Indian water closet (IWC) is a toilet that disposes of the waste matter by using water to flush it through a drainpipe to another location. Modern toilets incorporate an 'S' bend, this 'trap' creates a water seal which remains filled with water between flushing, thus providing a hygienic barrier by preventing sewer gases from passing up the drainpipe. During flushing the 'S' bend also provides siphon action which helps accelerate the flushing process. However, since this type of toilet does not generally handle waste on site, separate waste treatment systems must be built.