Watch the Hach Ground Water Rule (GWR) Video! Hach has the easy solution for GWR chlorine monitoring. Our CL17 chlorine analyzer measures either Free or Total chlorine, using DPD chemistry which is EPA approved. The CL17 is easy to use and maintain and replacing reagents and tubing is quick and simple. It requires no calibration because it automatically takes a zero reading prior to each sample. Because it does not use probe technology, there are no membranes to foul or replace. Finally, it leverages Hach’s 60 years of water quality analysis experience. For more information, visit: www.gwrule.com