Problems with pee tubes include freezing up, and pee causing tail components to rust. I've had both happen. A catheter and bladder both exploding at 17,500 over the whites is not that fun! That's what led me to an onboard system.

All this joking aside, having some pee system and the ability to use it in the cockpit should be mandatory before going off cross country. If you can't pee, you won't drink, and if you don't drink, you can't think.

John Cochrane