Might be worth pouring a bit of non toxic RV anti freeze into the sink trap and toilet when you leave, just in case.
If your water line runs to the lake, do you heat the line all the way? Does the ice move and risk taking the line with it?
One of the things we found heating a cold camp in the spring and fall was that it takes a lot of BTU to raise the temperature of the mass of the structure. It can take a while if you don't have a lot of excess heating capacity.
Enjoy the extended season.
|