Water is one of the natural resources that support entire creature’s needs in earth. It was also a key element of sustainable living. The important of water is proved by fact that human body were consists of 80% water which makes daily water needs is definitely important. Same thing was happen on earth which also consists of 71 % water.  Unfortunately,  nowadays qualities  as well  as quantities  of  water is getting  poor caused many environmental decline. Those situation is feel quite irony, first is because in one side human are depending on water badly, and in another side, qualities and quantities water have been decreasing because of their own. This environmental issue, especially water was realized by Universiti Kebangsaan Malaysia (UKM) by starting to be a first pioneer in Green & Sustainability Campus in Malaysia.  Although UKM is located in water-rich country, still UKM try to commit to save environment as well as manage its environment aspect. The usage of water in UKM itself is categorized in high level. UKM have around 20.000 students and most of them are dwelling in campus.  For  big  campus  like  this,  UKM  had  one  main  Mosque  which  accommodates  some  daily  worship  of Moslem as the majority one. For activities like ablution, washing and bathing, UKM Mosque had produce quite big  amount  of  grey  water.  Grey  water itself  is residual  water that  still fresh  and can  be recycled for some purposes such as landscape irrigation and cleaning service. One alternative method to treats the grey water is by the usage of filter wells. This paper is trying to analysis and proposes some design of grey water system in UKM mosque in order to save environment. With proper grey water treatment, UKM Mosque will contribute to save water and UKM’s environment. This successful water treatment is also can be an alternative model to apply in another building.