I'm looking at installing an outdoor tankless water heater (Rinnai). The installation manual recommends installing auto drain down solenoids so that if the power fails the unit will drain and not freeze. Has anyone done this type of install? What type of solenoids did you use and where did you get them? Any advice you can provide would be greatly appreciated.
I'm located in the Atlanta, GA area, so we rarely get temperatures below freezing... but I'd like to be prepared just in case.