I am guessing the water heater bypass valve has been switched over? If it has then maybe the valve broke is side? If your in a very cold area you could consider blowing the lines out with air. Make sure its less then 50 psi regulated not high pressure shop air. then just treat the traps with antifreeze.
Mark & Melissa
2015 Redwood RL38 , Kodiak disk brakes , 17.5" tires , 8K Morryde IS