The pump with bags I've bought to store and bought in large quantities of cat food airtight. The pump works in the system is actually very good. The air may be sufficient to drain. But five 3L bags remained only one more than 30 minutes actually sucked. The other I have repeatedly closed and sucked off again. All picked up again for air. The "good" bag was sealed even after a week. At about 2 per bag, I find such a lottery process rather unpleasant. Unfortunately, bringing the pump without good bag not much.