HSI’s chlorine sensor does not require reagents or a waste stream, lowering maintenance and installation costs. Colorimetric systems, such as the Hach CL-17 require reagent replenishment every month and periodic replacement of pump and optical components. These can be difficult to troubleshoot, and the tubing is subject to biofouling requiring replacement. Reagents and parts can exceed $600 per year plus labor. Most competitor amperometric sensors often still require membranes and electrolyte and so do not reduce maintenance or water waste. Unlike the MP5, at time of writing no other amperometric chlorine sensor is approved for NSF-61 usage in drinking water without a required waste stream.