Air control problems in a Caldera Vancanza series spa

[GwenLeBlanc]

The (2.5 year old) tub is draining through a green tipped clear vinyl tube that I am thinking is for air (the water filled tubes at the unions are smaller and purple tipped, these are larger and green at the ends, and don’t connect to anything). Watkins doesn’t explain anywhere that I can find what the color coding means, this is just a guess.  I can’t follow the tube far enough back as it disappears under the tub, but I can fairly certain through trial and error that it connects to one of the air diverters.  
 

I was reading (here, thanks very much fellow enthusiasts) that overfilling can cause an issue with the air control valves.  I have had a problem with the cover leaking at the center seam, but was all eh, more water more fun! and put a new cover on my things to buy later list without too much worry, and just removed excess water after particularly bad storms (very frequent in my part of the country at this time of the year, we get more rain than Seattle).  Anyway it always seems to drain to the same level (about half way), and fairly quickly, pretty much at the same rate as if I had been draining the tub deliberately.

It’s full right now, after my last round of fiddling with it, I have (what I think is an) air hose raised so that (what I imagine is a) siphon effect isn’t working anymore.  The tube seems to fill slower with the diverter open all the way (that one is generally kept closed).  I can add pictures of the spa if they might be helpful, but right now it’s just a picture of a hot tub.

My question is, (besides a new cover to keep out excess water), what can I do to stop it from happening?  Will it stop if I change the air control valves on the side? Is it likely to cause more problems?  The water temperature had dropped significantly, I was assuming because of the missing water (the water that was still there was still circulating) and it seems to be coming back up to temperature.  I’m a little panicked because of the holiday weekend and the weather (although we are having pretty mild weather for the time of year, it’s supposed to be in the fifties all week).  

[In Hot Water]

The tubing goes to the floor drain suction fittings for the vacuum brake. If you blow into them you will see air coming out of the intake fittings. There is a diaphragm flap that opens up when the  floor drains are blocked. This keeps an entrapment from occurring. When the diaphragm deforms, the water will seep up the vent tube, and eventually start a siphoning process. Extend both of the tubes above the waterline, and it should solve the problem.