The present invention discloses a water
closet comprising a variable soil exhaust
system which can improve durability and reduce an amount of flush water. The water
closet according to the present invention comprises a variable
siphon soil exhaust
system including: a flexible water bladder installed at a rear side of a bowl to be connected to a
water supply passage, a tension spring for applying an elastic force to contract the water bladder, a variable
siphon tube connected to the water bladder via a bracket to allow soil to be exhausted from the bowl while lifted and lowered by an expanding and contracting motion of the water bladder, and a small tube for connecting the water bladder to the variable
siphon tube; and a cover installed to surround the soil exhaust
system. The cover is formed by
coupling first and second half covers of the same shape and comprises a first port connected to the
water supply passage, a second port connected to the bowl, and a third port connected to a bottom tube laid under the floor; the variable siphon tube has one end connected to the bowl through a
bellows tube and the other end communicating with the interior of the cover; and the tension spring is installed within the water bladder in such a manner that an upper end thereof is fixed to an upper catching portion installed at an outlet of the
water supply passage and a lower end thereof is fixed to a lower catching portion provided on the bracket or a bottom surface of the water bladder.