The single tub does all the washing and drying tasks in one tub. This tub has two layers: inner and outer layer that comes with holes that help to drain water. Its mechanism is simple and takes less space.
The most common variety of semi-automatic washing machines is the twin tub. The two tubs locate next to each other, where one is used for washing and the other for drying. It requires manual effort to move clothes from one tub to another during the washing process.