Plastic Water Tank 2 (Polygon mesh 3D model) is available on CGTrader for $9. Original author: xtreme3d. Specs: 874 polys, 939 verts.
BLEND (Blender, filesize: 192 KB), OBJ (OBJ, filesize: 18.8 KB), 3DS (3D Studio, filesize: 28.8 KB), DAE (Collada, filesize: 110 KB), STL (Stereolithography, filesize: 87.8 KB)