Toilet is a critical link. The problem of body waste disposal is a subject that has always necessarily been the prime concern for humans living in society. Considering the evolution of the toilet is important for comprehending toilet design today and especially the deficiency of it. The idea of toilet is distinctly connected with the concept of cleanliness. The theory of bacteria and the rise of scientific thought gave rise to the concept of 'hygiene' and its appearance in daily life, which in turn altered the inside view of dwellings. Toilet is a vital part of this home system, distinctly related to human and environmental factors. Basically, the toilet is a machine for mixing faeces, urine, toilet paper, and water. This machine can be equipped with a number of accessories, but whatever its shape, in fact the WC is more than an object based on the idea of disposal of flushing away and hiding or diluting something we do not want. It is obvious that the disposal of waste can only be a part of 'toilet design'.In the history of the toilet, the main problem has remained the disposal of human waste at city level. This was assumed to be solved when the sewerage system was introduced. In fact, the world has yet to deal with environmental problems. Ecological sanitation offers a solution to toilets' share of pollution. Moreover, the addition to ecological conditions, it is important to design a toilet by thinking in a way regarding human psychological and physiological needs.For taking toilet design a step further, this research aims to reveal criteria to solve sanitation problems by focusing on the entire mechanism including, the toilet and toilet system, which should be considered and designed to serve all needs of cultures, ages, differences as a part of everyday life, to be adopted in varies occasions adding to global needs and realities.especially to reach 'the ideal toilet'.