Bob and Doug:
(hey when are we going to hear you two sing your version of the Twelve Days of Christmas, or was that a different Bob and Doug 
) The John Guest company is the one who came up with the "speed fit" style of tubing connector. These are the ones that you just push the tubing into the fitting, and it is permanent (until you take it off), leak proof, etc. No "threaded compression turny thingies" (technical term) just "pushy-inny thingies".
Kari, I tried Western Pump, and they only carry them up to 3/8" and I needed a 1/2" to 3/8" reducer union, so they couldn't help me there. I tried calling a place called "Western Polymers" which I thought might be "Western Plastics" but I don't think that was them ("No we do not sell valves.") I still haven't found a phone number for Western Plastics ... dunno why they're not in the book.
I was looking at some of the other things the JG company makes, and one thing that they make is a speed-fit checkvalve, another is a 2-way divider which is more like a "Y" fitting and might be a little more optimal than a "T" fitting for the calc reactor recirc-line/input-line..
Here's the page I was looking at
John Guest Fittings
I guess there are a number of different places online too, all I did was go to the first link I found mentioned at RC but there are others too (
www.mcmaster.com ...
http://www.portagespecialty.com/custom/JohnGuest.html ... also Wendell mentioned a place called "Farris Enterprises" to me). The usplastics.com site seemed complete enough, we'll see how long it takes them to mail a couple bits up to Canuckadaland...