Here is a picture of my setup:
The canister filter return line goes directly into the top of the reactor. The bottom of the reactor has another line that goes directly into the aquarium. There is no ball valve anywhere in the process. My canister filter is frankly not powerful enough to want any kind of flow restriction or bypass.
I played around with trying to get it to fill without turning it upside down by putting my finger over the return spout in the aquarium (cutting the flow). This did nothing unless I also had an extended air hose attached directly to my co2 airline tube intake (no check valve inbetween) then the water level rose to the level of the air hose. At that point it would go slightly higher then the air hose but water started coming through the line even though I extended the air hose above the level of the aquarium (water pressure was too high for it to be otherwise) - does that make sense?
Anyway bottom line is that for all intents and purposes I was unable to get the water level to rise significantly above the point where the airline tube entered the reactor.
If left running for a period of days the air "should" (in theory) leave the reactor and it should fill entirely with water. This will be due to the air dissolving very slowly into the water. But this will take a while, at least a few days, maybe a week or more depending on how much water is involved. This is just me theorizing, I haven't tried it.
Honestly if it were my setup... I would rip out the hardline pvc connections and redo them with barbed fittings and flexible tubing. Even if you get this problem solved, sooner or later you will have an issue that will require you to drain the tank etc and then your reactor is down for the count till you resolve the problem a second time. Better to deal with this problem now when all your plants won't be dead/covered in algae by a week long delay in getting co2 back up.
Thanks for the detailed post definitely will come in handy when I get everything together.
When I can I'm going to be changing out my tidal 110 for a canister filter because I can run an inline reactor without other things in the tank.
I could get everything running with what I have + soft tube, but I have my doubts about getting a stable Co2 level with my HOB setup on my 55 gallon.
This is my first large tank that I've actually tried to get everything working stable high tech without a canister filter so it's been a learning experience of what works and what doesn't.
So far I've got my drop checker changing to green, but I've already seen it switch between green and blue today with my current setup so things aren't stable with a diffuser + HOB setup.
Also another question, are the PVC fittings you do have are they 3/4"?
I did a little more messing around with the cerges reactor. That air bubble that forms is solved by turning the reactor upside down until it blows out and it wasn't caused by my pump/fittings as I previously thought. I realize now if I had an air purge button that it wouldn't be an issue.
I solved my rex grigg reactor issue.
Everything is still the same as before with the hard line PVC however I've found a way that I can purge the reactor of air is to hook up the pump to the output for a few minutes until I see no bubbles and then keeping everything under water I can hook it up to the input and everything works as expected no air bubble left in the chamber. Turning the pump off only puts a slight bit of air in the system that blows out in about 30 seconds to a minute. I will have to test this on my actual tank, however in my test tank everything seems to be working as expected.