Any ideas to keep my fresh water tank protected from below freezing temps? My tank is accessable though the front storage area.It sits on a sub-floor under the bedroom.I don't believe I can use those heating pads (ultra-heat etc.) since I can't get to the bottom and if I could they would get crushed.I have been told they would not do much sitting on top.Of this I'm not sure?I would be using the 5th wheel in the fall into early December here in northern Illinois.Nights can often fall into the teens or 20's.Any advice would be much appreciated.I'm new at this!