Piggy back ballast bag for surfing on stock system

I would like to add a bag (either tube sac or fat seat bottom) that would run under our port seats for surfing. To do this I was hoping to leverage our current system without having to add new holes for draining, venting, or bringing water in. I could "Y" some of the connections, but would also rather not dick with wiring in more pumps / switches.... but thats just me being lazy.

My though would be this:



It seems to work on paper, but my concern would closing the valve to just fill the rear bag for wakeboarding, but when it comes time to drain, I'll open the valve and let the rear bag flow to the new one .... when it starts to get low though, will the suction from the pump be enough to pull water through the new bag and get it out of the boat, or will I be stuck with leaving a good amount of water in the bag(s).


Thanks for any input or advice!

I'd be concerned about that drain pump, aerator pumps don't really "pull" or "suction" like a impeller pump would. I think you'll end up with a lot of hassle every time you fill or drain

buy a reversible ballast puppy, and get rid of the aerator's