We have seen this issue more and more with taller, larger ballast sacs. First step is isolating which plumbing circuit the passive draining is occurring through. Depending on the pump system, it could fill, drain, vent or any combo of them. Once you isolate the offending circuit, the fix depends on the pump system, ballast layout and how the boat is uses. Crossing the vents and drain lines work for a listed surf boat, but not for those evenly weighted and using a surf apparatus. Check valves can work, again depending on other factors. Manual valves can certainly stock passive draining, but now you no longer have an automated ballast system. id prefer to not use them. Vented loops can work, however, in a vent line application, a vented loop would put the vent line dipping well below the top of the sac. This can create venting issue.