Wilbur, I wish I could advise you on your pressure question, but I can't. Someone should be able to though. I would like to ask that you post a picture of the circulators when you have a minute. I'm curious to see what they are, plus it might help someone answer your pressure question, too.

You can either use Photobucket. Flickr, Picasa or the like or email pics to poolforum@gmail.com and reference the URL of this thread.