I always pressure test my radiant tubing, after installed and before the finished floor or concrete covers it. Not only do I test it but keep it under pressure while the rest of the work continued. In the past one heating guy I know would test the system after installation and then remove the pressure once he was satisfied. A big mistake, The electricians came into the job and dropped a staple on the floor and then unknowingly stepped on it. Of course it was on top of the PEX, but no one noticed or didn't want to be the one to do it and so it went un-noticed until the floors were completed and the system was filled with water. Each trade blamed the other but in the end the heating guy had to fix the problem, after all it was his pipe. Keeping the lines under pressure will make it easy to identify leaks before you cover them up and air is a much better thing to have leaking in your house than water. You can find pressure/filler kits on line but most retailers and big box stores don't have them readily available as I found out today. I ordered a couple of the filler/pressure fittings to finish up an install and get it ready to be covered with concrete, but the supplier shorted me one of the fittings and it took me several hours of searching plumbing supply stores to find the fix. Home depot and Lowes don't have these fittings and even the plumbing supply house had to make it up out of several different parts. When doing a DIY install don't forget this very important step, plan ahead and the results will be much better than they were for my friend.
Tom Pittsley
ecobuilder@aol.com www.eebt.org