When we first introduced the Smart Recirculation Control tankless water heaters were not nearly as popular as they are today. Installing the flow meter on a tank water heater simply entailed disconnecting the flexible cold water hookup line, threading the flow meter onto the tank, and reconnecting the flexible hookup line.
But many time tankless water heaters are installed with hard copper piping right up to the water heater not allowing any way to easily disconnect the cold water feed and install the flow meter.
In these installations, we recommend that the flow meter be installed in the copper piping with union fittings on each end to facilitate easy removal and replacement rather than threading it onto an NPT fitting and soldering it into place.
Not that we have had failures of the flow meter, the failure rate is exceedingly low, but they are a mechanical device and if there is an issue which requires removal of the flow meter, you will be very happy that there are union fittings to facilitate easy removal.
→ Check out our installation guides.