Hi!
I wrote a small calculator to optimize drains because I did not find any working tools, just dead links. Just finished it so it can have bugs. Please let me know if something goes wrong for you or you are the hoster of helpbot to integrate this script into the bot. Feel free to use it and spray the word
http://blog.grrbrr.de/drains/index.php
Greetings, Grrbrr404