I went out and bought a drill press this evening along with some silver solder, 200 feet of type M 1/2-inch copper pipe and a fancy hole driller for my header-style heat exchanger project. I got the 1" pex-al-pex to replace 100 feet of my 1" copper (the headers), so I'm about ready to get started. The drill press works well. Since I have about 128 holes to drill, I figured this was a good time to buy something that I always wanted anyway. I also got a new blade for my tube cutter and a stone for reaming the pipe. I agonize about this stuff, but do enjoy planning and doing it. One concern I've had is that I'll get the hx built and installed in the tank, then fill the tank up and find out that the damn thing doesn't work for one reason or another. What if it leaks? I can't really pressure test it before putting it in the tank, because it has to go in in sections and be assembled in the tank. One of those things. Or, what if my design sucks and only part of the hx heats up, essentially crippling it? What do I do then? Well, it occurred to me that I can build the thing, put it in the tank and get everything all hooked up, and then--ta da!--run it for a couple of days in the empty tank to check everything out. Any leaks will be immediately evident, and I can make sure that the heat is being distributed evenly. If not, you guys can help me figure out why not, and we can redesign it. So that's where I'm at with that. Pics to follow.