Check whether the sealing ring around the paintball neck in good condition.3. if the sealing rings in good condition, leak happened from the adapter releasing hole when screw the regulator in. it maybe because the paintball sealing ring not at the standard size, the regulator push it off its position. Facing such situaion, we can take the following actions.1. Using oil or water lubricate the sealing ring and the contacting surface in the adapter to avoid it being pushed off its position.2. If leak still happen, we can put a sealing ring in the regulator to sealing it