If we suspect lids are a problem, we grab some of our Waytek ty-wraps & double-tye the lid. This was certainly a task to do if someone had removed the lid to "add" bags of corn/beans. We get all of our corn & bean seed in pb.

The lids are probably not waterproof. I'm wondering if lids on pure bulk tanks are waterproof?? Our PB lids seem water resitant enough....IF you're sure the lid is fastened at all available points. Just using the "center" positions for tye-wrap placement doesn't seem enough...we need to make sure all positions are tyed if going for long road transport. Maybe we don't drive as fast as most people though either.