Chapter 38 – Or Airplane Toilet Tech Talk for the Non-Technical

I knew this night was coming, but I didn’t know when. Sooner or later, every mechanic working on transport aircraft will need to deal with Chapter 38.

What is Chapter 38, you ask? Are you sure you want to know? Aircraft manuals are organized by a standardized numbering system, so that on any plane, Chapter 28 will concern fuel, Chapter 35 will concern oxygen and so on. And Chapter 38 … well, Chapter 38 is about water and waste. Mostly waste. Yeah, that kind of waste.

On some airplanes the lavatories (as they are euphemistically called) are self-contained. When you use the self-contained type, you’re sitting on top of a tank of blue water. When you flush, your stuff drops down into the blue water and stays there until it’s pumped out at the next ground stop. You can identify this type of airplane system by the blue water that swirls around the bowl when you flush.

On others, the lavatories are connected by a pipe to a central tank (or they’re divided up between two tanks). When you flush, everything is whooshed out, through the pipe and to the central tank. Then, on the ground the tanks are pumped out. You can identify these by the absence of blue water and by the very loud “whoosh” they make when they flush.

For those who are interested – on the ground the whooshing is done by a vacuum pump, but in the air, the vacuum is provided by the pressure differential between the pressurized cabin and the non-pressurized ambient air outside the plane (but, don’t worry, the stuff still goes to the tank – it doesn’t go shooting out the bottom of the plane).

So, anyway, last night at my internship, I was told I was going to be working “Chapter 38.” Someone had stuffed god-knows-what down one of the lavatories and plugged up the pipe that leads to the holding tank. This meant that instead of whooshing out to the tank the stuff was all stuck in the pipe. This meant that someone was going to have to open up that pipe, deal with all the stuff that had piled up in it and find the clog. I was told that this someone was going to be me.

I asked permission to go to Stores and outfit myself with all their protective equipment, but as I was getting ready to head over to Stores (Stores is the parts and supplies department) one of the mechanics suggested that we go to Home Depot and buy the longest snake they had. So, we did that, and then, probably because snaking involved the risk of damaging the pipes, the two mechanics I was working with took turns snaking, instead of making me do it (though I did offer). I made myself useful by managing the trash, carrying parts and tools in and out of the plane and providing an endless stream of rubber gloves to all involved.

We all had our money on a diaper as the clog culprit, but in the end it turned out to be a huge wad of paper towels. Prior clogs have been attributed to underwear, diapers and soap dispensers. So, next time you fly, please resist the urge to throw anything but the approved items down the lav. Your trusty Chapter-38-fearing mechanics will thank you.