Every once in a while an aircraft mechanic has to deal with Chapter 38 – water and waste. The water’s no big deal; maybe a tap that won’t turn on or off, or a coffee maker that pees all over the galley. The waste is another matter.
So, when you get a chapter 38 job, and your lead snickers at you, you can be pretty sure it’s going to involve poop. We all have to do these jobs – if you haven’t done one in a while it means you’re overdue. Or, as I like to say, sooner or later everyone’s number (2) comes up.
I like to be proactive and get the Chapter 38 jobs before they get me. By volunteering to take them on from time to time, I tell myself I’m inoculating myself from getting hit with a truly horrible one.
In future posts I’ll share some hilarious but also gross stories of my Chapter 38 experiences, but first I want to demystify airplane toilets, because I have gathered, based on internet lore and conversations with friends, that there is a lot of curiosity and misinformation out there about airplane toilets.
There are two main types of airplane toilets – blue juice toilets and vacuum toilet systems.
A blue juice toilet is essentially a porta-potty. It looks a bit more toilet-like because it’s overlaid with a polite shroud of carbon fiber and stainless steel that protects the passenger from seeing the … leavings of all the passengers who have gone before. When you hit the flush lever on the blue juice toilet it doesn’t really flush, it just swirls some of the blue juice around in the bowl and then sends it back into the tank below. When the plane is on the ground, someone comes and drains each of the porta-potty tanks into a big tanker truck and then refills the tank with fresh blue juice. And, I just realized I don’t know where it goes after that, but I assume it goes into some kind of massive sewer drain somewhere on the airport premises.
As an oddball sidenote, blue juice is very, very corrosive. Very bad for airplane skins. I have asked why they use something so corrosive in a situation where corrosion can be catastrophic, but no one has an answer. Maybe a product that can deal with human effluvia needs to be corrosive to do its job.
As another oddball sidenote, Patrick Smith, author of Cockpit Confidential, wrote a beautiful and hilarious piece about a blue juice toilet mishap. You can read it here.
Most newer planes are fitted with vacuum toilet systems. A vacuum toilet is a little bit like a home toilet, but made of aluminum instead of porcelain. It’s connected by a pipe to a waste tank at the back of the airplane. When you hit the flush lever a small amount of water washes through the bowl while a vacuum pulls the contents back towards the tank. When the plane is on the ground or below 16,000 feet, the vacuum is provided by a powerful fan. When the plane is above 16,000 feet the vacuum is provided by the difference in pressure between the inside of the airplane and the outside.
When the plane is on the ground someone comes and drains the main tank (or, in the case of wide-body planes, the two tanks). After the tank is drained it’s serviced with a small amount of blue juice, supposedly to disinfect things a bit.
The truck for the blue juice toilets and the vacuum toilet systems are the same, but for blue juice, they will go to a panel under each toilet and drain that toilet directly, whereas for the vacuum system, it’s just the main tank or tanks.
All vacuum systems have a vent that opens to the atmosphere. I quickly learned to stay away from the vent, especially when the plane is being cleaned, because every time the toilet flushes, you smell the ghosts of millions of passenger poops.
If you’re still reading, and you’re curious about how the drains work, and whether poop-sicles are really a thing, read on.
The lavatory service trucks have a large hose that goes over the drain fitting on the plane and turns to lock into place. If everything is working correctly the drain won’t open until the hose is firmly attached, but sometimes things go awry and the lavatory people get covered in poop. I have had to use the service trucks a couple of times while troubleshooting drain issues, but fortunately I have not experience a poop shower. There are some mechanics’ urban legends about poop geysers caused when someone tried to use airplane pressurization to clear a drain line clog, but I haven’t seen it with my own eyes (and hope I never do).
As for poop-sicles (like the one in this scene from Joe Dirt), there’s a myth that pilots dump toilets while in the air, but that doesn’t really happen. It can’t happen because the mechanism for opening the drain is on the outside of the plane.
What can happen is that the drain panel will leak a bit, the, er, output will freeze on the outside of the plane (because it’s really cold up there) and then the resulting poop-sicle will break off and fall to Earth. This can happen, but it’s very rare. According to this article on Wikipedia, there were 27 incidents between 1979 and 2003.
That wraps up my explanation of airplane toilets. I’ll end with a public service message: please don’t put anything but TP and your … product into airplane toilets. If something falls in, don’t try to flush it away, just leave it and let a flight attendant know. He or she will lock out the toilet and let maintenance deal with it at the next ground stop. If you try to flush it, it will get stuck partway down the pipe and create a day of misery for some poor mechanic. And for the love of all things decent, don’t flush diapers.
If you’re not already completely grossed out, check back for stories about my own Chapter 38 experiences.
Aircraft toilets are also covered with a non-stick coating to ensure the bowl is emptied completely