I winterized my 3170 a couple of weeks ago. I wanted to add some valves so I could shut off my outside shower for an upcoming winter trip. I added the valves and wanted to check the system for leaks.
I closed all the open vavles and put the plug back in the water heater. I repositioned the water heater bypass valves so the water heater was back in the loop. I used my air compressor to put 40 psi into he system, and all appeared fine.
When I checked, I was not getting any air from the hot side of any of the taps. When I pulled the drawers out to confirm the vavles I noticed the pipe in the picture below.
I wondered if that pipe had frozen because it was on the other side of the valve and at an angle that would not drain.
I pulled the heat gun out and after a short time I started to get air from the hot side of the faucets. I left the sytem charged with air while I finished up a couple other things. The system held pressure so I am hoping I am in goood shape.
Thought I would pass this along for others with this setup to confirm that dont have a similar issue.