I now have hot water again at both the main house and the lake house. As I posted a couple of days ago, the water heater at the main house developed a leak and had to be replaced. Since it was an LP water heater and was also under warranty, I called in the pros to replace it.
Meanwhile, at the lake house I had to repair the hot water pipes that were cut during the demolition prior to the big HVAC project.
It was fairly simple, I just had to install two 3/4″ SharkBite valves and then use two 90 degree angle fixtures plus some 3/4″ pipe to connect them. It was a little bit more dramatic than it needed to be because I forgot to turn off the valve coming out of the water heater and thus got soaked with water when I cut one of the old valves off, but in the end I achieved victory and hot water was restored.