Yesterday, I installed coiled-up copper pipe inside the steel water tank, and rigged it up to the solar hot water panel. After that, I got it insulated. Not perfect, but fairly good, still knowing I need to be able to get inside the tank some more.
Yesterday afternoon, the weather clouded up around 3:30, and then we had the first real thunderstorm of the year, which seemed to go on all night. This morning, it's cold (50F) and rainy, with no sun whatsoever.
So how is the water? I first checked the thermometer on top (with the tip punched straight throw the insulation and into the water) but the lowest the kitchen meat thermometer goes is 120F. So, I knew that the water was at least a little lower than that. Next, I peeled back the insulation on the lid to slip my hand inside. The water was WARM! I would estimate it to be around 100F. Nights right now are in the high 30's to low 40's. Before, with NO insulation on the 55 gallon drum. The water would be COLD in the morning. Last week was a little colder, and there would actually be ice on the top of the water drum.
So, from frozen to warm with only a small change in weather - wow, what a difference insulation makes. And it wasn't even perfect. The insulation is NOT sealed up as well as it could be. In fact, in the finished version, I intend to seal up every last crack with expanding foam, and the tank will have MORE insulation than a standard hot water tank would have.
Also, right now, the tank is in my backyard. Having it in a 68 degree house should make a fair amount of difference as well.