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I have a radiant floor heat system. One of the zones has 10 loops (covering the master bedroom, master bathroom, and master closet as well as an office and a guest bathroom). The two zones on the left of the manifold have no or very, very little flow. These two undoubtedly run to the bedroom as the floor farthest away from the manifold is cold and with the current cold snap (-20*F), needless to say the bedroom is cold. The valves on the return have checked good (swapped with zones that were working and verified the valves were good). My best guess is a kink or obstruction (air?) in the loops and was wondering if I could try purging them with compressed air and, if yes, what psi should I use? Any other ideas? I do not have access to the loops without removing the ceiling in my basement workshop and of course want to avoid this if possible. Thanks for any help offered!