In this work, we employ resin 3-D printing to rapidly create reliable and reusable microfluidic components and combine these with our silicon chip -based electrochemical sensor platform. We minimise potential errors by automating the entire microfluidic production process and developed a single step process for alignment with the on-chip sensors. To understand the effect of flow on solid state electrodes operating in generator-collector mode (analogous to ring-disc systems) we undertake a finite element study on the application of electrochemical pH control under hydrodynamic systems. We then confirm this theoretical study experimentally and demonstrate its feasibility through pH dependent chlorine detection under these hydrodynamic conditions. An iterative feedback approach allowed the microfluidic elements to be tweaked and optimised. An additional advantage of the 3D-printed modular approach is reusability, i.e., it allows the system to be disassembled, cleaned and a new chip inserted as required. This is possible as the elements are not irreversibly covalently bonded to a chip surface (such as in soft-lithography) thereby increasing the sustainability of this approach. A commercial colorimetric free-chlorine detector was used to confirm results.