A below grade trench drain system and a method for making the trench drain system is disclosed which does not rely on the contractor's prowess to dig a trench with a proper slope. The trench drain system, in accordance with the present invention, includes a plurality of modular trench sections formed with a uniform exterior height and an interior fluid channel formed with a pre-sloped floor. As such, the trench drain system, in accordance with the present invention, can be installed in a level trench, which greatly simplifies installation by the contractor and ensures that the trench drain will be installed with the proper slope. The modular trench sections can be coupled together forming a trench drain with a continuous slope or alternatively coupled with modular trench sections with no slope to form a stepped slope. The configuration of the modular trench sections allows the modular trench sections to form a trench drain system sloped in different directions to enable connections to the common drain in the center as well at both ends. As such, the trench drain system provides more configurations for connections to the common drain system thus improving the flexibility of the system and at the same time provide a trench drain system which does not depend on the installation prowess of the installation contractor.