Whether the tank can be separated from the bowl determines the primary difference between one-piece and two-piece toilets. Traditional toilets are two-piece products purchased separately and then connected at installation. One-piece toilets are a more recent product development.
The two-piece toilet is comprised of the bowl and the tank where the toilet's mechanical components and water for flushing are located. The two are joined together when installing the toilet.
The one-piece toilet has its bowl and tank molded together as one device. The internal mechanics of the one-piece toilet are not dissimilar from the two-piece and function on the same flushing principle.
One-piece toilets have significant advantage in cleanliness as they do not have a gap where the tank and bowl components meet. This eliminates difficulty in cleaning hard-to-reach areas that may harbor germs and stains.
Many homeowners prefer the sleek, low-profile of one-piece toilets as a contrast to the more traditional and taller two-piece toilet. However, two-piece toilets are still more prevalent and offer a larger variety of styles and colors to the buyer.
Comparable two-piece toilets cost less than their one-piece counterparts.