Water was on in the basement but handles at backflow were off. Began winterization procedure. Defrosting backflow, internals were frozen solid. Also both check valves, one check valve at bottom was able to open, check valve at top right snapped as I tried to turn to the open position. Tried winterizing once backflow seemed fully defrosted still getting no air through backflow. Turned on water in basement to test backflow capabilities and found that bottom check valve that seem to open did not in fact open inside. Informed homeowner that recommended step is to replace backflow then re-winterize. I did inform her that there could be other repairs needed to get winterization fully completed, but this is the first step in getting that done.