The blower needs to sit at least 24" above the waterline of the spa. It should also have a check valve with a very soft spring 12" below it to prevent back flow.

It is normal to see water in the line when the system is off but not normal for it to rise up the pipe unless the jets are closed in the spa. What kind of spa jets do you have?

Scott

Since it works when pulling water from pool, and not well from spa, I would think there is some blockage in the spa suction. Maybe pipe mouth to close to drain cover, or wrong size drain cover, or they left a sponge in there.
Thats the line they should be blowing/inspecting.

I'll put my bet on improperly sized eyeballs, or a sponge back in one of the jets.

The eyeballs should have at least a 3/4" opening

I would remove all of the eyeball fittings, and turn the blower on in pool mode. Make sure air comes out of all the jets If one of them doesn't have air its, more than likely your problem.

If air comes out of all of them, with the eyeballs out of them, turn off the blower and put it in " spa mode" and feel each jet for water. If there is water coming out of each jet (and relatively equal flow), turn on the blower then see what happens. If the jets work well you need to get larger eyeballs.

its possible that they plastered over a jet as well.

Nicole,
Maybe I misunderstood what you meant by pool mode.
I assumed you were in a spillway mode, and turned on the jets directing water to the jets, but feeding from the pool.
If this is the case go for my idea, if not listen to racket.
IE:
If you are turning on just the air (no water), and get plenty of air, but then turn on the jets (water) and air goes away then eyeballs it is.