Why won't my tub drain?

[snoopydance]

I'm the one with the Saratoga Spas/Adirondack Saranac (used) sitting in my driveway. The gravel pad is now complete, an insulating heat shield piece of insulation is cut and ready to go, and the electrician is scheduled for Wednesday. Between now and then, we have to move the tub about 15 feet over lawn. I figure 8 people, 2 on each side. Wish me luck!

BUT. My tub has been gathering rainwater. (I didn't cover it because I didn't want it to grow things like a refrigerator that stays closed.) The other day I opened the two faucet fittings on the end of the drain hose and drained the water out. No problem.  Today it wouldn't drain.

There was about 4 inches of water in the bottom. We plunged it, to loosen up anything that might have gotten stuck in there, and as we plunged, little spurts of water would come out. I don't think it's debris. I think there's an air bubble. My earlier life as a tropical fish enthusiast made me think of starting a siphon, but I was afraid of what might be in that water.

Any ideas? I can take a picture of the 2-faucet setup that the previous owner installed. He had the tub on his deck and drained it right into a drain into the woods. I don't remember what he said about why he did the 2-faucet setup. I ended up bailing it and wiping it out with a sponge.  

Also, between now and Wednesday, should I put the cover on with a couple of tennis balls keeping it open or keep the top off altogether, like it's been?

[Mr._Bubbles]

I’m not sure about the drain, probably a clog or air bubble like you said.  Maybe try to vacuum the drain/jets.

I would not leave the cover off, without water in the spa.  Extreme heat can build up and cause problems with the shell, plumbing and so on. You can vent the Spa Cover, like you said.

[kacrab10]

Our cover was on for a long time without water and nothing grew. We still did the whole fill/purge/fill cleaning afterward but it is much better then getting leaves, grass and other dirt/bugs in there.