Hot water bypass stopped working

[skloon]

So went to winterize on the weekend and turned the valve on my 92 Sunflyer- it was still letting water into the tank so I pulled the valve and it did shut off- there is such a spaghetti pile of plumbing I cannot figure it out- can these valves go bad ? it is a ball type one

[Oz]

Ball valves normally work very well for a long time.  However, a particle of foreign matter can interfere with its operation. It may be only that. 

Hm?

[Elandan2]

If your bypass has only one ball valve, it could be the check valve on the other end of the bypass hose that is not closing properly.