Rhodes just blow through it...air will only go in one way. I have just tested my 1 sided version, i used 3/4" and for the down I used 1 1/4" , it won't keep up with a rio 800 running through 5 ft of flex hose.
My T is about 8" below level of my interior u tube. I don't know what gives this pump only good for 211GPH...
By the way i haven't installed check valve yet either, just siphoned til water came out of my open upright. On the upside it did restart after 10 minutes of sitting, just slower than molasses.