My Stenner pump came in yesterday and now I am ready to install. I plan to tap into my return line somewhere downstream of my heater. My question is: should I tap into the PVC pipe or should I tap into a PVC fitting (90 or elbow)? The PVC fittings are thicker than just the pipe and therefore should allow my plastic for me to cut threads and make a more stable injection point. But I may be overlooking something. Any advice? I don't want to mess this up.