Hot water coming out cold water line

[Kgilbreth]

I have a 2009 2720SL. When I turn on the water heater (Electric or Gas) and wait a bit, I get hot water coming out the kitchen sink when I have only the cold water running. Eventually the water does turn cold, but for the first several seconds, maybe a minute, it's hot. I did some research on this problem in RVs in general, the advise was to add a check valve to the cold water inlet of the water heater. Sounds like a good idea and I ordered one, but upon review of the plumbing diagram at https://www.trailmanorowners.com/for...&pictureid=435 it would appear that this would prevent me from draining the hot water tank via the drain valve.

Interested in knowing if anyone else has this problem and how you fixed it and still are able to drain the water heater.

Thanks!
Keith