Here are some links to general information that you may find helpful for DIY plumbing and heating work.
This book has a lot of information about copper tubing. If you have dial up be warned the file is about 6.5 mb.
http://www.copper.org/resources/pub_lis ... ndbook.pdf
If you like copper for other things too check out their web site.
Here is a link to Colder Product Company who has a white paper out about those mysterious pipe threads. It’s only 6 pages but they want you to give your name and address before you can download it. (PIA! But it is worth reading)
How to figure heat output of a radiator? This has good information on the last few pages about that.
And finally here is a web article about gravity hot water systems that I found interesting.