I rebuilt the Sun Start Chimney pipe with a little more patience and time spent scrounging my garage for better fittings. I was able to find a bronze adapter, but a less expensive piece would have been a 1/2″ SWT to 1/4″ FPT copper fitting. I sweated this together and wrapped it with a few feet of high temp pipe insulation. I also inserted a loose plug of copper scouring sponge down the pipe to reduce fluid loss. I’m looking forward to another sunny day to try it again with the insulated version.
(October 1, 2013) I’ve since told Eldon Haines about this and he built his own out of three-quarter inch copper pipe. I think this is probably advantageous, but we didn’t have enough sun to test it and I haven’t heard from him whether or not it worked. My guess is that it will work better than the half inch pipe because less fluid will be ejected from the end of the pipe. I also found that it does take quite a while for the system to heat up to above atmospheric pressure after you stop the flow through the heat exchanger on the domestic side. The system still has to heat the water that is in the domestic side of the heat exchanger, about a gallon, and that takes some BTUs.