Bypass valve failure

[Greenman]

After two weeks of -20 C weather we had a chinook blow in last night and temperature jumped to 0 C overnight. When I went out this morning I noticed a bunch of pink fluid on the ground just under the exterior water heater door of our EXP 213. I opened the door and found RV antifreeze leaking from the hot water tank drain. After I drain the tank in the fall I usually put the plug in only one or two turns so its loose in the drain hole. But with the winterizing bypass on there should not be any antifreeze in the tank. I open the trailer and crawl under the slide out and cannot find any fluid on the floor anywhere in the trailer. Plug the trailer in and run out the slide so I can look at the tank and bypass valves. Inspection reveals that about 6 inches of water line adjacent to the top bypass valve is empty of antifreeze. The top bypass valve handle is loose in the fitting and rattles loosely as I turn it on and off. No external leakage. The bottom valve is tight. Obviously the top valve failed. Perhaps residual water in the valve freezing. I inspected all the rest of the lines in the trailer and they are all still full of antifreeze and no leaks anywhere. Looks like I will have to replace a bypass valve come spring. I also found out the smoke detector was beeping from a dying battery, got that taken care of.