Right, but based on his username it looks like he's got a Centurion, and for some strange reason they use a Jabsco just for filling AND sprinkler valves AND aerator pumps for draining. I'm guessing he's just going based off of what the factory installed, thinking they know best (turns out in this case they definitely DO NOT).
Honestly, if you're looking to expand your ballast, I would just replace the factory system. It's such a mess that you'll save money and have a lot easier install that way. We've helped an number of Centurion owners with this upgrade and the difference is night and day.