A one-piece toilet is a style of toilet where the tank or cistern is connected directly to the bowl, so it is one full unit, whereas a two-piece toilet is made up of two separate units, which are then joined. This means the installation process of a one-piece toilet is easier, as it just needs to be connected to the water supply on the wall and fitted correctly to the drain on the floor. This is made easier by the fact that the toilet is more compact, as the tank is considerably smaller than most other toilets.
Another big advantage of the one-piece toilet is that because the tank is fused with the bowl it is more durable and is less likely to leak or break. So, even though these benefits come with a higher price tag, the pros can be that you may spend less money on a plumber if things go wrong.
Keeping these toilets clean is super simple, as there is no crease or joint between the tank and the bowl (like on a two-piece toilet) for fluid or waste to get trapped between. If you wanted to get in there to clean it on a two-piece toilet, you may have to remove the tank which can lead to breakages.