I fill it with a portable pump - the new Sum Max Flow Ballast Pump. Eventually I would like to piggyback it off the center bag but currently this is what I use. Fills really fast too - like 5 minutes although I have not timed it. BTW, the link fill port on mine is on the port side not in the front like the picture shows. I bought it anticipating it being on the front of the bag but it is on the side.