Nicely done. How did you add the threaded opening for the air lock valve? For us warm water pumpers, having the air lock valve at either the three-o'clock or nine-o'clock position would keep max water level inside. Let me know if you will make one for me.
It wasn't bad used a soldering iron slowly melted the plastic until I could thread the couplee while still melted.then let cool with it in and it made perfect threads. I can see what u mean with the coupler in a diff spot would help greatly even could have the option of water lines to replace water with out leaving tube.
Soldering iron - I wouldn't have thought of it. Nicely done. I added a handle to my two-stage because holding it to fill with warm water after I lubed for pumping I struggled for it not to slip out of my grip between trace lube residue and 10 lbs water weight. I carefully drilled the handle holes and managed not to crack the acrylic but didn't know how to do threading.