Dont just let it keep going like that! You can always pull bubbles. You have to watch the size bubbles, the smaller ones in the beginning are C02 and after that you are ust pulling o2 through your wine. I use it on low for about 3 minutes, then try and goup to 18 and if I can I shut it off and max the adjuster at the same time and it wil hold a vacuum that way wih the exception of the wine degassing, once I can hold 16" for 1/2 an hour its deassed. You have to have some cotten in the exhaust port to do this as resistance and you have to have enough of it.