Originally Posted by drvannostren

Incorrect. 737s, the backbone of many airlines, still use blue juice. They might not use as much as before, but they still use it. I'm a ground handler, just serviced a 737 lav 20 minutes ago.

The problem is people flushing the wrong stuff, and/or many other things including lavs being serviced incorrectly. 757/767s are a pain in the ... to service and have multiple lavs, inexperienced lav guys often miss one. Or people who don't deal with these aircrafts that often will easily miss one. But that usually doesn't result in ALL the lavs failing.