presents a proposed redesigning of ablution and toilet area of a mosque via introducing a recycling system for treating collected ablution grey water for reuse within mosques premises. The proposed close-loop system would be used for non-portable toilet flushing usage by worshippers attending the mosques services and also for landscaping for mosques beautification. Unlike other design, the presented design idea is a robust solution that would integrate low cost and sustainable engineering solutions into the overall management of mosque water system. This redefines the engineering design of mosque toilet and ablution area architecture for contribution towards meeting KSA sustainable development target goals.