Not sure if this is actually a bug or just a feature that hasn't been improved yet. When curating a colony or only vomiters you can easily operate at 100% stress levels while also producing water from the vomit. (Just build vents to let it trickle down) My colony has been at 100% stress for the last 30 cycles and survives off of only contaminated water and dirt.
Interestingly enough after not using an outhouse for 20+ cycles and finally building a lavatory my dupes refuse to use the lavatory even though it is easily accessible and has water flowing in and out.
Steps to Reproduce
Kill off all your destructive dupes and only spawn ones that vomit. Don't build an outhouse for a long time. (20ish cycles)
This issue has not been confirmed by a developer yet.