Installation Differences

• The bowl and tank of two-piece toilets are normally packed in separate boxes by the manufacturer. You can first attach the tank to the bowl and install the complete unit together, as you must do with a one-piece unit. You also have the additional option of first installing the bowl to the floor, then adding the tank on top. This option makes the installation a bit easier, regarding the necessary lifting.
  
  

Leaks

• A one-piece model does not have the tiny crevice between the tank and bowl like a two-piece model. This area is a potential source of leaks if the tank is not initially installed properly on top of the bowl. The holes containing the tank-to-bowl bolts also may leak if they are loose, or if the rubber washers deteriorate.
  
  

Cleaning

• Because the tank and bowl are one continuous unit with one-piece toilets, cleaning is generally simpler. A two-piece model causes the need to reach between the tank and bowl, to wipe away grime and eliminate odors.
  
  

Price

• Flushing power and economy are basic considerations with toilets. One-piece toilets tend to be more expensive than two-piece toilets when you are looking at comparable flushing levels.