primary secondaryq

Don Tauer

I have a radiant system where the 1-1/4" secondary loop is above the 1-1/4" primary loop. What is the proper way to install a thermal trap between the two systems? The better way would to have the primary above the secondary but this is not the case here. It feels like the heat is creeping right up the 1/2" pipe to the tee where it joins the secondary loop but the secondary loop is cool, well 82f. Is this 170 degree water sneeking in or does it stop at the tee when the injection pump isnt running?