Blichmann Dip Tube not draining

With a brand new Blichmann 15 gallon Boilermaker - the vale/dip tube were already connected, No assembly other than the Thermometer.

I attached a 3 foot (1/2") silicone hose to the dip tube, with the bottom of the hose 2 feet below the dip tube. (to create suction)
I filled the pot with 7 gallons of water and opened up the valve.
It drained until around the 2 gallon level (already passed the dip tube level) when it stopped. The suction was never broken.

When I tipped the kettle to the side, then the remaining water came out, except for a few ounces.

So I can get my beer out, but why doesn't it drain on its own, down to 0.23 gallons?

It's a new pot, I don't think the O ring needs to be replaced. I can wiggle the dip tube a bit, but it was never removed.

Suggestions?

When you first installed the dip tube, did you insert it till the o-ring is in the groove before tightening the Allen bolt?

>>When you first installed the dip tube, did you insert it till the o-ring is in the groove before tightening the Allen bolt?

It came pre-assembled/installed. No installation necessary. (Other then the Brewmometer)

Pull it out and loosen the Allen bolt on the retaining ring. Slowly slide the dip tube back in until you can feel the o ring slip into the slot, slide up the retaining ring and tighten Allen bolt. This will ensure you have a good seal and siphon won't break. Not guaranteed to fix the issue, but it is one variable.

Ok, thank you

Also try putting a little dab of keg lube in the oring groove on the dip tube