Could anyone tell me where the air check valve is?
If it has one it will be in the equipment area. Look for a hose 3/4" that looks like a couple loops with a check valve inline. If it has this then it already has the hartford loop. The one that fails has 3/4" hoses coming out of the top and side while the other side has a 1/4" hose. If you have this one replace it with the hartford loop and your leak from the screen hole should stop.
I have identified that I do not have the Hartford loop installed. Can I just walk in to the Spa store and ask for this Hartford loop? From my limited research, the Loop seems like more of a method instead of a device.