New winterizing valves

When we got our 2008 BH it didn't have the quick valves on it, had the dealer install some. They put a cheap brand on and have since leaked past the valve and into the hot water heater. I have since gotten the swan valves and today am installing, of course the wall is to thick to install, so am sanding it down so they fit. And the dealer replaced some water line with garden hose looking stuff, so I'm replacing it with better stuff and finding the water clamps to be junk. I'm really starting to think opening up the compartment and turning 3 valves from factory was the way it should of stayed. Just got it all hooked back together, guess what, same problem. Could it be the check valve in the HW itself that has went bad.

I posted on the same problem last week, I just bought a valve to put on the output of the HWH to solve the check valve issue.

I changed the check valve,and am having the same problem, I think I've screwed up when hooking one of the water lines. I've admitted defeat, taking it to the dealer next week. Shop rate is a little higher when you help themNone.