Hmmmmm. Well, since we don't have an answer yet, I am going to use a air compressor to blow each individual pipe to see the results. Will I see air bubbles in the spa from the outlet? Hopefully. If that doesn't work, I'll remove and disassemble that particular spa jet to see if there is something that is creating a "BackPressure" and routing water up through the air intake line. That's the only thing that I could reasonably conclude with my limited knowledge, that there is some sort of blockage either in the pipe itself, or the jet that does not allow for the proper mixing of water and air. I'll keep posting and updating as I move along.... just in case someone else has this issue in the future!

I read your post but had no earthly idea what was going on (not my area of expertise :) Unfortunately this pool forum has slowed down a lot which is unfortunate. I guess while you are building it's all you can think about and then when the pool project is done you sit back and enjoy. Unless problems rear up, so I keep checking back in to keep learning. Hope someone can help you out.

Thanks for the suggestions. I ended resolving the issue by removing all the waterway jets, and blowing each venturi pipe for at least 30 seconds. All six pipes allowed this to happen, and water only seemed to be in one pipe. After blowing each several times, it seems to have cured the issue. After reinstallation, all six jets seem to be operating correctly with air bubbles. I am guessing that my initial observation may have been correct with debris in the effected jet causing it to back up through the air line.

Now if the million dollar question. How to prevent debris entering in through the venturi air lines? I think that cutting a square of screen and using a rubber band to secure it over the pipes would be a temporary solution but am wondering if any of the Pro's out there have a better suggestion or long term solution.

Thanks again for any of your thoughts!

It's doubtful the debris entered into the air line at the equipment. Check your filter to make sure the cartridges or grids don't have holes and the are secured inside the tank. The debris could have also gotten in there from the last filter clean out.

usually this issue is caused because the jets are not screwed all the way in. when it is properly fully seated it will not allow water into the air chamber. if it isn't screwed all the way in the jets will back pressure backwards into the air line. this is a very common issue which obviously you resolved by removing them and re-installing.